Derivations and Centroids of Four Dimensional Associative Algebras

In this paper, we focus on derivations and centroids of four dimensional associative algebras. Using an existing classification result of low dimensional associative algebras, we describe the derivations and centroids of four dimensional associative algebras. We also identify algebra(s) that belong to the characteristically nilpotent class among the algebras of four dimensional associative algebras.Comment: 20 pages, 2 tables, Accepted in International Journal of Pure and Applied Mathematic

Environmental performance of Abuja’s low-income housing : understanding the current state to inform future refinement

In times of global ecological challenges, understanding building performance to improve occupants’ comfort is becoming the norm in various climatic zones and locales. Any performance evaluation should account for occupants’ demands for thermal and visual comfort. However, seeking to analyse the impact of design on the two aspects of comfort simultaneously can be complicated especially when a series of parametric changes with varying impacts on either is necessary. In the Nigerian context, assessing the environmental behaviour of existing residential properties to inform future refinement is becoming far more critical due to the vulnerability of the region to the changing climate, the ongoing issue with the energy supply and the housing shortage. The method adapted in this paper following previous research can be useful for the coinciding evaluation of the thermal environment and visual comfort. The environmental behaviour of two of Abuja’s common housing types, in their current state and with the addition of multiple shading elements was assessed using such methodological procedures to examine their suitability for performing a comprehensive analysis. The paper discusses the simplicity of the graphical representation utilised in displaying the changes in the cases’ behaviour following the alteration. It also provides an insight into their current performance. KEYWORDS: Housing, Comfort, Methodology, Nigeri

Remodelling façade design for improving daylighting and the thermal environment in Abuja’s low-income housing

The housing typologies that were developed as part of Abuja’s master plan over 30 years ago are still in use today as prototypes for low-income housing developments. The value of the local climate received only cursory consideration in the early developments; as the process was mainly focused on the delivery of units needed to accommodate those involved in the construction of the city. More detailed records of the climate have become available since the mid-1990s. Yet, despite the availability of such data and the global interest in eco-friendly architecture, energy use per household has increased in Abuja over the last two decades. Nigeria is already struggling to meet its current energy demands; therefore, it is important to examine whether improvements made to future housing design can assist in reducing their energy use. This paper evaluates the performance of four of Abuja’s common housing types and examines the impact of changing their fenestration design on occupants’ comfort, using validated simulation. Assessing the performance of the buildings in their existing state revealed clear overheating problems and excessive natural lighting. However, the investigation indicated a 4-6% reduction in the frequency of thermal discomfort and a 4-29% reduction in visual discomfort by adjusting the orientation of the facades. Integrating external shading components can also reduce thermal and visual discomfort by up to 4% and 29%, respectively

Empirical analysis of rough set categorical clustering techniques based on rough purity and value set

Clustering a set of objects into homogeneous groups is a fundamental operation in data mining. Recently, attention has been put on categorical data clustering, where data objects are made up of non-numerical attributes. The implementation of several existing categorical clustering techniques is challenging as some are unable to handle uncertainty and others have stability issues. In the process of dealing with categorical data and handling uncertainty, the rough set theory has become well-established mechanism in a wide variety of applications including databases. The recent techniques such as Information-Theoretic Dependency Roughness (ITDR), Maximum Dependency Attribute (MDA) and Maximum Significance Attribute (MSA) outperformed their predecessor approaches like Bi-Clustering (BC), Total Roughness (TR), Min-Min Roughness (MMR), and standard-deviation roughness (SDR). This work explores the limitations and issues of ITDR, MDA and MSA techniques on data sets where these techniques fails to select or faces difficulty in selecting their best clustering attribute. Accordingly, two alternative techniques named Rough Purity Approach (RPA) and Maximum Value Attribute (MVA) are proposed. The novelty of both proposed approaches is that, the RPA presents a new uncertainty definition based on purity of rough relational data base whereas, the MVA unlike other rough set theory techniques uses the domain knowledge such as value set combined with number of clusters (NoC). To show the significance, mathematical and theoretical basis for proposed approaches, several propositions are illustrated. Moreover, the recent rough categorical techniques like MDA, MSA, ITDR and classical clustering technique like simple K-mean are used for comparison and the results are presented in tabular and graphical forms. For experiments, data sets from previously utilized research cases, a real supply base management (SBM) data set and UCI repository are utilized. The results reveal significant improvement by proposed techniques for categorical clustering in terms of purity (21%), entropy (9%), accuracy (16%), rough accuracy (11%), iterations (99%) and time (93%). vi

Characterization Of oil/ gas flow pattern in vertical pipes using electrical capacitance tomography

Electrical Capacitance Tomography provides the opportunity to visualize the contents of a process of many applications such as pipeline and obtain information on the flow configuration. Multiphase flow is an extremely complex field of fluid mechanics; the characteristics of the operations of many equipmentin different areas of industry such as oil and power generation are determined by the nature of flow of two phase or multiphase. In this study, a twin plane Electrical capacitance tomography (ECT) electrode was designed, fabricated and used to image and characterize oil/gas flow in 67 mm pipe. The experiments were carried out in inclinable facility in the Department of Chemical Engineering at Nottingham University, UK. Conditions used are gas superficial velocities of 0.05 to 5.52 m/s and liquid superficial velocities of 0 to 0.54 m/s. The cross-section averaged void fraction and its variation in time were measured using electrical capacitance tomography. Also, Probability Density Functions are demonstrated and the structure velocity of flow is presented as well. In this project, Bubbly, slug, and churn flow configurations was observed. In addition, high speed video images of flow were obtained simultaneously and compared with tomographic images of the ECT system

Aperture-Coupled Asymmetric Dielectric Resonators Antenna for Wideband Applications

yesA compact dielectric resonator antenna (DRA) for wideband applications is proposed. Two cylindrical dielectric resonators which are asymmetrically located with respect to the center of a rectangular coupling aperture are fed through this aperture. By optimizing the design parameters, an impedance bandwidth of about 29%, covering the frequency range from 9.62 GHz to 12.9 GHz, and a gain of 8 dBi are obtained. Design details of the proposed antenna and the results of both simulation and experiment are presented and discussed

Design of Frequency Reconfigurable Multiband Compact Antenna using two PIN diodes for WLAN/WiMAX Applications

YesIn this paper, we present a simple reconfigurable multiband antenna with two PIN diode switches for WiMAX/WLAN applications. The antenna permits reconfigurable switching in up to ten frequency bands between 2.2 GHz and 6 GHz, with relative impedance bandwidths of around 2.5% and 8%. The proposed antenna has been simulated using CST microwave studio software and fabricated on an FR-4 substrate. It is compact, with an area of 50 × 45 mm2, and has a slotted ground substrate. Both measured and simulated return loss characteristics of the optimized antenna show that it satisfies the requirement of 2.4/5.8 GHz WLAN and 3.5 GHz WiMAX antenna applications. Moreover, there is good agreement between the measured and simulated result in terms of radiation pattern and gain.Engineering and Physical Science Research Council through Grant EP/E022936A

Dual Segment S-Shaped Aperture-Coupled Cylindrical Dielectric Resonator Antenna for X-Band Applications.

yesA new low-cost dual-segmented dielectric resonator (DR) antenna design is proposed for wideband applications in the X-band region. Two DRs coupled to an S-shaped slot introduce interesting features. The antenna performance was characterized in terms of the reflection coefficient, gain, and radiation pattern, and detailed simulation studies indicate excellent antenna performance from 7.66 GHz to 11.2 GHz (37.5% fractional bandwidth) with a maximum gain of 6.0 dBi at 10.6 GHz while the fabricated prototype has a matched bandwidth from 7.8 GHz to 11.85 GHz (41% fractional bandwidth) and maximum gain of 6dBi. The antenna is compact, size 1 x 0.83 x 0.327 time the wavelength at 10 GHz. The two DR segments may be located on the same side or on opposite sides of the substrate, giving respectively improved gain or more uniform field patterns. Experimental testing of the prototype performance showed reasonable agreement with the predicted performance

Compact Dielectric Resonator Antenna with Band-Notched Characteristics for Ultra-Wideband Applications.

yesIn this paper, a compact dielectric resonator antenna (DRA) with band-notched characteristics for ultra-wideband applications is presented. A comprehensive parametric study was carried out using CST Microwave Studio Suite TM 2011 to analyze and optimize the characteristics of the proposed antenna. Three shapes for the coupling slot were investigated. Simulation results show that the proposed DRA had a −10 dB impedance bandwidth of 23% from 9.97 GHz to 12.558 GHz, and a maximum gain of 7.23 dBi. The antenna had a notched band centered at 10.57 GHz, which increased the reflection coefficient by 23.5 dB, and reduced the gain by 6.12 dB. The optimized designs were verified by experimental tests on fabricated samples