Implementation of uniform perturbation method for potential flow past axisymmetric and two-dimensional bodies

The aerodynamic characteristics of potential flow past an axisymmetric slender body and a thin airfoil are calculated using a uniform perturbation analysis method. The method is based on the superposition of potentials of point singularities distributed inside the body. The strength distribution satisfies a linear integral equation by enforcing the flow tangency condition on the surface of the body. The complete uniform asymptotic expansion of its solution is obtained with respect to the slenderness ratio by modifying and adapting an existing technique. Results calculated by the perturbation analysis method are compared with the existing surface singularity panel method and some available analytical solutions for a number of cases under identical conditions. From these comparisons, it is found that the perturbation analysis method can provide quite accurate results for bodies with small slenderness ratio. The present method is much simpler and requires less memory and computation time than existing surface singularity panel methods of comparable accuracy

In situ real-time analysis of alloy film composition and segregation dynamics with parallel detection reflection electron energy loss spectroscopy

Real-time measurements of GexSi1 – x/Si(001) composition and segregation dynamics in Sn/Si(001) in molecular beam epitaxy are demonstrated using parallel detection reflection electron energy loss spectroscopy. Parallel detection enables quantitative acquisition of low-loss spectra in a time of < 500 µs and surface composition determination in GexSi1 – x/Si(001) via Ge L2,3 core loss analysis to a precision of approximately 2% in time of order 1 s. Segregation and trapping kinetics of monolayer thickness Sn films during Si epitaxy on Sn-covered Si(100) has also been studied using the Sn M4.5 core loss

Rare typhoon development near the equator

In Recent Advances in Atmospheric Sciences in Asia-Pacific. (Eds: K.N. Liou, M.D. Chou and H. H. Hsu), World Scientific Publication Company, 172-181.The formation of Typhoon Vamei on 27 December 2001 in the southern South China Sea was the first-observed tropical cyclogenesis within 1.5 degrees of the equator. This rare event was first detected by observations of typhoon strength winds from a US navy ship, and the existence of an eye structure was confirmed by satellite and radar imageries. This paper reviews these observations, and discusses the dynamic theory that may explain the process suggested by Chang et al. (2003) in which a strong cold surge event interacting with the Borneo vortex led to the equatorial development. As pointed out by Chang et al., the most intriguing question is not how Vamei could form so close to the equator, but is why such a formation was not observed before then. The formation of Typhoon Vamei on 27 December 2001 in the southern South China Sea was the first-observed tropical cyclogenesis within 1.5 degrees of the equator. This rare event was first detected by observations of typhoon strength winds from a US navy ship, and the existence of an eye structure was confirmed by satellite and radar imageries. This paper reviews these observations, and discusses the dynamic theory that may explain the process suggested by Chang et al. (2003) in which a strong cold surge event interacting with the Borneo vortex led to the equatorial development. As pointed out by Chang et al., the most intriguing question is not how Vamei could form so close to the equator, but is why such a formation was not observed before then

Three‐Atom Scattering in Gas‐Phase Electron Diffraction: A Tractable Limiting Case

The contribution of intramolecular multiple scattering in electron diffraction patterns of gas molecules is investigated by Glauber's method. An analytical expression for three‐atom scattering is derived for the limiting case in which the distance between atoms is large compared with atomic radii. This expression accounts well for the discrepancies between observed and conventionally calculated scattered intensities reported by Jacob and Bartell in the case of ReF6. The analogous four‐atom scattering is found to be very small.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71249/2/JCPSA6-56-5-2364-1.pd

Three‐atom scattering in gas‐phase electron diffraction. II. A general treatment

Intramolecular multiple scattering of electrons by polyatomic gas molecules is investigated with the aid of Glauber's theory of high energy elastic scattering. The key to a simpler and more rapidly convergent expression for dynamic scattering corrections is found in a propitious transformation of variables. An analytical representation of the corrections averaged over molecular rotations and vibrations is presented in a form suitable for routine electron diffraction analyses of molecular structure. Magnitudes and practical considerations in analyses are briefly discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70806/2/JCPSA6-58-12-5654-1.pd

Molecular structure of phosphabenzene: Analysis combining electron diffraction and microwave data

The average (ra) structure of vapor phase C5H5P, the phosphorus congener of pyridine, was deduced. Vibrational corrections of diffraction data and rotational constants were made via a normal coordinate analysis based on an approximate quadratic force field. The heterocyclic molecule was found to be planar with principal structure parameters and uncertainties (2.5σ) of rg(C�P) = 1.733±0.003 Årg(C�P)=1.733±0.003Å, rg(C2�C3) = 1.413±0.010 Årg(C2�C3)=1.413±0.010Å, rg(C3�C4) = 1.384±0.012 Årg(C3�C4)=1.384±0.012Å, rg(C�H) = 1.122±0.015 Årg(C�H)=1.122±0.015Å, ∡CPC = 101.1°±0.3°∡CPC=101.1°±0.3°, ∡PCC = 124.4°±0.7°∡PCC=124.4°±0.7°, and ∡C2C3C4 = 123.7°±0.8°∡C2C3C4=123.7°±0.8°. Amplitudes of vibration were determined in the diffraction analysis as well as in the normal coordinate computation. A variety of different types of error matrices were computed to assess the effect of data correlations and the possible coupling, over and above scale factor shifts, between systematic errors in intensities and derived parameters. Conventional treatments of data correlations appear to lead to overoptimistic error estimates in the case of the longer internuclear distances. The structural characteristics of phosphabenzene are those expected for an aromatic molecule. Semiempirical molecular orbital calculations, adjusted to fit the experimental structure, suggest a small but significant involvement of phosphorus d orbitals in the π bonding.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69578/2/JCPSA6-61-7-2840-1.pd

On the dominance of J(P)=0(+) ground states in even-even nuclei from random two-body interactions

Recent calculations using random two-body interactions showed a preponderance of J(P)=0(+) ground states, despite the fact that there is no strong pairing character in the force. We carry out an analysis of a system of identical particles occupying orbits with j=1/2, 3/2 and 5/2 and discuss some general features of the spectra derived from random two-body interactions. We show that for random two-body interactions that are not time-reversal invariant the dominance of 0(+) states in this case is more pronounced, indicating that time-reversal invariance cannot be the origin of the 0(+) dominance.Comment: 8 pages, 3 tables and 3 figures. Phys. Rev. C, in pres

Patterns of antihypertensive prescribing, discontinuation and switching among a Hong Kong Chinese population from over one million prescriptions

Hypertension is an alarming public health problem among Chinese. The present study evaluated the prescribing patterns, discontinuation and switching profiles of antihypertensive agents and their associated factors in one Hong Kong Chinese population. Data were retrieved from computerized records for patients prescribed anti-hypertensive agents in government primary care clinics of Hong Kong from January, 2004 to June, 2007. A total of 1,069,836 antihypertensive drug visits, representing 67,028 patients, were analyzed. The most commonly prescribed drugs were Calcium Channel Blockers (CCBs) (49%), b-Blockers (BBs) (46%) and Angiotensin-Converting Enzyme Inhibitors (ACEIs) (19%). Thiazide diuretic prescribing was low (13%) and on the decline (14% in 2004 to 12% in 2007). Prescribing of ACEIs was rising (16% in 2004 to 23% in 2007). Patients’ age, gender, and socio-economic status were independent predictors of class of anti-hypertensive prescribed but explained less than 3.5% of the variation observed. Drug discontinuation was highest for BBs (21%) and lowest for CCBs (12%). The high rates of discontinuation in BBs remained apparent after controlling for confounding variables. Switching was less common than discontinuation and was most likely with thiazide diuretics. To summarize, prescribing of CCBs and BBs were high and that of thiazide diuretics particularly low in this Chinese population when compared with international trends. CCBs may be a particularly favorable antihypertensive treatment in Chinese, given the high discontinuation rates of BBs and international guidelines advising against the use of BBs as first-line therapy. The low use of thiazide diuretics warrants further clinical and cost effectiveness studies among Chinese