991 resultados para basic block reduce


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We tagged a total of 14 yellowtail snapper (Ocyurus chrysurus Bloch 1790) and black grouper (Mycteroperca bonaci Poey 1860) inside the Conch Reef Research Only Area (a no-take marine reserve) in the northern Florida Keys National Marine Sanctuary in November 2001. Both species are heavily exploited in the region. Our objective was to characterize site fidelity and movement behavior along the reef tract to the north and south of the release point. Fishes were collected by baited hook and line from the surface, surgically-tagged with coded-acoustic transmitters, and returned to the reef by snorkelers. Tracking of fish movement behavior was conducted by five acoustic receivers deployed on the seafloor from Davis Reef in the south to Pickles Reef in the north. Fishes were tracked for up to eight months. Results indicated that the majority of signal detections for individual fish from both species were recorded at the two Conch Reef receivers. Limited movement from Conch Reef to Davis Reef was recorded, but no signal detections were recorded at the two sites to the north of Conch Reef. These results suggest that both species show site fidelity to Conch Reef. Future studies will seek to characterize this site fidelity with increased temporal and spatial resolution at Conch Reef. (PDF contains 25 pages.)

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One third of the people on earth who are described as living in absolute poverty are found today in India. “These people,” says Mr B K Satpathy, “are caught in a poverty trap’.” “Poverty trap?” we ask. “These are creative weavers; their cloth has a distinctive style, but those who supply their thread also take away and sell the cloth, paying just a small labor cost for each saree. If they are skilled and work hard this amounts to only 25-30 rupees (60-70 US cents) per day.” Under this arrangement, weaving does not provide enough to live on, and people are seeking ways to escape their entrapment in poverty. (Pdf contains 6 pages).

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The microgravity research, as a branch of the advanced sciences and a spe- cialized field of high technology, has been made in China since the late 1980's. The research group investigating microgravity fluid physics consisted of our col- leagues and the authors in the Institute of Mechanics of the Chinese Academy of Sciences (CAS), and we pay special attention to the floating zone convection as our first research priority. Now, the research group has expanded and is a part of the National Microgravity Laboratory of the CAS, and the research fields have been extended to include more subjects related to microgravity science. Howev- er, the floating zone convection is still an important topic that greatly holds our research interests.

目录

1. models of floating zone convection
1.1 floating-zone crystal growth
1.2 physical model
1.3 hydrodynamic model
1.4 mathematical model
references
2. basic features of floating zone convection
2.1 equations and boundary conditions
2.2 simple solutions of fz convection
2.3 solution for two-layers flow
2.4 numerical simulation
2.5 onset of oscillation
references
3. experimental method of fz convection
3.1 ground-based simulation experiments for pr≥1
3.2 temperature and velocity oscillations
3.3 optical diagnostics of free surface oscillation
3.4 critical parameters
3.5 microgravity experiments
3.6 ground-based simulation experiment for pr《1
.references
4. mechanism on the onset of oscillatory convection
4.1 order of magnitude analysis
4.2 mechanism of hydrothermal instability
4.3 linear stability analysis
4.4 energy instability of thermocapillary convection
4.5 unsteady numerical simulation of 2d and 3d
4.6 two bifurcation transitions in the case of small pr number fluid
4.7 two bifurcation transitions in the case of large pr number fluid
4.8 transition to turbulence
references
5. liquid bridge volume as a critical geometrical parameter
5.1 critical geometrical parameters
5.2 ground-based and mierogravity experiments
5.3 instability analyses of a large prandtl number (pr≥1)fluid
5.4 instability analyses of a small prandtl number (pr《1)fluid
5.5 numerical simulation on two bifurcation process
references
6. theoretical model of crystal growth by the floating zone method
6.1 concentration distribution in a pure diffusion process
6.2 solutal capillary convection and diffusion
6.3 coupling with phase change convection
6.4 engineering model of floating zone technique
references
7. influence of applied magnetic field on the fz convection
7.1 striation due to the time-dependent convection
7.2 applied steady magnetic field and rotational magnetic field
7.3 magnetic field design for floating half zone
7.4 influence of magnetic field on segregation
references
8. influence of residual acceleration and g-jitter
8.1 residual acceleration in microgravity experiments
8.2 order of magnitude analyses (oma)
8.3 rayleigh instability due to residual acceleration
8.4 ground-based experiment affected by a vibration field
8.5 numerical simulation of a low frequency g-jitter
8.6 numerical simulation of a high frequency g-jitter
references

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This book elucidates the methods of molecular gas dynamics or rarefied gas dynamics which treat the problems of gas flows when the discrete molecular effects of the gas prevail under the circumstances of low density, the emphases being stressed on the basis of the methods, the direct simulation Monte Carlo method applied to the simulation of non-equilibrium effects and the frontier subjects related to low speed microscale rarefied gas flows. It provides a solid basis for the study of molecular gas dynamics for senior students and graduates in the aerospace and mechanical engineering departments of universities and colleges. It gives a general acquaintance of modern developments of rarefied gas dynamics in various regimes and leads to the frontier topics of non-equilibrium rarefied gas dynamics and low speed microscale gas dynamics. It will be also of benefit to the scientific and technical researchers engaged in aerospace high altitude aerodynamic force and heating design and in the research on gas flow in MEMS

  • 目次内容                                                                
[1]  Molecular structure and energy states (21)  
 
[2]  Some basic concepts of kinetic theory (51)  
 
[3]  Interaction of molecules with solid surface (131)  
 
[4]  Free molecular flow (159)  
 
[5]  Continuum models (191)  
 
[6]  Transitional regime (231)  
 
[7]  Direct simulation Monte-Carlo (DSMC) method (275)  
 
[8]  Microscale slow gas flows, information preservation method (317)  
 
[App. I]  Gas properties (367)  
 
[App. II]  Some integrals (369)  
 
[App. III]  Sampling from a prescribed distribution (375)  
 
[App. IV]  Program of the couette flow (383)  
 
Subject Index (399)  

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Radar services are occasionally affected by wind farms. This paper presents a comprehensive description of the effects that a wind farm may cause on the different radar services, and it compiles a review of the recent research results regarding the mitigation techniques to minimize this impact. Mitigation techniques to be applied at the wind farm and on the radar systems are described. The development of thorough impact studies before the wind farm is installed is presented as the best way to analyze in advance the potential for interference, and subsequently identify the possible solutions to allow the coexistence of wind farms and radar services.

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Age reading by use of otoliths is one of the basic but also most essential elements in practical fish population dynamics. Unfortunately, many factors can influence the readings of a single reader. Erronous readings, however, have a consequential effect on the evaluation and prediction of the development of the fish stock under consideration. In order to master this problem and to reduce out the effect of those factors, it seems neccessary to standardize the whole process of age reading between collaborating readers. From a statistical point of view calibration techniques can be used to identify those factors and to correct the readings with respect to them. The current article presents an overview over the basic idea behind this, over how to balance out the existing deviations and how to correct the age readings.

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Energy functions (or characteristic functions) and basic equations for ferroelectrics in use today are given by those for ordinary dielectrics in the physical and mechanical communications. Based on these basic equations and energy functions, the finite element computation of the nonlinear behavior of the ferroelectrics has been carried out by several research groups. However, it is difficult to process the finite element computation further after domain switching, and the computation results are remarkably deviating from the experimental results. For the crack problem, the iterative solution of the finite element calculation could not converge and the solutions for fields near the crack tip oscillate. In order to finish the calculation smoothly, the finite element formulation should be modified to neglect the equivalent nodal load produced by spontaneous polarization gradient. Meanwhile, certain energy functions for ferroelectrics in use today are not compatible with the constitutive equations of ferroelectrics and need to be modified. This paper proposes a set of new formulae of the energy functions for ferroelectrics. With regard to the new formulae of the energy functions, the new basic equations for ferroelectrics are derived and can reasonably explain the question in the current finite element analysis for ferroelectrics.

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A new high-order finite volume method based on local reconstruction is presented in this paper. The method, so-called the multi-moment constrained finite volume (MCV) method, uses the point values defined within single cell at equally spaced points as the model variables (or unknowns). The time evolution equations used to update the unknowns are derived from a set of constraint conditions imposed on multi kinds of moments, i.e. the cell-averaged value and the point-wise value of the state variable and its derivatives. The finite volume constraint on the cell-average guarantees the numerical conservativeness of the method. Most constraint conditions are imposed on the cell boundaries, where the numerical flux and its derivatives are solved as general Riemann problems. A multi-moment constrained Lagrange interpolation reconstruction for the demanded order of accuracy is constructed over single cell and converts the evolution equations of the moments to those of the unknowns. The presented method provides a general framework to construct efficient schemes of high orders. The basic formulations for hyperbolic conservation laws in 1- and 2D structured grids are detailed with the numerical results of widely used benchmark tests. (C) 2009 Elsevier Inc. All rights reserved.

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The work presented in this thesis revolves around erasure correction coding, as applied to distributed data storage and real-time streaming communications.

First, we examine the problem of allocating a given storage budget over a set of nodes for maximum reliability. The objective is to find an allocation of the budget that maximizes the probability of successful recovery by a data collector accessing a random subset of the nodes. This optimization problem is challenging in general because of its combinatorial nature, despite its simple formulation. We study several variations of the problem, assuming different allocation models and access models, and determine the optimal allocation and the optimal symmetric allocation (in which all nonempty nodes store the same amount of data) for a variety of cases. Although the optimal allocation can have nonintuitive structure and can be difficult to find in general, our results suggest that, as a simple heuristic, reliable storage can be achieved by spreading the budget maximally over all nodes when the budget is large, and spreading it minimally over a few nodes when it is small. Coding would therefore be beneficial in the former case, while uncoded replication would suffice in the latter case.

Second, we study how distributed storage allocations affect the recovery delay in a mobile setting. Specifically, two recovery delay optimization problems are considered for a network of mobile storage nodes: the maximization of the probability of successful recovery by a given deadline, and the minimization of the expected recovery delay. We show that the first problem is closely related to the earlier allocation problem, and solve the second problem completely for the case of symmetric allocations. It turns out that the optimal allocations for the two problems can be quite different. In a simulation study, we evaluated the performance of a simple data dissemination and storage protocol for mobile delay-tolerant networks, and observed that the choice of allocation can have a significant impact on the recovery delay under a variety of scenarios.

Third, we consider a real-time streaming system where messages created at regular time intervals at a source are encoded for transmission to a receiver over a packet erasure link; the receiver must subsequently decode each message within a given delay from its creation time. For erasure models containing a limited number of erasures per coding window, per sliding window, and containing erasure bursts whose maximum length is sufficiently short or long, we show that a time-invariant intrasession code asymptotically achieves the maximum message size among all codes that allow decoding under all admissible erasure patterns. For the bursty erasure model, we also show that diagonally interleaved codes derived from specific systematic block codes are asymptotically optimal over all codes in certain cases. We also study an i.i.d. erasure model in which each transmitted packet is erased independently with the same probability; the objective is to maximize the decoding probability for a given message size. We derive an upper bound on the decoding probability for any time-invariant code, and show that the gap between this bound and the performance of a family of time-invariant intrasession codes is small when the message size and packet erasure probability are small. In a simulation study, these codes performed well against a family of random time-invariant convolutional codes under a number of scenarios.

Finally, we consider the joint problems of routing and caching for named data networking. We propose a backpressure-based policy that employs virtual interest packets to make routing and caching decisions. In a packet-level simulation, the proposed policy outperformed a basic protocol that combines shortest-path routing with least-recently-used (LRU) cache replacement.

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A total of 61 specimens of Heterotis niloticus were evaluated by linear regression and correlation. The specimens had mean standard length of 27.09 plus or minus 4.73cm, total length of 33-49cm, mean weight of 2445,108.3g, mean snout length of 48 plus or minus 0.86cm, mean eye diameter of 1.30 plus or minus 0.15cm, mean head length of 6.29 plus or minus 1.75cm. There was a strong relationship between the length and the weight, the eye diameter and the standard length, snout length and the standard length, head length and the standard length, snout length and the weight, head length and the weight (P<0.05). But the correlation of the eye diameters and the weight was insignificant (P>0.05). The growth pattern analysis depicts that the growth was negatively allometric with a b value of 1.16

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The development of Ring Opening Metathesis Polymerization has allowed the world of block copolymers to expand into brush block copolymers. Brush block copolymers consist of a polymer backbone with polymeric side chains, forcing the backbone to hold a stretched conformation and giving it a worm-like shape. These brush block copolymers have a number of advantages over tradition block copolymers, including faster self-assembly behavior, larger domain sizes, and much less entanglement. This makes them an ideal candidate in the development of a bottom-up approach to forming photonic crystals. Photonic crystals are periodic nanostructures that transmit and reflect only certain wavelengths of light, forming a band gap. These are used in a number of coatings and other optical uses. One and two dimensional photonic crystals are commercially available, though are often expensive and difficult to manufacture. Previous work has focused on the creation of one dimensional photonic crystals from brush block copolymers. In this thesis, I will focus on the synthesis and characterization of asymmetric brush block copolymers for self-assembly into two and three dimensional photonic crystals. Three series of brush block copolymers were made and characterized by Gel Permeation Chromatography and Nuclear Magnetic Resonance spectroscopy. They were then made into films through compressive thermal annealing and characterized by UV-Vis Spectroscopy and Scanning Electron Microscopy. Evidence of non-lamellar structures were seen, indicating the first reported creation of two or three dimensional photonic crystals from brush block copolymers.

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From the steam turbines which provide most of our electricity to the jet engines which have shrunk our World, turbomachines undoubtedly play a major role in life today. Competition in the turbomachinery industry is fiercely strong [Wisler, 1998], hence good aerodynamic design is vital. However, with efficiency levels already close to their theoretical maxima, companies are increasingly looking to reduce costs and increase reliability through improved design practice. Computational Fluid Dynamics (CFD) can make a strong contribution to assisting this process as it has the potential to increase performance while reducing cost. The situation is, however, complicated by an ever decreasing number of engineers with sufficient design experience to reap the full benefits offered by CFD. With the large risks involved, novice designers of today are increasingly confined to refining old designs rather than gaining experience, like their forebears, through 'clean sheet' exercises. Hence it is desirable to capture the knowledge and experience of older designers, before it is lost, to assist the engineers of tomorrow. It is therefore the aim of this project to produce a design support tool which will not only store the appropriate CFD codes, but also provide a dynamic signpost (based on elicited knowledge and experience) to advise the engineer in their use. The signposting methodology developed for the aerospace industry [Clarkson and Hamilton, 1997] will provide the basic framework for the tool. This paper reviews current turbomachinery design practice (including an examination of the relevant CFD) in order to establish the important issues which a support tool must address. Current design support methodologies and their propriety are then reviewed, followed by a detailed description of the signposting concept. It then sets out a clear statement of the objectives for the research and the methods proposed to meet them. The paper concludes with a timetable of the work.