Dynamic simulation of task constrained of a rigid-flexible manipulator

A rigid-flexible manipulator may be assigned tasks in a moving environment where the winds or vibrations affect the position and/or orientation of surface of operation. Consequently, losses of the contact and perhaps degradation of the performance may occur as references are changed. When the environment is moving, knowledge of the angle α between the contact surface and the horizontal is required at every instant. In this paper, different profiles for the time varying angle α are proposed to investigate the effect of this change into the contact force and the joint torques of a rigid-flexible manipulator. The coefficients of the equation of the proposed rotating surface are changing with time to determine the new X and Y coordinates of the moving surface as the surface rotates

Finding Young Stellar Populations in Elliptical Galaxies from Independent Components of Optical Spectra

Elliptical galaxies are believed to consist of a single population of old stars formed together at an early epoch in the Universe, yet recent analyses of galaxy spectra seem to indicate the presence of significant younger populations of stars in them. The detailed physical modelling of such populations is computationally expensive, inhibiting the detailed analysis of the several million galaxy spectra becoming available over the next few years. Here we present a data mining application aimed at decomposing the spectra of elliptical galaxies into several coeval stellar populations, without the use of detailed physical models. This is achieved by performing a linear independent basis transformation that essentially decouples the initial problem of joint processing of a set of correlated spectral measurements into that of the independent processing of a small set of prototypical spectra. Two methods are investigated: (1) A fast projection approach is derived by exploiting the correlation structure of neighboring wavelength bins within the spectral data. (2) A factorisation method that takes advantage of the positivity of the spectra is also investigated. The preliminary results show that typical features observed in stellar population spectra of different evolutionary histories can be convincingly disentangled by these methods, despite the absence of input physics. The success of this basis transformation analysis in recovering physically interpretable representations indicates that this technique is a potentially powerful tool for astronomical data mining.Comment: 12 Pages, 7 figures; accepted in SIAM 2005 International Conference on Data Mining, Newport Beach, CA, April 200

Drift rate control of a Brownian processing system

A system manager dynamically controls a diffusion process Z that lives in a finite interval [0,b]. Control takes the form of a negative drift rate \theta that is chosen from a fixed set A of available values. The controlled process evolves according to the differential relationship dZ=dX-\theta(Z) dt+dL-dU, where X is a (0,\sigma) Brownian motion, and L and U are increasing processes that enforce a lower reflecting barrier at Z=0 and an upper reflecting barrier at Z=b, respectively. The cumulative cost process increases according to the differential relationship d\xi =c(\theta(Z)) dt+p dU, where c(\cdot) is a nondecreasing cost of control and p>0 is a penalty rate associated with displacement at the upper boundary. The objective is to minimize long-run average cost. This problem is solved explicitly, which allows one to also solve the following, essentially equivalent formulation: minimize the long-run average cost of control subject to an upper bound constraint on the average rate at which U increases. The two special problem features that allow an explicit solution are the use of a long-run average cost criterion, as opposed to a discounted cost criterion, and the lack of state-related costs other than boundary displacement penalties. The application of this theory to power control in wireless communication is discussed.Comment: Published at http://dx.doi.org/10.1214/105051604000000855 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

A comparative study of concrete properties using coconut shell and palm kernel shell as coarse aggregates

The high cost of conventional building materials is a major factor affecting housing delivery in Nigeria. This has necessitated research into alternative materials of construction. This paper presents the results of an investigation carried out on the comparative cost analysis and strength characteristics of concrete produced using crushed, granular coconut and palm kernel shells as substitutes for conventional coarse aggregate in gradation of 0%, 25%, 50%, 75% and 100%. Two mix ratios (1:1:2 and 1:2:4) were used. A total of320 cubes ofsize 100�100�100mm were cast, tested and their physical and mechanical properties determined. The results ofthe tests showed that the compressive strength ofthe concrete decreased as the percentage of the shells increased in the two mix ratios. However, concrete obtained from coconut shells exhibited a higher compressive strength than palm kernel shell concrete in the two mix proportions. The results also indicated cost reduction of 30% and 42% for concrete produced from coconut shells and palm kernel shells, respectively. Considering the strength/economy ratio, it was concluded that coconut shells were more suitable than palm kernel shells when used as substitute for conventional aggregates in concrete production. r 2005 Elsevier Ltd. All rights reserved

Studies on termite hill and lime as partial replacement for cement in plastering

This study investigated the compressive strength and water absorption capacity of 50�50�50mm mortar cubes made from mixes containing lime, termite hill and cement and sand.Two mix ratios (1:4 and 1:6) and varying binder replacements of cement with lime or termite hill amounting to 0%, 10%, 20%, 30%, 40% and 50% were used.Test results showed that the compressive strength of the mortar cubes increases with age and decreases with increasing percentage replacement of cement with lime and termite hill.However, for mix ratio 1:6, up to 20% replacement of cement with either lime or termite hill, all the mortar cubes had the same strength; subsequently, the termite hill exhibited a higher compressive strength.For mix ratio 1:4, mortar cubes made from lime/cement and termite hill/cement mixtures had the same strength at 50% replacement.Generally, water absorption is higher in mixtures containing lime (18.10% and 14.20% for mix ratios 1:6 and 1:4, respectively, both at 50% replacement level) than those containing termite hill (16.10% and 13.02% for mix ratios 1:6 and 1:4, respectively, both at 50% replacement level). Termite hills seem to be promising as a suitable, locally available housing material for plastering. r 2005 Elsevier Ltd.All rights reserved

Effect of granite dust on the performance characteristics of kernelrazzo floor finish

This study is part of an on-going research on the durability performance of kernelrazzo, a type of terrazzo floor finish. It investigated the effect of partial replacement of the coarse aggregate with granite dust on the compressive strength, water absorption capacity and density of kernelrazzo. Two mix ratios (1:3 and 1:4), varying aggregate replacements of marble chipping with burnt palm kernel shells amounting to 0%, 25%, 50%, 75% and 100%, varying percentage replacements of all coarse aggregates with granite dust amounting to 0%, 10%, 30% and 50% were used. Cost comparisons were also made. Test results showed that the compressive strength of kernelrazzo increases up to a maximum of 30% coarse aggregate replacement by granite dust for both mixes for 0–50% replacement of marble chippings with palm kernel shells. For 75–100% marble chippings replacement, the compressive strength increases with increasing amount of granite dust. The water absorption capacity and density (upto 30% of granite dust) decrease and increase, respectively, with increase in percentage of granite dust. The cost of kernelrazo decreases with increase in the percentage of replacement of coarse aggregates with granite dust, except for 100% marble chipping replacement. It was recommended that to produce a good kernelrazzo floor finish in terms of strength, durability, density, water absorption capacity and cost, the overall coarse aggregate should not contain more than 50% of palm kernel shells for 1:4 and 1:3 mix ratios with a maximum of 30% aggregate replacement with granite dust. ? 2004 Elsevier Ltd. All rights reserved

The Role of Language in the Assimilation of Lebanese Immigrants in Australia.

Most research surveys in recent years have revealed that problems of language permeate every aspect of life of migrant communities. Migrants who have attained a reasonable command of English are likely to be better adjusted and therefore more easily accepted by the host society and less vulnerable to exploitation than are other members of their community; circumstances which obviously make for easier assimilation. A methodological study was set up to investigate degrees in acquiring the varying standards of knowledge of English among Lebanese migrants, attempts made to learn English after immigration, the language spoken at home, the insistence of parents that their children learn English, and several other measurements. Specifically designed questions and a brief multidimensional test were employed to assist in the overall analysis