Identification of Aerodynamic Sound Source in the Wake of a Rotating Circular Cylinder

In order to reduce aerodynamic noise radiated from the turbulent wake of bluff bodies, vorticity structures and flow field around a rotating circular cylinder at Reynolds numbers between 102 and 104 were numerically investigated. Vorticity structures and resultant aerodynamic noise is strongly dependant on the velocity ratio, which is defined as flow velocity over rotational speed to the cylinder. At low velocity ratio, the noise level and aerodynamic forces increase and an anti-symmetric vorticity structure is observed. On the other hand, the absolute value of lift-drag ratio becomes small and alternative vorticity structure disappears as the velocity ratio exceeds about 2. As a result, the fluctuating aerodynamic forces become weak and the resulting aerodynamic sound becomes small. The noise level of the rotational cylinder is 10 dB lower than that of the conventional circular cylinder. Source terms of aerodynamic sound were also visualized by using vortex sound theory. The intensity of the source term of the separated shear layer rapidly change as the shear layers roll up. Therefore, the separated shear layers play an important role in generating aerodynamic sound at low velocity ratio. Since the anti-symmetric vorticity structure disappears at high velocity ratio, vorticity fluctuation and resultant aerodynamic noise is restrained. As a result, very interestingly, in the case of the high velocity ratio the intensity of the source term generated by the separated shear layer is maintained, however, the noise level gradually decreases. This reveals that cylinder rotation is an effective method for reducing the aerodynamic noise radiated from a turbulent wake

HEALTH AND SAFETY REGULATION OF SMALL, HIGH-RISK SUBPOPULATIONS

The choice of decision framework used to set regulatory tolerance levels for hazardous substances can be divided into rigid and flexible tolerance levels. Rigid decision frameworks include zero or deminimis that fix risk levels for some subpopulation. and/or highly tolerances The accelerating identification of highly sensitive exposed individuals and the division of the population into ever smaller subpopulations at higher risk could prove to be tremendously burdensome on regulatory systems, particularly for rigid decision frameworks. Rigid tolerance levels, philosophically based on "rights" to zero or arbitrarily low excess risks for individuals, do not contain sufficient flexibility to account for small high-risk subpopulations. Furthermore, the equal protection for all such groups is an illusion, mainly because of the potentially large number of such subgroups and the relatively fixed regulatory resources. Thus, deminimis regulation is seen as a minimal but inadequate improvement over zero risk regulation. with improved measures of the heterogeneous demand for risk reduction by various high-risk subpopulations, augmented cost-benefit analyses leading to flexible tolEr2.nces could provide a richer analytic framework for more efficient regulatory decisions. Additionally, it may be useful to attempt to c2.tegorize hazards and subpopulations on the basis of the ability to self-protect.De minimis, sensitive, decision framework, cost benefit, Food Consumption/Nutrition/Food Safety, Health Economics and Policy,

Separating weak lensing and intrinsic alignments using radio observations

We discuss methods for performing weak lensing using radio observations to recover information about the intrinsic structural properties of the source galaxies. Radio surveys provide unique information that can benefit weak lensing studies, such as HI emission, which may be used to construct galaxy velocity maps, and polarized synchrotron radiation; both of which provide information about the unlensed galaxy and can be used to reduce galaxy shape noise and the contribution of intrinsic alignments. Using a proxy for the intrinsic position angle of an observed galaxy, we develop techniques for cleanly separating weak gravitational lensing signals from intrinsic alignment contamination in forthcoming radio surveys. Random errors on the intrinsic orientation estimates introduce biases into the shear and intrinsic alignment estimates. However, we show that these biases can be corrected for if the error distribution is accurately known. We demonstrate our methods using simulations, where we reconstruct the shear and intrinsic alignment auto and cross-power spectra in three overlapping redshift bins. We find that the intrinsic position angle information can be used to successfully reconstruct both the lensing and intrinsic alignment power spectra with negligible residual bias.Comment: 17 pages, 10 figures, submitted to MNRA

A late-accelerating universe with no dark energy - and a finite-temperature big bang

Brane-world models offer the possibility of explaining the late acceleration of the universe via infra-red modifications to General Relativity, rather than a dark energy field. However, one also expects ultra-violet modifications to General Relativity, when high-energy stringy effects in the early universe begin to grow. We generalize the DGP brane-world model via an ultra-violet modification, in the form of a Gauss-Bonnet term in the bulk action. The combination of infra-red and ultra-violet modifications produces an intriguing cosmology. The DGP feature of late-time acceleration without dark energy is preserved, but there is an entirely new feature - there is no hot big bang in the early universe. The universe starts with finite density and pressure, from a "sudden" curvature singularity.Comment: revised title and minor improvements, additional references; to appear JCA

Assessing U.S. energy policy

No description supplie

A new map-making algorithm for CMB polarisation experiments

With the temperature power spectrum of the cosmic microwave background (CMB) at least four orders of magnitude larger than the B-mode polarisation power spectrum, any instrumental imperfections that couple temperature to polarisation must be carefully controlled and/or removed. Here we present two new map-making algorithms that can create polarisation maps that are clean of temperature-to-polarisation leakage systematics due to differential gain and pointing between a detector pair. Where a half wave plate is used, we show that the spin-2 systematic due to differential ellipticity can also by removed using our algorithms. The algorithms require no prior knowledge of the imperfections or temperature sky to remove the temperature leakage. Instead, they calculate the systematic and polarisation maps in one step directly from the time ordered data (TOD). The first algorithm is designed to work with scan strategies that have a good range of crossing angles for each map pixel and the second for scan strategies that have a limited range of crossing angles. The first algorithm can also be used to identify if systematic errors that have a particular spin are present in a TOD. We demonstrate the use of both algorithms and the ability to identify systematics with simulations of TOD with realistic scan strategies and instrumental noise.Comment: 11 pages, 6 figure

Crude awakening: behind the surge in oil prices

The first few months of 2008 saw crude oil prices breach one barrier after another. They topped $100 a barrel for the first time on Feb. 19, then rose past$103.76 about two weeks later, surpassing the previous inflation-adjusted peak, established in 1980. In April and early May, oil prices pushed past $110 and then$120 a barrel and beyond. ; These milestones reflect a new era in oil markets. After the tumult of the early 1980s, prices remained relatively tame for two decades - in both real and nominal terms. This long stretch of stability ended in 2004, when oil topped $40 a barrel for the first time, then embarked on a steep climb that continued into this year. ; Modern economies run on oil, so it's important to understand how recent years - with their surging prices - differ from the preceding two decades. A good starting point is strong demand, which has pushed world oil markets close to capacity. New supplies haven't kept up with this demand, fueling expectations that oil markets will remain tight for the foreseeable future. A weakening dollar has put upward pressure on the price of a commodity that trades in the U.S. currency. And because a large share of oil production takes place in politically unstable regions, fears of supply disruptions loom over markets. ; These factors have fed the steady, sometimes swift rise of oil prices in recent years. Their persistence suggests the days of relatively cheap oil are over and the global economy faces a future of high energy prices. How they play out will shape oil markets - and determine prices - for years to come.Petroleum products - Prices ; Petroleum industry and trade ; Organization of Petroleum Exporting Countries ; Dollar, American

Brane world cosmology with Gauss-Bonnet and induced gravity terms

In this thesis we investigate certain cosmological brane world models of the Randall-Sundrum type. The models are motivated by string theory but we focus on the phenomenology of the cosmology. Two models of specific interest are the Dvali-Gabadadze-Porrati (DGP, induced-gravity) model, where the brane action is modified, and the Gauss-Bonnet model where the bulk action is modified. Both of these modifications maybe motivated by string theory. We provide a brief review of Randall-Sundrum models and then consider the Kaluza-Klein modes on Minkowski and de Sitter branes, in both the two and one brane cases. The spectrum obtained for the de Sitter branes is a new result. We then consider a Friedmann-Robertson-Walker brane in order to investigate the cosmological dynamics on the brane. We present a brief discussion of the DGP and Gauss-Bonnet brane worlds. We then investigate the Gauss-Bonnet-Induced-Gravity (GBIG) model where the Gauss-Bonnet (GB) bulk term is combined with the induced-gravity (IG) brane term of the DGP model. We present a thorough investigation of cosmological dynamics, in particular focusing on GBIG models that behave like self-accelerating DGP models at late times but at early times show the remarkable feature of a finite-temperature Big Bang. We also discuss the constraints from observations, including ages and Big Bang nucleosynthesis.Comment: PhD Thesis, 104 pages, 44 figures. Contains material first presented in gr-qc/0508116 and gr-qc/060205

Circumferentially-segmented collector usable with a TWT

A TWT collector has axially-positioned collector stages in which at least one of the stages includes a plurality of annularly-arranged stage segments. The collector enhances electron beam velocity sorting by facilitating a combination of (a) selecting axial electric field distributions with application of selected voltages to the axially-positioned collector stages and (b) selecting radial electric field distributions with application of selected voltages to the annularly-arranged stage segments