A study of adjustment of immigrant children in a London school

The dramatic increase in the number of immigrant children in British schools during the last decade has posed many difficult problems. For both educationists and social scientists interested in the problems of culture conflict and resocialization, it presents a a real, urgent but immensely interesting issue to be studied. The research in the field to date has been almost entirely of a qualitative nature and quantitative studies are almost non-existent. The present study was undertaken to compare the socio-personal adjustment of immigrant children in a North London school, with a control group of English children, and to study the correlates of ‘adjustment’. A ‘well-adjusted’ person was defined as an individual who is (a) socially acceptable, (b) personally satisfied, (c) free from anxiety, and (d) has an objective self-concept. The variables for the study of their relationship with ‘adjustment’ were chosen partly as a result or the survey of previous studies and partly through a survey of the opinions of teachers of immigrant children. The investigator spent about eighteen months in the school as a schoolteacher for the purpose of establishing rapport. No formal testing of any kind was carried out until the investigator had established rapport with children of all races and was being perceived and categorised primarily as a teacher and not as a member of any particular race. The sample consisted of 174 West Indian (90 boys and 84 girls) and 76 Cypriot (38 boys and girls each) children at the school. This comprised the entire immigrant population at that school, with the exception of three Cypriots who could not speak English and hence could not be tested, and a few children of other races whose number was too small for any statistical analysis. A specially constructed adjustment scale (composed of four sub-scales - social acceptability, personal satisfaction, freedom from anxiety and objectivity of self-concept,) Raven Progressive Matrices, Mill Hill Vocabulary Scale, New Junior Maudsley Personality Inventory, Cotswold Personality Inventory, a semi-structured interview, and school records were used as measuring instruments. English children were found to be better adjusted, more personally satisfied, less anxious, less extraverted, less interested in things but more interested in ideas than immigrant children. Immigrant children were found to have a less objective self-concept, lower academic achievement, lower attainment in written English, vocabulary and fluency of spoken English, and lower non-verbal intelligence test scores than English children. No significant differences were found between social acceptability, non-academic achievement, interest in people and attitude towards school scores of English and Cypriot children. West Indian children were more interested in people, had a less unfavourable attitude towards school, a higher non-academic achievement, but were less socially acceptable than the English children. The Cypriots were found to be better adjusted, more socially acceptable, less anxious and as having more objective self-concept but lower non-academic achievement and less interested in people than the West Indians. No significant differences were found between the personal satisfaction, academic achievement, attainment in written English, vocabulary and fluency of spoken English, I.Q., extraversion, interest in things and ideas, and attitude towards school scores of the two groups of immigrant children. 'Adjustment' of immigrant children was found to be positively and significantly related to their academic achievement, attainment in written English, extraversion, interest in people, attitude towards school, and friendship with English children. Family size, interest in things, interest in ideas, and difference between vocational aspirations and expectations were found to be negatively and significantly related to 'adjustment', No relationship between 'adjustment' of immigrant children and age, age at the time of emigration, length of residence in the U.K., intention of returning home, living with one or both parents, working mother, non-academic achievement, fluency of spoken English, vocabulary, intelligence test scores, expectation of high status jobs, and aspiration of high status jobs, could be established. The results showed that there was very little mixing among children of different races. Only 22.4% of the West Indians claimed the friendship of even one English child while only 14.5% of the Cypriots and 2.9% of the West Indians claimed an English child as their ‘best friend’. Only 13.2% of the Cypriot and 2.9% of the West Indian families were on visiting terms with an English family in their neighbourhood. Case histories of five most 'well-adjusted' and five least ‘well-adjusted’ Cypriot and West Indian children each were recorded. Some suggestion were made about the suitable actions that could be taken by the various people concerned with the education of immigrants and some proposals for further research in the area were outlined

The non-coplanar baselines effect in radio interferometry: The W-Projection algorithm

We consider a troublesome form of non-isoplanatism in synthesis radio telescopes: non-coplanar baselines. We present a novel interpretation of the non-coplanar baselines effect as being due to differential Fresnel diffraction in the neighborhood of the array antennas. We have developed a new algorithm to deal with this effect. Our new algorithm, which we call "W-projection", has markedly superior performance compared to existing algorithms. At roughly equivalent levels of accuracy, W-projection can be up to an order of magnitude faster than the corresponding facet-based algorithms. Furthermore, the precision of result is not tightly coupled to computing time. W-projection has important consequences for the design and operation of the new generation of radio telescopes operating at centimeter and longer wavelengths.Comment: Accepted for publication in "IEEE Journal of Selected Topics in Signal Processing

Energy Sharing for Multiple Sensor Nodes with Finite Buffers

We consider the problem of finding optimal energy sharing policies that maximize the network performance of a system comprising of multiple sensor nodes and a single energy harvesting (EH) source. Sensor nodes periodically sense the random field and generate data, which is stored in the corresponding data queues. The EH source harnesses energy from ambient energy sources and the generated energy is stored in an energy buffer. Sensor nodes receive energy for data transmission from the EH source. The EH source has to efficiently share the stored energy among the nodes in order to minimize the long-run average delay in data transmission. We formulate the problem of energy sharing between the nodes in the framework of average cost infinite-horizon Markov decision processes (MDPs). We develop efficient energy sharing algorithms, namely Q-learning algorithm with exploration mechanisms based on the $\epsilon$-greedy method as well as upper confidence bound (UCB). We extend these algorithms by incorporating state and action space aggregation to tackle state-action space explosion in the MDP. We also develop a cross entropy based method that incorporates policy parameterization in order to find near optimal energy sharing policies. Through simulations, we show that our algorithms yield energy sharing policies that outperform the heuristic greedy method.Comment: 38 pages, 10 figure

Polynomials that Sign Represent Parity and Descartes' Rule of Signs

A real polynomial $P(X_1,..., X_n)$ sign represents $f: A^n \to \{0,1\}$ if for every $(a_1, ..., a_n) \in A^n$, the sign of $P(a_1,...,a_n)$ equals $(-1)^{f(a_1,...,a_n)}$. Such sign representations are well-studied in computer science and have applications to computational complexity and computational learning theory. In this work, we present a systematic study of tradeoffs between degree and sparsity of sign representations through the lens of the parity function. We attempt to prove bounds that hold for any choice of set $A$. We show that sign representing parity over $\{0,...,m-1\}^n$ with the degree in each variable at most $m-1$ requires sparsity at least $m^n$. We show that a tradeoff exists between sparsity and degree, by exhibiting a sign representation that has higher degree but lower sparsity. We show a lower bound of $n(m -2) + 1$ on the sparsity of polynomials of any degree representing parity over $\{0,..., m-1\}^n$. We prove exact bounds on the sparsity of such polynomials for any two element subset $A$. The main tool used is Descartes' Rule of Signs, a classical result in algebra, relating the sparsity of a polynomial to its number of real roots. As an application, we use bounds on sparsity to derive circuit lower bounds for depth-two AND-OR-NOT circuits with a Threshold Gate at the top. We use this to give a simple proof that such circuits need size $1.5^n$ to compute parity, which improves the previous bound of ${4/3}^{n/2}$ due to Goldmann (1997). We show a tight lower bound of $2^n$ for the inner product function over $\{0,1\}^n \times \{0, 1\}^n$.Comment: To appear in Computational Complexit

Advances in Calibration and Imaging Techniques in Radio Interferometry

This paper summarizes some of the major calibration and image reconstruction techniques used in radio interferometry and describes them in a common mathematical framework. The use of this framework has a number of benefits, ranging from clarification of the fundamentals, use of standard numerical optimization techniques, and generalization or specialization to new algorithms