Methods for estimation of Bullen turbulence spectrum parameters

Maximum likelihood and constrained least-squares methods are extended to Bullen transverse and longitudinal spectra and autocorrelation functions

Quantum Lie algebras; their existence, uniqueness and qq-antisymmetry

Quantum Lie algebras are generalizations of Lie algebras which have the quantum parameter h built into their structure. They have been defined concretely as certain submodules of the quantized enveloping algebras. On them the quantum Lie bracket is given by the quantum adjoint action. Here we define for any finite-dimensional simple complex Lie algebra g an abstract quantum Lie algebra g_h independent of any concrete realization. Its h-dependent structure constants are given in terms of inverse quantum Clebsch-Gordan coefficients. We then show that all concrete quantum Lie algebras are isomorphic to an abstract quantum Lie algebra g_h. In this way we prove two important properties of quantum Lie algebras: 1) all quantum Lie algebras associated to the same g are isomorphic, 2) the quantum Lie bracket of any quantum Lie algebra is $q$-antisymmetric. We also describe a construction of quantum Lie algebras which establishes their existence.Comment: 18 pages, amslatex. Files also available from http://www.mth.kcl.ac.uk/~delius/q-lie/qlie_biblio/qlieuniq.htm

Statistics of some atmospheric turbulence records relevant to aircraft response calculations

Methods for characterizing atmospheric turbulence are described. The methods illustrated include maximum likelihood estimation of the integral scale and intensity of records obeying the von Karman transverse power spectral form, constrained least-squares estimation of the parameters of a parametric representation of autocorrelation functions, estimation of the power spectra density of the instantaneous variance of a record with temporally fluctuating variance, and estimation of the probability density functions of various turbulence components. Descriptions of the computer programs used in the computations are given, and a full listing of these programs is included

A geometric approach to three-dimensional hipped bipedal robotic walking

This paper presents a control law that results in stable walking for a three-dimensional bipedal robot with a hip. To obtain this control law, we utilize techniques from geometric reduction, and specifically a variant of Routhian reduction termed functional Routhian reduction, to effectively decouple the dynamics of the three-dimensional biped into its sagittal and lateral components. Motivated by the decoupling afforded by functional Routhian reduction, the control law we present is obtained by combining three separate control laws: the first shapes the potential energy of the sagittal dynamics of the biped to obtain stable walking gaits when it is constrained to the sagittal plane, the second shapes the total energy of the walker so that functional Routhian reduction can be applied to decoupling the dynamics of the walker for certain initial conditions, and the third utilizes an output zeroing controller to stabilize to the surface defining these initial conditions. We numerically verify that this method results in stable walking, and we discuss certain attributes of this walking gait

Water resources development in Africa: a review and synthesis of issues, potentials, and strategies for the future

This paper analyzes how water resources development and water policy reform can be deployed to address the twin problems of food insecurity and water scarcity in Africa and, in particular, Sub-Saharan Africa. The paper reviews the current status of water supply and demand, and the existing and potential irrigated land base in Africa; reviews the performance of existing irrigation systems and assesses the magnitude of the potential contribution and cost-effectiveness of new irrigation development to future food production in Africa; and explores the potential for water conservation through demand management. Meeting the challenges of food security and water scarcity in Africa will require both selective development and exploitation of new water supplies and comprehensive policy reform that encourages efficient use of existing supplies. The most significant reforms will involve changing the institutional and legal environment in which water is supplied to one that empowers water users to make their own decisions regarding the resource. Irrigation development will not be the main source of food production growth in Africa, but increased investment in irrigation could have an important role in reducing projected cereal import demands. Rehabilitation and improvement of existing irrigation systems can be an attractive option, but projects must be selected carefully.Water conservation., Water resources development Management., Water supply., Food security., Irrigation Management Research.,

Sources of Business Cycle Fluctuations

What shocks account for the business cycle frequency and long run movements of output and prices? This paper addresses this question using the identifying assumption that only supply shocks, such as shocks to technology, oil prices, and labor supply affect output in the long run. Real and monetary aggregate demand shocks can affect output, but only in the short run. This assumption sufficiently restricts the reduced form of key macroeconomic variables to allow estimation of the shocks and their effect on output and price at all frequencies. Aggregate demand shocks account for about twenty to thirty percent of output fluctuations at business cycle frequencies. Technological shocks account for about one-quarter of cyclical fluctuations, and about one-third of output's variance at low frequencies. Shocks to oil prices are important in explaining episodes in the 1970's and 1980's. Shocks that permanently affect labor input account for the balance of fluctuations in output, namely, about half of its variance at all frequencies.

International payments imbalances of the East Asian developing economies

East Asia ; Developing countries ; Economic policy ; Balance of payments ; Balance of trade ; Econometric models

Susceptibility of White Spruce Seed Sources to Yellowheaded Spruce Sawfly, \u3ci\u3ePikonema Alaskensis,\u3c/i\u3e(Hymenoptera: Tenthredinidae)

A field caging technique was used to test the susceptibility of 25 white spruce, Picea glauca (Moench) Voss, seed sources to attack by Pikonema alaskensis (Rohwer). No sig- nificant differences were found in the number of eggs laid, number of dessicated eggs, or number of egg slits. Percent oviposition differed significantly within a tree, the south side having more eggs. Bud size differed significantly within trees and between trees but not between seed sources. The number of sawfly eggs laid on a bud could not be related to bud size. There was no significant difference in susceptibility of the seed sources studied to Pikonema alaskensis