16,000 research outputs found
Mineralogical, optical, geochemical, and particle size properties of four sediment samples for optical physics research
X-ray diffraction and spectroscopy were used to investigate the mineralogical and chemical properties of the Calvert, Ball Old Mine, Ball Martin, and Jordan Sediments. The particle size distribution and index of refraction of each sample were determined. The samples are composed primarily of quartz, kaolinite, and illite. The clay minerals are most abundant in the finer particle size fractions. The chemical properties of the four samples are similar. The Calvert sample is most notably different in that it contains a relatively high amount of iron. The dominant particle size fraction in each sample is silt, with lesser amounts of clay and sand. The indices of refraction of the sediments are the same with the exception of the Calvert sample which has a slightly higher value
Scaling properties of velocity and temperature spectra above the surface friction layer in a convective atmospheric boundary layer
International audienceWe report velocity and temperature spectra measured at nine levels from 1.42 meters up to 25.7 m over a smooth playa in Western Utah. Data are from highly convective conditions when the magnitude of the Obukhov length (our proxy for the depth of the surface friction layer) was less than 2 m. Our results are somewhat similar to the results reported from the Minnesota experiment of Kaimal et al. (1976), but show significant differences in detail. Our velocity spectra show no evidence of buoyant production of kinetic energy at at the scale of the thermal structures. We interpret our velocity spectra to be the result of outer eddies interacting with the ground, not "local free convection". We observe that velocity spectra represent the spectral distribution of the kinetic energy of the turbulence, so we use energy scales based on total turbulence energy in the convective boundary layer (CBL) to collapse our spectra. For the horizontal velocity spectra this scale is (zi ?o)2/3, where zi is inversion height and ?o is the dissipation rate in the bulk CBL. This scale functionally replaces the Deardorff convective velocity scale. Vertical motions are blocked by the ground, so the outer eddies most effective in creating vertical motions come from the inertial subrange of the outer turbulence. We deduce that the appropriate scale for the peak region of the vertical velocity spectra is (z ?o)2/3 where z is height above ground. Deviations from perfect spectral collapse under these scalings at large and small wavenumbers are explained in terms of the energy transport and the eddy structures of the flow. We find that the peaks of the temperature spectra collapse when wavenumbers are scaled using (z1/2 zi1/2). That is, the lengths of the thermal structures depend on both the lengths of the transporting eddies, ~9z, and the progressive aggregation of the plumes with height into the larger-scale structures of the CBL. This aggregation depends, in top-down fashion, on zi. The whole system is therefore highly organized, with even the smallest structures conforming to the overall requirements of the whole flow
Stochastic Reinforcement Learning
In reinforcement learning episodes, the rewards and punishments are often
non-deterministic, and there are invariably stochastic elements governing the
underlying situation. Such stochastic elements are often numerous and cannot be
known in advance, and they have a tendency to obscure the underlying rewards
and punishments patterns. Indeed, if stochastic elements were absent, the same
outcome would occur every time and the learning problems involved could be
greatly simplified. In addition, in most practical situations, the cost of an
observation to receive either a reward or punishment can be significant, and
one would wish to arrive at the correct learning conclusion by incurring
minimum cost. In this paper, we present a stochastic approach to reinforcement
learning which explicitly models the variability present in the learning
environment and the cost of observation. Criteria and rules for learning
success are quantitatively analyzed, and probabilities of exceeding the
observation cost bounds are also obtained.Comment: AIKE 201
An analysis of airline landing flare data based on flight and training simulator measurements
Landings by experienced airline pilots transitioning to the DC-10, performed in flight and on a simulator, were analyzed and compared using a pilot-in-the-loop model of the landing maneuver. By solving for the effective feedback gains and pilot compensation which described landing technique, it was possible to discern fundamental differences in pilot behavior between the actual aircraft and the simulator. These differences were then used to infer simulator fidelity in terms of specific deficiencies and to quantify the effectiveness of training on the simulator as compared to training in flight. While training on the simulator, pilots exhibited larger effective lag in commanding the flare. The inability to compensate adequately for this lag was associated with hard or inconsistent landings. To some degree this deficiency was carried into flight, thus resulting in a slightly different and inferior landing technique than exhibited by pilots trained exclusively on the actual aircraft
Fashionable Loafers for Male Students
Male students of the Department of Integrated Rural Art and Industry, Kwame Nkrumah University of Science and Technology, Kumasi have preference for three kinds of footwear: loafers, boots, and dressing shoes. They rate loafers as highly preferred for three main reasons: trendiness, adaptability, and economy. This research aimed to design and produce fashionable loafers for male students. The descriptive research method was used to give details about the tools and materials used for the footwear, and the processes for making the loafers. The participatory product design method was used, where the would-be users of the footwear were involved in the design process – they were consulted for their views and comments right from the early design stages till actualisation of the product. The target population was 150 male students of the said Department; 100 were accessible. The simple random sampling method was used; data was collected through interviews and observation. The study recognised that the popularity, acceptability or attractiveness of the first pair of loafers can be seen in 3 ways: African wear or the look alike, the use of beads, and youthfulness of colour. Adaptability and economy of footwear do show up in the varied application of colour and material, for multipurpose use of the footwear. The integration of locally obtainable materials (beads, fabric and leather) and necessary design factors were determined after which manufacturing operations such as pattern cutting, closing, lasting, attaching, arrangement of beads, and finishing were gone through to realize the shoes. Two pairs of loafers were produced; one has bright and lively colours, the other, relatively darker but appealing colours. Keywords: Male students, fashionable, loafers, adaptability, econom
2D linear friction weld modelling of a Ti-6Al-4V T-joint
Most examples of linear friction weld process models have focused on joining two identically shaped workpieces. This article reports on the development of a 2D model, using the DEFORM finite element package, to investigate the joining of a rectangular Ti-6Al-4V workpiece to a plate of the same material. The work focuses on how this geometry affects the material flow, thermal fields and interface contaminant removal. The results showed that the material flow and thermal fields were not even across the two workpieces. This resulted in more material expulsion being required to remove the interface contaminants from the weld line when compared to joining two identically shaped workpieces. The model also showed that the flash curves away from the weld due to the rectangular upstand "burrowing" into the base plate.Understanding these critical relationships between the geometry and process outputs is crucial for further industrial implementation of the LFW process.EPSRC, The Welding Institut
Charged Black Cosmic String
Global U(1) strings with cylindrical symmetry are studied in anti-de Sitter
spacetime. According as the magnitude of negative cosmological constant, they
form regular global cosmic strings, extremal black cosmic strings and charged
black cosmic strings, but no curvature singularity is involved. The
relationship between the topological charge of a neutral global string and the
black hole charge is clarified by duality transformation. Physical relevance as
straight string is briefly discussed.Comment: ll pages, LaTe
Beef Cattle Production and Management Practices and Implications for Educators
Beef producers need to continually incorporate new information and adopt new technology to effectively manage production costs. Oklahoma State University began a Master Cattleman program with this need in mind. Understanding technology adoption by producers requires identifying current management practices. Data from a survey developed as part of the Master Cattleman program document current practices. Management practices were examined for two groups; producers with smaller herds who are less dependent on the beef enterprise for family income, and producers with larger herds who are more dependent on beef. Results clearly show that size and dependence on the beef enterprise matters when considering a broad spectrum of beef management practices.Livestock Production/Industries,
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