UK domestic air conditioning: a study of occupant use and energy efficiency

This paper presents the results of a study of air-conditioning usage in homes in the southeast of England. First part of the study consisted surveying 13 dwellings with air-conditioning for a series of 4 week periods during the summer of 2004. The second part involved testing energy efficiency of “single-split” and “portable” air-conditioning units under “in-use” conditions. Data on usage patterns and typical temperature profiles during operation was collected and is presented here. Temperatures at which users switched their units on were, on average, 24-25oC, while typical running times for a single operation were found to be around 5 hours during daytime and 7 hours at night in bedrooms. The study also indicated high occupant satisfaction rates with split-units. An unexpectedly high overall energy efficiency ratio (EER), of 5-10, was found for the single-split unit tested during the relatively mild autumn weather. However, a very poor EER, of less than 1, was found for the portable unit tested. Further work is needed to increase the reliability and statistical significance of the results

The construction of self-dual normal polynomials over GF(2) and their applications to the Massey-Omura algorithm

Gaussian periods are used to locate a normal element of the finite field GF(2e) of odd degree e and an algorithm is presented for the construction of self-dual normal polynomials over GF(2) for any odd degree. This gives a new constructive proof of the existence of a self-dual basis for odd degree. The use of such polynomials in the Massey-Omura multiplier improves the efficiency and decreases the complexity of the multiplie

Health and Inequity: A Socio-Cultural Analysis on Food and Nutrition Among Students

Food is not just a biological need but it is very much social in nature. Socialization and culture has an influence on the eating habits as culture plays a significant role in our daily food choices and diet. The present study endeavors to create an awareness on the effects of unhealthy food habits which are developed by the students due to one’s culture or enforced by an organization. Undergraduate students pursuing education at University of Eswatini are considered ensuring or seeking information that will be helpful in the research. Nutritionist in the academic sphere is consulted to interpret the data looking into the health perspective and predict the threats imposed by the food culture health-wise. The study revealed that most students eat twice a day and some once which is not advisable and recommended by dietitians and nutritionists, because this can obviously lead to malnutrition and under nourishment. The developed culture of eating in the institution, happens to impose an unhealthy hazard to the health of students. One of the major challenges of students is that they are not permitted to cook for themselves in the institution (dormitory), which exposes students to junk food, hence the future health complications, like obesity, diabetes, cardiovascular diseases and many other diet related illnesses or conditions. The research recommends reframing university rules on cooking, provision of meals on fixed time and nutrition based education should be provided by the institution

Experimental characterisation of rate-dependent compression behaviour of fibre reinforced composites

Fibre reinforced polymers (FRP) materials are being increasingly used for aerospace and automotive structural applications. One of the critical loading conditions for such applications is impact, consequently, understanding of the composite behavior under such loads becomes critical for structural design. The analysis and design process for achieving impact-resistant composite structures requires rate-dependent constitutive models, which, in turn, requires material properties of the composite over a range of strain rates. It is, therefore, the objective of the research to investigate the strain rate-dependent behavior of fiber reinforced composites under compressive loads for a wide range of fiber orientations. Quasi-static (≈ 1e-3 s-1) and high loading (≈ 200 s-1) rates are considered for the experimental study. Accordingly, two different test setups are utilized, a screw-driven universal testing machine for quasi-static tests and a Split Hopkinson Pressure Bar (SHPB) system for dynamic tests. The stress-strain response of the composite is reported for the different fiber orientations and the strain rates, revealing the rate-dependent characteristics of the carbon fiber reinforced composite. From the test results, it is observed that, the dependency of the fracture strength on the loading rate is significant. The results are summarised in terms of the failure envelope in the transverse compression-in-plane shear σ22-σ12 plane for the two strain rates

On generalized Lagrange–Hermite–Bernoulli and related polynomials

We introduce a new class of generalized polynomials, ascribed to the family of Hermite, Lagrange, Bernoulli, Miller–Lee, and Laguerre polynomials and of their associated forms. These polynomials can be expressed in the form of generating functions, which allow a high degree of exibility for the formulation of the relevant theory. We develop a point of view based on generating relations, exploited in the past, to study some aspects of the theory of special functions. We propose a fairly general analysis allowing a transparent link between different forms of special polynomials

A Wedge-DCB Test Methodology to Characterise High Rate Mode-I Interlaminar Fracture Properties of Fibre Composites

A combined numerical-experimental methodology is presented to measure dynamic Mode-I fracture properties of fiber reinforced composites. A modified wedge-DCB test using a Split-Hopkinson Bar technique along with cohesive zone modelling is utilised for this purpose. Three different comparison metrics, namely, strain-displacement response, crack propagation history and crack opening history are employed in order to extract unique values for the cohesive fracture properties of the delaminating interface. More importantly, the complexity of dealing with the frictional effects between the wedge and the DCB specimen is effectively circumvented by utilising right acquisition techniques combined with an inverse numerical modelling procedure. The proposed methodology is applied to extract the high rate interlaminar fracture properties of carbon fiber reinforced epoxy composites and it is further shown that a high level of confidence in the calibrated data can be established by adopting the proposed methodology

Evaluation of FAOAqua Crop model for wheat under different irrigation regimes

The experiment was conducted at the research farm of the Water Technology Centre, IARI, New Delhi during rabi seasons of 2010-11and 2011-12. Irrigation treatments include irrigation applied at 50% deficit (W1) and 25 % deficit (W2) and full irrigation (W3) under recommended fertilization levels with split doses of N-fertilizer. Fullirrigation treatment was based on irrigations to meet the soil moisture deficit up to the field capacity (FC) level and deficit irrigation treatments of 25% and 50% were imposed with respect to the full irrigation.The model was calibrated with experiment generated data sets of rabi 2010-11 and validated using the data set of rabi 2011-12. It was observed that the validated model performed well for grain yield prediction with absolute prediction error of 2.9%, 0.91% and 7.85% for full, 25% deficit and 50% deficit irrigation levels, respectively. Also, for prediction of biomass yield the prediction error ranged from 11.81% to 28.96% for all three irrigation treatments. Moreover, the validated model was observed to predict the water productivity with absolute prediction errors of 43.57%, 13.87% and 12.8% for full, 25% deficit and 50% deficit irrigation treatment levels, respectively. Nonetheless, it was observed from this study that the AquaCrop model can be used to simulate the grain and biomass yield for wheat crop with acceptable accuracy under different irrigation regimes in a semi-arid enviroment

On the Rate-dependent Plasticity Modelling of Unidirectional Fibre-reinforced Polymeric Matrix Composites

Three different approaches to plasticity are investigated to model the experimentally-observed non-linear behaviour of unidirectional fibre-reinforced polymeric matrix materials. The first and simplest approach consists on assuming independent one-dimensional rate-dependent plasticity on in-plane (12) and through-thickness longitudinal (13) shear components of the Cauchy stress tensor. The second, employs a 3D extension of the plane stress Hill'48 anisotropic plastic surface. The third and the last is formulated as a quadratic yield function inspired by Puck's fracture initiation criterion. It searches for a plastic localisation plane in which a certain combination of normal and shear stresses is maximum. Numerical simulations are conducted to analyse the off-axis compression behaviour of carbon fibre reinforced epoxy composite under varying loading rates. The afore-mentioned three different approaches are explored with an aim to predict the experimentally-observed non-linear response of such composites. The model parameters are determined using a deterministic inverse modelling strategy employing an iterative domain reduction optimisation technique. As far as the experiments are concerned, the quasi-static and medium rate tests were carried out in universal testing machines, while the experiments at high rate were conducted in a Split Hopkinson Pressure Bar system. The effectiveness in terms of accuracy and robustness of the three approaches are discussed