Аналитическое описание поверхностей зубьев эволютных передач

Зниження габаритів зубчастих передач є актуальною задачею сучасного машинобудування. Перспективний шлях її розв'язання – застосування еволютних передач із опукло-увігнутим контактом зубців. Отримані рівняння профілів еволютних зубців на основі методу профільних нормалей. Вони необхідні для подальших досліджень якісних показників та міцності еволютних зачеплень.Lowering of dimensions of gears is an actual task of a modern machine industry. The perspective way of its decision is application of evolute gears with the convax-concave contact. On the basis of method of type normal the equations of evolute teeth are got. They are needed for further researches of high-quality indexes and durability of evolute gearings

The determinants of urban household poverty in Malaysia

Since independence in 1950s Malaysia has been recognised as one of the more successful countries in fighting poverty: head count ratio came down to 5.7 percent by 2004. However the recent process of rapid urbanization has led to an increase of urban poverty aggravated further by the 1997 Asian financial crisis. It is important to understand the nature and scale of urbanization, the various driving forces that affect it and the determinants of urban poverty as linked to this process. Our paper identifies the determinants of urban poverty in Malaysia using a logistic regression. Multiple regression model which used to be the main tool of analysis in this kind of studies has been criticised for a number of drawbacks and binary probit or logit models have been proposed as alternative and widely used. Previous studies have used income to identify poor households. We have two problems with this procedure. First, the official poverty line in Malaysia is an consumption expenditure. Secondly data on household incomes are known to be less reliable than consumption data obtained from household expenditure surveys. We therefore compare a person’s consumption expenditure with the poverty line to determine its poverty status. This agrees with the idea that poverty is the inability to attain a critical minimum amount of consumption. We study the effect of human capital, region of residence and other household characteristics on urban poverty using this benchmark A sample of 2,403 urban households from the 2004-05 Household Expenditure Survey (HES) has been used in this research. We first estimate the probability of households with specified characteristics to fall below Malaysia’s official poverty line. Results show that human capital significantly reduces the chance of being poor while migrant workers are more prone to poverty. Household size, race and regions are also important determinants of poverty outcome in urban Malaysia. Then we analyse the sensitivity of the probability estimates to shift of the poverty line over a reasonable range. Effects of education, number of children, number of male adults, number of elderly, foreign migrant-headed household, Chinese household and households living in Region 1 on poverty are robust over the shifts. The findings have important policy implications for Malaysian government which has pledged to reduce overall poverty rate to 2.8 percent and eradicate hardcore poverty by 2010 under the Ninth Malaysian Plan

Hyperextended Scalar-Tensor Gravity

We study a general Scalar-Tensor Theory with an arbitrary coupling funtion $\omega (\phi )$ but also an arbitrary dependence of the ``gravitational constant'' $G(\phi )$ in the cases in which either one of them, or both, do not admit an analytical inverse, as in the hyperextended inflationary scenario. We present the full set of field equations and study their cosmological behavior. We show that different scalar-tensor theories can be grouped in classes with the same solution for the scalar field.Comment: latex file, To appear in Physical Review

Some exact non-vacuum Bianchi VI0 and VII0 instantons

We report some new exact instantons in general relativity. These solutions are K\"ahler and fall into the symmetry classes of Bianchi types VI0 and VII0, with matter content of a stiff fluid. The qualitative behaviour of the solutions is presented, and we compare it to the known results of the corresponding self-dual Bianchi solutions. We also give axisymmetric Bianchi VII0 solutions with an electromagnetic field.Comment: latex, 15 pages with 3 eps figure

Complexity reduction of astrochemical networks

We present a new computational scheme aimed at reducing the complexity of the chemical networks in astrophysical models, one which is shown to markedly improve their computational efficiency. It contains a flux-reduction scheme that permits to deal with both large and small systems. This procedure is shown to yield a large speed-up of the corresponding numerical codes and provides good accord with the full network results. We analyse and discuss two examples involving chemistry networks of the interstellar medium and show that the results from the present reduction technique reproduce very well the results from fuller calculations.Comment: 9 pages, 7 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journa