Collapse of an initially spherical vapour cavity in the neighbourhood of a solid boundary

Vapour bubble collapse problems lacking spherical symmetry are solved here using a numerical method designed especially for these problems. Viscosity and compressibility in the liquid are neglected. Two specific cases of initially spherical bubbles collapsing near a plane solid wall were simulated: a bubble initially in contact with the wall, and a bubble initially half its radius from the wall at the closest point. It is shown that the bubble develops a jet directed towards the wall rather early in the collapse history. Free surface shapes and velocities are presented at various stages in the collapse. Velocities are scaled like (Δp/ρ)^½ where ρ is the density of the liquid and Δp is the constant difference between the ambient liquid pressure and the pressure in the cavity. For Δp/ρ=10^6cm^2/sec^2 ≈ 1 atm/density of water the jet had a speed of about 130m/sec in the first case and 170m/sec in the second when it struck the opposite side of the bubble. Such jet velocities are of a magnitude which can explain cavitation damage. The jet develops so early in the bubble collapse history that compressibility effects in the liquid and the vapour are not important

Deliberative Constitutionalism in the National Security Setting

Deliberative democracy theory maintains that authentic deliberation about matters of public concern is an essential condition for the legitimacy of political decisions. Such deliberation has two features. The first is deliberative rigor. This is deliberation guided by public-regarding reasons in a process in which persons are genuinely open to the force of the better argument. The second is transparency. This requires that requires that officials publicly explain the reasons for their decisions in terms that citizens can endorse as acceptable grounds for acting in the name of the political community. Such requirements would seem to be especially important in the national security setting, where decisions can have profound life-and-death consequences. Yet this is the setting in which transparency often is least feasible on the part of the Executive branch. Officials may be constrained for good reasons from fully explaining the bases for their decisions. While such reason-giving is especially important to the perceived legitimacy of a decision, anticipating the need to provide it also can enhance deliberative rigor. Limited transparency thus creates the risk both that crucial decisions may not be regarded as legitimate, and that the deliberative process will not be as robust as it should be. In this chapter, we argue that ensuring robust internal deliberative processes in the national security setting can compensate at least to some degree for this limitation. Appreciating the demands of deliberative democracy theory can help inform this process by illuminating how various procedural mechanisms may promote the goals that transparency purports to serve. We focus on the Lawyers Group, which includes senior national security lawyers from across the government, as an example of an arrangement that can help further the ends of deliberative democracy by providing a vehicle for deliberation that meets many, even if not all, of the requirements of that theory. Coordinated by the legal advisor for the National Security Council, this group discusses national security issues that will be presented to the President. We regard our analysis as contributing in two ways to deliberative democratic theory. First, it focuses on the possibility of satisfying the requirement of this theory in a setting in which decision-making often falls short of the demands of full transparency. Second, it suggests how legal analysis may play a distinctive role in the deliberative process. There are limits to what the Lawyers Group can accomplish. We believe, however, that it should be assessed in terms of its contribution to the larger national security deliberative system of which it is a part. From this perspective, the Group’s compliance with several prescriptions of deliberative theory helps it strengthen, even if it does not guarantee, the rigor and persuasiveness of the justifications that the President is able to provide for national security decisions

Collapse of an initially spherical vapor cavity in the neighborhood of a solid boundary

Vapor bubble collapse problems lacking spherical symmetry are solved here using a numerical method designed especially for these problems. Viscosity and compressibility in the liquid are neglected. The method uses finite time steps and features an iterative technique for applying the boundary conditions at infinity directly to the liquid at a finite distance from the free surface. Two specific cases of initially spherical bubbles collapsing near a plane solid wall were simulated: a bubble initially in contact with the wall, and a bubble initially half its radius from the wall at the closest point. It is shown that the bubble develops a jet directed towards the wall rather early in the collapse history. Free surface shapes and velocities are presented at various stages in the collapse. Velocities are scaled like (Δp/ρ)^1/2 where ρ is the density of the liquid and Δp is the constant difference between the ambient liquid pressure and the pressure in the cavity. For Δp/ρ = 10^6 (cm/sec)^2 ~ 1 atm./density of water the jet had a speed of about 130 m/sec in the first case and 170 m/sec in the second when it struck the opposite side of the bubble. Such jet velocities are of a magnitude which can explain cavitation damage. The jet develops so early in the bubble collapse history that compressibility effects in the liquid and the vapor are not important

Identification of Niche Market for Hanwoo Beef: Understanding Korean Consumer Preference for Beef using Market Segment Analysis

Korean Hanwoo beef producers are interested in improving the image of Hanwoo beef for Korean consumers, as the Korean beef market is becoming increasingly open to international competition. This study examines the consumer profile and positioning for the Hanwoo beef product in South Korea. A survey of 480 consumers is conducted to analyze preferences for 33 attributes of beef purchasing decisions. Factor analysis was used to determine factors that are important in beef purchasing decisions, and cluster analysis was used to identify a niche market for branded Hanwoo beef. Factor analysis results indicated that effective labeling and quality assurance of Hanwoo products, the meat quality, price and branding are important to the positioning and marketing of the Hanwoo beef product. Consumers with medium to high income, married and aged between 30 to 39 years, and those that appreciate Hanwoo quality but do not trust the current labeling system are most likely to purchase branded Hanwoo beef and represent a potential niche market, according to cluster analysis results.Beef branding, Market segment analysis, Korean beef market, Consumer/Household Economics, Marketing,

Silicate luminescence and remote compositional mapping

Silicate luminescence and remote compositional mappin

Data visualization within urban models

Models of urban environments have many uses for town planning, pre-visualization of new building work and utility service planning. Many of these models are three-dimensional, and increasingly there is a move towards real-time presentation of such large models. In this paper we present an algorithm for generating consistent 3D models from a combination of data sources, including Ordnance Survey ground plans, aerial photography and laser height data. Although there have been several demonstrations of automatic generation of building models from 2D vector map data, in this paper we present a very robust solution that generates models that are suitable for real-time presentation. We then demonstrate a novel pollution visualization that uses these models

Spectral mixture modeling: Further analysis of rock and soil types at the Viking Lander sites

A new image processing technique was applied to Viking Lander multispectral images. Spectral endmembers were defined that included soil, rock and shade. Mixtures of these endmembers were found to account for nearly all the spectral variance in a Viking Lander image

Compositional variability of the Martian surface

Spectral reflectance data from Viking Landers and Orbiters and from telescopic observations were analyzed with the objective of isolating compositional information about the Martian surface and assessing compositional variability. Two approaches were used to calibrate the data to reflectance to permit direct comparisons with laboratory reference spectra of well characterized materials. In Viking Lander multispectral images (six spectral bands) most of the spectral variation is caused by changes in lighting geometry within individual scenes, from scene to scene, and over time. Lighting variations are both wavelength independent and wavelength dependent. By calibrating lander image radiance values to reflectance using spectral mixture analysis, the possible range of compositions was assessed with reference to a collection of laboratory samples, also resampled to the lander spectral bands. All spectra from the lander images studied plot (in six-space) within a planar triangle having at the apexes the respective spectra of tan basaltic palagonite, gray basalt, and shale. Within this plane all lander spectra fit as mixtures of these three endmembers. Reference spectra that plot outside of the triangle are unable to account for the spectral variation observed in the images