Waves in a hot uniaxial plasma excited by a current source

The fields excited by a short dipole antenna in a hot uniaxially anisotropic plasma (B_0→∞) have been studied. When ω<ω_p, the dipole effectively excites two propagating waves, a slow wave and a fast wave, inside a cone of half‐cone angle sin^(−1)(ω/ω_p). Inside the cone a characteristic interference structure in the angular distribution of the fields is noted. Outside the cone fields fall off exponentially. The appearance of the cone and the characteristic interference structure in the field is useful from the viewpoint of laboratory diagnostics

Spin-charge and spin-orbital coupling effects on spin dynamics in ferromagnetic manganites

Correlation-induced spin-charge and spin-orbital coupling effects on spin dynamics in ferromagnetic manganites are calculated with realistic parameters in order to provide a quantitative comparison with experimental results for spin stiffness, magnon dispersion, magnon damping, anomalous zone-boundary magnon softening, and Curie temperature. The role of orbital degeneracy, orbital ordering, and orbital correlations on spin dynamics in different doping regimes is highlighted.Comment: 19 pages, 9 figure

Adaptive and Supertwisting Adaptive Spacecraft Orbit Control Around Asteroids

This paper addresses the development of control systems for the orbit control of spacecraft around irregularly shaped rotating asteroids with uncertain parameters. The objective is to steer the spacecraft along prescribed orbits. First, a nonlinear adaptive law for orbit control was designed. This was followed by the design of a supertwisting adaptive (STWA) control system. In the closed-loop system, which includes the adaptive law or the STWA law, all the signals remain bounded, and the trajectory tracking error asymptotically converges to zero for any initial condition. Finally, under the assumption of boundedness of the derivative of the uncertain functions of the model in a region of the state space, a supertwisting control (STW) law for finite-time convergence of the trajectory was obtained. Based on the Lyapunov theory, stability properties of the closed-loop systems were analyzed. Simulation results for 433 Eros and Ida asteroids were presented for illustration. The results showed that control of spacecraft along closed orbits or to a fixed point is accomplished using each of these controllers, despite uncertainties in the parameters of the asteroid models

Arsenic(III) remediation from contaminated water by oxidation and Fe/Al co-precipitation

Battery grade γ-MnO2 powder was investigated as an oxidant and an adsorbent in combination with Fe/Al coagulants for removal of arsenic from contaminated water. Simultaneous oxidation of As(III) and removal by coprecipitation/adsorption (one step process) was compared with pre-oxidation and subsequent removal by coprecipitation/adsorption (two step process). The rate of As(III) oxidation with MnO2 is completed in two stages: rapid initially followed by a first order reaction. As(III) is oxidised to As(V) by the MnO2 with a release of approximately 1:1 molar Mn(II) into the solution. No significant pH effect on oxidation of As(III) was observed in the pH range 4 - 6. The rate showed a decreasing trend above pH 6. The removal of As(V) by adsorption on the MnO2 decreased significantly with increasing pH from 4 to 8. The adsorption capacity of the γ-MnO2 with particle size 90% passing 10 µm was determined to be 1.5 mg/g at pH 7. MnO2 was found to be more effective as an oxidant for As(III) in the two step process than in the one step process

Organisational change and development of reformed Chinese township and village enterprises

This article is (c) Emerald Group Publishing and permission has been granted for this version to appear here (http://bura.brunel.ac.uk/handle/2438/8263). Emerald does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from Emerald Group Publishing Limited.Purpose – This paper aims to investigate the organisational changes (OCs) and the development of Chinese reformed township and village enterprises (RTVEs), their marketing and R&D strategies, and the impact of changes in terms of overall performance. Design/methodology/approach – A case study methodology involving semi-structured interviews is adopted. The unit chosen is the Guotai International Group (GTIG) in Zhangjiagang, Suzhou, Jiangsu province, China, in which the organisational changes over a period of over 40 years are analysed. Findings – OCs in Chinese RTVEs are found to be driven by a combination of local government plans and market forces. Considering the hybrid nature of the organisation and ownership structures, changes in Chinese RTVEs follow a very much “top-down” approach. Research limitations/implications – The findings imply that managers appointed by the state in RTVEs usually lack the necessary skills in marketing and business management, and can be resistant to organisational changes, such as the willingness to undertake risks. As a result, RTVEs may become stuck in a cycle of low-cost, low-tech products, inhibiting any breakthrough in developing their own quality brands. Originality/value – This is one of few papers studying change over a long span of time to arrive at research findings that will be useful to academic researchers in their future work. The qualitative findings from this paper would also enrich the literatures on organisational change in Chinese RTVEs

Spin waves in the (0,pi) and (0,pi,pi) ordered SDW states of the t-t' Hubbard model: Application to doped iron pnictides

Spin waves in (0,pi) and (0,pi,pi) ordered spin-density-wave (SDW) states of the t-t' Hubbard model are investigated at finite doping. In the presence of small t', these composite ferro-antiferromagnetic (F-AF) states are found to be strongly stabilized at finite hole doping due to enhanced carrier-induced ferromagnetic spin couplings as in metallic ferromagnets. Anisotropic spin-wave velocities, spin-wave energy scale of around 200meV, reduced magnetic moment, and rapid suppression of magnetic order with electron doping x (corresponding to F substitution of O atoms in La O_{1-x} F_x Fe As or Ni substitution of Fe atoms in Ba Fe_{2-x} Ni_x As_2) obtained in this model are in agreement with observed magnetic properties of doped iron pnictides.Comment: 13 pages, 3 figure

High-energy magnon dispersion and multi-magnon continuum in the two-dimensional Heisenberg antiferromagnet

We use quantum Monte Carlo simulations and numerical analytic continuation to study high-energy spin excitations in the two-dimensional S=1/2 Heisenberg antiferromagnet at low temperature. We present results for both the transverse and longitudinal dynamic spin structure factor S(q,w) at q=(pi,0) and (pi/2,pi/2). Linear spin-wave theory predicts no dispersion on the line connecting these momenta. Our calculations show that in fact the magnon energy at (pi,0) is 10% lower than at (pi/2,pi/2). We also discuss the transverse and longitudinal multi-magnon continua and their relevance to neutron scattering experiments.Comment: 4 page

Approaches and possible improvements in the area of multibody dynamics modeling

A wide ranging look is taken at issues involved in the dynamic modeling of complex, multibodied orbiting space systems. Capabilities and limitations of two major codes (DISCOS, TREETOPS) are assessed and possible extensions to the CONTOPS software are outlined. In addition, recommendations are made concerning the direction future development should take in order to achieve higher fidelity, more computationally efficient multibody software solutions

Some new evidence on determinants of foreign direct investment in developing countries

The authors of this paper expand on earlier studies of the determinants of foreign direct investment (FDI) by empirically analyzing various factors - including political risk, business conditions, and macroeconomic variables - that influence direct investment flows to developing countries. They try to fill a gap in the literature by examining qualitative factors. Using a pooled model of developing countries, they test three groups of hypotheses on what influences direct investment. Tests of the first hypothesis indicate that a qualitative index of political risk is a significant determinant of FDI flows for countries that have historically attracted high FDI flows. For countries that have not attracted such flows, sociopolitical instability has a negative impact on investment flows. Tests of the second hypothesis show that a general qualitative index of business operation conditions is an important determinant of FDI in countries that receive high flows. This country group also shows a positive relationship between taxes on international transactions and FDI flows. Results from tests of the third hypothesis reveal that exports generally, especially manufacturing exports, are significant determinant of FDI flows for countries in which FDI is high. Finally, export orientation is the strongest variable for explaining why a country attracts FDI. This finding is in line with the secular trend toward increasing complementarity between trade and FDI.Labor Policies,Economic Theory&Research,Environmental Economics&Policies,Statistical&Mathematical Sciences,International Terrorism&Counterterrorism,Environmental Economics&Policies,Inequality,Statistical&Mathematical Sciences,Foreign Direct Investment,Economic Theory&Research