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This work was carried out in order to optimize the friction phase parameters, of friction welding of M2 high speed steel, to AISI 1040 medium carbon steel, namely; rotational speed, friction pressure and friction time. The experiments were designed as per Taguchi method. The optimization of the experimentally obtained results was carried out by trying three mathematical models, namely; a multiple linear regression model without interaction effect, a multiple linear regression model with interactions effect, and a second-order polynomial regression model. The three models were evaluated using the experimental data, the coefficient of multiple determination R2, and Standard error of the regression (S), were used as the evaluation criteria of the models. The polynomial model was chosen, and optimized using a Genetic Algorithm. The optimal value of the joint strength of 411 MPa was obtained at the highest value of the time ( 44.9 sec.) and the pressure of 112 MPs and the speed of 1349 r.p.m.

A subset D of the vertex set V(G) of a graph G is said to be a dominating set if every vertex not in D is adjacent to atleast one vertex in D. A dominating set D is said to be an eccentric dominating set if for every v ? V?D, there exists atleast one eccentric point of v in D. A subset D is a distance closed set of G if for each vertex u ? D and for each w ? V?D, there exists atleast one vertex v ? D such that d(u, v) = dG(u, w). An eccentric dominating set D of G is a distance closed eccentric dominating set if the induced subgraph is distance closed. The minimum of the cardinalities of the distance closed eccentric dominating set is called as the distance closed eccentric domination number ?dced(G) of G. In this paper, bounds for ?dced(G), its exact value for some particular classes of graphs and some results on distance closed eccentric domination number are obtained.

We are very happy to announce that from 21st February 2011, Dr.Chukwunonso ECC Ejike has joined the team of Elixir Editorial Advisory Board. He will carry a special responsibility for dealing with manuscripts based on the Biochemistry. Dr.Chukwunonso ECC Ejike is currently working Department of Biochemistry, Michael Okpara University of Agriculture, Umudike, PMB 7267 Umuahia, Abia State, Nigeria. The appointment of Dr.Chukwunonso ECC Ejike as member Editorial Advisory Board strengthens the links with Iran and will make it easier for prospective authors to establish contact with the journal. Please send any expressions of interest to chiefeditor@elixirjournal.org. Sincerely Editor-in-Chief

This literature review consists of three parts. In the first part, a brief introduction of speaking comprehension will be offered, followed by a discussion of the importance of speaking comprehension. Then, an overview of speaking skills will be given. Additionally, potential obstacles for students in speaking comprehension will be introduced. Last, a discussion on factors that contribute to speaking difficulties and thus affect speaking comprehension will be presented.The second part looks at defining some basic concepts and theories behind dynamic assessment (DA) such as: (a) sociocultural theory of mind, (b) zone of proximal development, (c) dynamic assessment, and (d) dynamic assessment of dynamic abilities.In the third part of this review, literature on DA is divided into the following sections: (e) components of DA, (f) models of DA, (g) approaches to DA, (h) criticism of dynamic assessment, (i) dynamic assessment and psychometric critiques, (j) previous research on DA in language education, (k) DA in the foreign language setting, (l) group dynamic assessment in the foreign language classroom, and (m) DA/GDA in Iran.

The main focus of the study was to assess the effects of determinants of financial performance on manufacturing firms. The objective of this study was to examine the determinants of financial performance of manufacturing firms in Kenya. The study examined the effect of capital structure with reference to identify the effect of equity, debentures and retained earnings on financial performance of manufacturing firms in Kenya. The research scope focused on manufacturing firms in Kenya. The target population of the study being 199 manufacturing firms in Nairobi County taken to be a representative of all manufacturing firms in Kenya. The study adopted a survey design that was both descriptive and exploratory in collecting data. The key findings were that determinants of financial performance individually had a positive influence on the financial performance of manufacturing firms. The results indicated a moderately significant linear relationship between capital structure and manufacturing firm’s performance. Managers who were consulted about these results attributed the low explanatory power of variables to stiff competition, quality of the product and government policies. The study assists policy makers in coming up with better policies on improvement of financial performance. The study adds to the literature on manufacturing firm’s financial performance.

Corcyra cephalonica, the food grain pests were exposed to Castor leaf and fruit extracts for toxicity evaluation at 24, 48, 72 and 96 hrs using percent and probit kill method(Finney-1971). The IIIrd instar larvae were exposed to the sub-lethal doses of 150, 300 and 450 mg of leaf and fruit extracts for 10 days and their total protein and carbohydrates were estimated. The Protein and Carbohydrates were found decreased followed by delayed metamorphosis and deformed adults emerged from the pupae.

Liquid 13C-NMR (Nuclear Magnetic Resonance Spectroscopy) spectra of HA (humic acid) extracted from a Hanslope Soil, Writtle College, UK under five types of land management: grassland under permanent pasture on 5 y ley before stocking; grassland under permanent pasture sown with red clover a y before stocking; grassland under permanent pasture treated with N-fertilizer a y before stocking; arable land under barley and deciduous woodland showed four major fragments: the aliphatic (alkyl C) region between 10 – 48 ppm; the carbohydrate (o-alkyl C) region between 49 and 110 ppm; the aromatic (aryl C) region between 111 and 165 ppm and the carboxyl region between 166 and 195 ppm. The study also revealed carboxyl conspicuous spectra between 150 and 200 ppm. The highest concentration of humic acid was in deciduous woodland, 55.2 mg g-1, and least in permanent pasture on a 5 y ley before stocking, 33.8 mg g-1.. Since soil organic matter (SOM) influences soil structure and fertility, humic substances effects bioavailability of elements and chemical compounds in the environment. The degradation of humic substances are slow. Hence, they do not appear to be a major direct source of nutrients – carbon, nitrogen, phosphorus and sulphur.

The present experimental study explains the effect of method of curing on the compressive strength of Pavement Concrete produced with Blended cement and non-chloride hardening Accelerator. Portland Pozzolana Cement (PPC) was used in the production of concrete mixtures. Concrete mixtures were designed as per the new guidelines of IS 10262: 2009. Accelerator dosage was varied from 2 liters to 5 liters per cubic meter of concrete in seven equal intervals. Compressive strength of standard cube specimens (150 mm) at early age and at full maturity cured with water and alternatively with wax based membrane forming curing compound, was studied. Performance of accelerator at a given age of concrete was assessed based on the maximum percentage increase in the compressive strength, measured with reference to the strength of control mixture (without accelerator) at the corresponding age. Average efficiency of the curing compound at a given age, calculated as the ratio of average compressive strength of concrete cured with it to that cured with water, was also studied. The test results revealed that the type of curing did not affect optimum performance of accelerator. Average efficiency of the curing compound was found to be more at early age than at later age.

The study examined the effect of parental conflict and divorce/separation on children’s attitude towards marriage in Nigeria. Three hundred and six undergraduate students of Adekunle Ajasin University, Akungba-Akoko in Ondo State, Nigeria were randomly selected and used for the study. Participants’ age ranges between 19 and 27 years with a mean age of 22.03 years. Three hypotheses were tested and results of analysis of data showed that parental conflict and divorce significantly affects children’s attitude towards marriage [t (304) = 13.96, p <.05]. It was also revealed that there was a significant effect of sex on attitude of undergraduate students from divorced families towards marriage [t (124) = 7.95, p<.05]. Results also indicated that children who attributed parental conflict and divorce to inability of parents to give up personal freedom were significantly different on their attitude towards marriage from those who attributed parental conflict and divorce to a lack of mutual trust, poor communication, and discontentment [F (4,270) = 13.25, p<.05]. Results were discussed in light of available literature and recommendations were made.

Abacus has been considered as one of the most significant tools used for teaching and learning of mathematics among primary school mathematics teachers since it helps in spurring better performance in mathematics. However, most of the teachers who use it have reported poor and perennial ineffective use of Abacus in Rachuonyo South Sub County. It is a simple mathematics tool used for calculation and easy to use when solving problems in mathematics. The study objectives were to; find out how the effective use of Abacus can be achieved; to determine age and gender differences in the effective use of Abacus, to explore the challenges faced by mathematics teachers in using Abacus and finally to establish the strategies that could ensure the effective use of Abacus in the teaching and learning of mathematics in public primary schools. Using descriptive survey design, this study was framed from Vygotsky’s constructivism theoretical perspective. This study targeted 170 public primary schools with 1,069 mathematics teachers of which568 were males and 501 were females. Purposive random sampling technique was used to select a sample size of 30% which was 51 public primary schools and 321 class three mathematics teachers. Questionnaires were used for quantitative data collection. Interviews were conducted among 51 heads of mathematics department while observation was done throughout the process. The validity of the instruments for data collection was ensured by expert judgment of the University lecturers. The reliability was determined by the Split Half method and a reliability coefficient of r=0.791was reported. Trustworthiness of the study ensured the validity and reliability of the data from the study. The quantitative data was analysed using descriptive statistics with the aid of Statistical Package for Social Sciences SPSS version 22 while qualitative data was analysed based on the construct items relating to important components on the use of Abacus. The study established that, Abacus improves performance in mathematics among pupils in primary schools in Kasipul Division. The findings of the study also revealed that, teachers had positive attitude towards Abacus. Abacus is good and effective in spurring new skills for teaching and learning of mathematics, however, most of the mathematics teachers lack the skills to use abacus effectively and need to be trained on the use of abacus. Age differences did not significantly affect the effectiveness in the use of Abacus in teaching mathematics; however, there was gender difference on the effective use of Abacus for teaching mathematics where effectiveness for male teachers was higher than that of their female counterparts. The study also established several challenges faced by mathematics teachers in the use of Abacus simply due to lack of skills. The study findings established that, mathematics teachers adopted several strategies to ensure effective use of Abacus in the teaching and learning of mathematics. The study recommended that, the Kenyan Ministry of Education should train the mathematics teachers on the effective use of abacus. Moreover, the Kenya Institute for Curriculum Development should infuse the use of Abacus into the mathematics syllabus. The significance of this study therefore is that, it is believed the findings of this study will be used by mathematics teachers to improve in teaching mathematics, provide curriculum planners with an insight to infuse effective use of abacus in mathematics curriculum development and finally it is hoped that this study will generate knew knowledge in this field of study and further research.