Longitudinal control effectiveness and entry dynamics of a single-stage-to-orbit vehicle

The classical theory of flight dynamics for airplane longitudinal stability and control analysis was extended to the case of a hypervelocity reentry vehicle. This includes the elements inherent in supersonic and hypersonic flight such as the influence of the Mach number on aerodynamic characteristics, and the effect of the reaction control system and aerodynamic controls on the trim condition through a wide range of speed. Phugoid motion and angle of attack oscillation for typical cases of cruising flight, ballistic entry, and glide entry are investigated. In each case, closed form solutions for the variations in altitude, flight path angle, speed and angle of attack are obtained. The solutions explicitly display the influence of different regions design parameters and trajectory variables on the stability of the motion

Twisted and Nontwisted Bifurcations Induced by Diffusion

We discuss a diffusively perturbed predator-prey system. Freedman and Wolkowicz showed that the corresponding ODE can have a periodic solution that bifurcates from a homoclinic loop. When the diffusion coefficients are large, this solution represents a stable, spatially homogeneous time-periodic solution of the PDE. We show that when the diffusion coefficients become small, the spatially homogeneous periodic solution becomes unstable and bifurcates into spatially nonhomogeneous periodic solutions. The nature of the bifurcation is determined by the twistedness of an equilibrium/homoclinic bifurcation that occurs as the diffusion coefficients decrease. In the nontwisted case two spatially nonhomogeneous simple periodic solutions of equal period are generated, while in the twisted case a unique spatially nonhomogeneous double periodic solution is generated through period-doubling. Key Words: Reaction-diffusion equations; predator-prey systems; homoclinic bifurcations; periodic solutions.Comment: 42 pages in a tar.gz file. Use ``latex2e twisted.tex'' on the tex files. Hard copy of figures available on request from [email protected]

Foreign Direct Investment, Real Effective Exchange Rate and China’s Economy

Changes in China’s Balance of Payment (BOP) reveal that integration between China and the outside world is much closer. On the basis of these BOP changes, this paper examines Foreign Direct Investment (FDI) and Real Effective Exchange Rate (REER) in China because of their importance in economic growth. A number of important issues that may underlay China’s economy imbalance are discussed, and it is suggested that current account surpluses and FDI remain important contributors to the foreign exchange reserve accumulation. Using empirical methodology analysis, the relationships and interactions between FDI, REER and Gross Domestic Product (GDP) in China in the long-run is shown, which yield additional information about implications for the behaviors of REER and FDI in the Chinese economy

On the IMF in a Triggered Star Formation Context

The origin of the stellar initial mass function (IMF) is a fundamental issue in the theory of star formation. It is generally fit with a composite power law. Some clues on the progenitors can be found in dense starless cores that have a core mass function (CMF) with a similar shape. In the low-mass end, these mass functions increase with mass, albeit the sample may be somewhat incomplete; in the high-mass end, the mass functions decrease with mass. There is an offset in the turn-over mass between the two mass distributions. The stellar mass for the IMF peak is lower than the corresponding core mass for the CMF peak in the Pipe Nebula by about a factor of three. Smaller offsets are found between the IMF and the CMFs in other nebulae. We suggest that the offset is likely induced during a starburst episode of global star formation which is triggered by the formation of a few O/B stars in the multi-phase media, which naturally emerged through the onset of thermal instability in the cloud-core formation process. We consider the scenario that the ignition of a few massive stars photoionizes the warm medium between the cores, increases the external pressure, reduces their Bonnor?Ebert mass, and triggers the collapse of some previously stable cores. We quantitatively reproduce the IMF in the low-mass end with the assumption of additional rotational fragmentation.Comment: 3 figure

Measurements of quasi-particle tunneling in the nu = 5/2 fractional quantum Hall state

Some models of the 5/2 fractional quantum Hall state predict that the quasi-particles, which carry the charge, have non-Abelian statistics: exchange of two quasi-particles changes the wave function more dramatically than just the usual change of phase factor. Such non-Abelian statistics would make the system less sensitive to decoherence, making it a candidate for implementation of topological quantum computation. We measure quasi-particle tunneling as a function of temperature and DC bias between counter-propagating edge states. Fits to theory give e*, the quasi-particle effective charge, close to the expected value of e/4 and g, the strength of the interaction between quasi-particles, close to 3/8. Fits corresponding to the various proposed wave functions, along with qualitative features of the data, strongly favor the Abelian 331 state

Bose-Einstein supersolid phase for a novel type of momentum dependent interaction

A novel class of non-local interactions between bosons is found to favor a crystalline Bose-Einstein condensation ground state. By using both low energy effective field theory and variational wavefunction method, we compare this state not only with the homogeneous superfluid, as has been done previously, but also with the normal (non-superfluid) crystalline phase and obtain the phase diagram. The key characters are: the interaction potential displays a negative minimum at finite momentum which determines the wavevector of this supersolid phase; and the wavelength corresponding to the momentum minimum needs to be greater than the mean inter-boson distance.Comment: 4 pages 3 figures, fig 1 and fig 2 update

Motor entry point acupuncture for shoulder abduction dysfunction after stroke: a randomized controlled feasibility trial

Introduction: Evidence has suggested that shoulder abduction dysfunction after stroke can be treated with acupuncture, but it remains unclear which acupuncture approach may be more effective. This trial compared two different acupuncture interventions (Motor Entry Point acupuncture (MEPA) and Standard acupuncture (SA) for patients experiencing post-stroke shoulder abduction dysfunction. Methods: Hospital in-patients with post-stroke shoulder abduction dysfunction of two weeks duration and who agreed to participate in the trial were randomized into two groups. The SA group received acupuncture treatment at LI15, LI14, LI11, LI10 and LI4 (n=20); the MEPA group received acupuncture at the mid-third of deltoid (n=20). Each group received acupuncture for 40 minutes, 6 times a week for 4 weeks. Outcomes were the range of motion (ROM) and the manual muscle test (MMT). Results: Forty in-patients (19 women, 21 men; age range: 35-75 years) were enrolled in this trial. There was significant improvement in shoulder abduction dysfunction in both groups after 4 weeks of treatment (P＜0.05). The MEPA group reported larger ROM and improved MMT compared to the SA group (P＜0.05) and the recovery of muscle strength in MEPA group was superior to the SA group (P＜0.05). Conclusion: Compared to SA therapy, MEPA therapy may be more effective for treating physical functional disability in post-stroke patients

Numerical Simulation of Free-fountains in a Homogeneous Fluid

The behaviour of plane fountains, resulting from the injection of dense fluid upwards into a large container of homogeneous fluid of lower density, is investigated. The transient behaviour of fountains with parabolic inlet velocity profile and Reynolds numbers, 50 ≤ Re ≤ 150, Prandtl numbers, Pr=7, 300 and 700, and Froude numbers, Fr = 0.25 to 10.0 are studied numerically. The fountain behaviour falls into three distinct regimes; steady and symmetric; unsteady and periodic flapping; unsteady and aperiodic. The analytical scaling of nondimensional fountain height, zm, with Fr and Re is zm ∼ Fr4/3−2γ/3Re−γ. The constant γ is found empirically for each of the regimes. The fountain height decreases with increase in Reynolds number in the steady region but increases with Reynolds number in the unsteady regimes. However, the fountain height increases with Froude number in all regimes. Numerical results and the analytical scaling show that zm is independent of Prandtl number in the range considered. The fountain exhibits periodic lateral oscillations, i.e., periodic flapping for intermediate Froude numbers ranging from 1.25 ≤ Fr ≤ 2.25