Realistic Placement Research Articles

Numerical construction tests to assess the feasibility of placement grids for Cubipod Homogeneous Low-Crested Structures

Placement grid design is a key phase when constructing armor layers in mound breakwaters. Homogeneous Low-Crested Structures (HLCS) are low-crested structures designed as artificial reefs for marine colonization, coral reef regeneration and beach protection. The placement grid affects the construction feasibility, hydraulic stability and wave transmission of HLCS. This study presents a numerical methodology to simulate a realistic placement procedure for armor units during the construction of HLCS. This numerical simulator is based on the open-source physics engine Bullet Physics Engine (BPE), which applies Newton's laws of motion to rigid bodies. From an initial theorical placement grid for Cubipod HLCS, a series of numerical realistic unit placement tests are carried out to emulate the placement process at prototype scale; placement velocity and spatial deviation of crawler cranes are given parameters associated with each specific project. Considering the placement velocity and spatial deviation during construction, the quality of each specific placement grid is associated with the measured placement errors and the corresponding initial construction deviation to HLCS. This numerical methodology is valuable to understand the influence and the uncertaintly of the construction procedure of armor layers in mound breakwaters.

Multi-criteria method for the realistic placement of water quality sensors on pipes of water distribution systems

This paper aims to solve three issues frequently present in the optimal placement of water quality sensors for protecting water distribution systems (WDSs) from both accidental and intentional contamination, namely i) computational intractability of the optimization problem as the size of the WDS increases, ii) unrealistic assumption that sensors are positioned at nodes, rather than on system pipes, and iii) neglecting site-specific practical conditions impacting on sensor installation. The three drawbacks were tackled by i) restraining the optimization to the hydraulic/topological-wise most important pipes, ii) introducing dummy nodes in the middle of these pipes as potential sensor locations, iii) applying a multi-criteria decision-making tool incorporating urbanistic and economic factors for selecting the most effective sensor locations. The method is tested on the WDS of the town of Parete (Italy), showing the manyfold benefits of the solution obtained.

The geometry of protein hydration.

Based on molecular dynamics simulations of four globular proteins in dilute aqueous solution, with three different water models, we examine several, essentially geometrical, aspects of the protein-water interface that remain controversial or incompletely understood. First, we compare different hydration shell definitions, based on spatial or topological proximity criteria. We find that the best method for constructing monolayer shells with nearly complete coverage is to use a 5 Å water-carbon cutoff and a 4 Å water-water cutoff. Using this method, we determine a mean interfacial water area of 11.1 Å2 which appears to be a universal property of the protein-water interface. We then analyze the local coordination and packing density of water molecules in the hydration shells and in subsets of the first shell. The mean polar water coordination number in the first shell remains within 1% of the bulk-water value, and it is 5% lower in the nonpolar part of the first shell. The local packing density is obtained from additively weighted Voronoi tessellation, arguably the most physically realistic method for allocating space between protein and water. We find that water in all parts of the first hydration shell, including the nonpolar part, is more densely packed than in the bulk, with a shell-averaged density excess of 6% for all four proteins. We suggest reasons why this value differs from previous experimental and computational results, emphasizing the importance of a realistic placement of the protein-water dividing surface and the distinction between spatial correlation and packing density. The protein-induced perturbation of water coordination and packing density is found to be short-ranged, with an exponential decay "length" of 0.6 shells. We also compute the protein partial volume, analyze its decomposition, and argue against the relevance of electrostriction.

Global Positioning System Performance Optimization Using a Normalized Function on Configuration Classes

A mission of the U.S. Air Force Space Command is the positioning of Global Positioning System satellites to improve the accuracy of receiver navigation solutions. To that end, a technique is developed that, given a configuration specifying the number of satellites in each orbital plane, combines a nonlinear program with a simulation to find the constellation that optimizes performance. This approach is greatly expedited by a reduced set of configuration classes, which will result in significantly increased efficiency in computer runtime and constellation management. Additionally, a metric is proposed for constellation performance that normalizes receiver dilution of precision accuracy values and weights trouble spots. A tool implementing the technique and the metric is constructed and applied to three configurations. The first includes the nominal 24-satellite operational constellation, and the other two are for 27 and 31 satellites. For the 24-satellite configuration, satellite positions similar to the nominal constellation are obtained (less than 4° average shift in argument of latitude) and have an improved performance according to at least two metrics, including the new one. This suggests that this approach will be useful for determining unique operationally realistic placement of satellites for other configurations.

Inverse Procedural Modelling of Trees

AbstractProcedural tree models have been popular in computer graphics for their ability to generate a variety of output trees from a set of input parameters and to simulate plant interaction with the environment for a realistic placement of trees in virtual scenes. However, defining such models and their parameters is a difficult task. We propose an inverse modelling approach for stochastic trees that takes polygonal tree models as input and estimates the parameters of a procedural model so that it produces trees similar to the input. Our framework is based on a novel parametric model for tree generation and uses Monte Carlo Markov Chains to find the optimal set of parameters. We demonstrate our approach on a variety of input models obtained from different sources, such as interactive modelling systems, reconstructed scans of real trees and developmental models.

Synthetic event-related potentials: A computational bridge between neurolinguistic models and experiments

Our previous work developed Synthetic Brain Imaging to link neural and schema network models of cognition and behavior to PET and fMRI studies of brain function. We here extend this approach to Synthetic Event-Related Potentials (Synthetic ERP). Although the method is of general applicability, we focus on ERP correlates of language processing in the human brain. The method has two components: Phase 1: To generate cortical electro-magnetic source activity from neural or schema network models; and Phase 2: To generate known neurolinguistic ERP data (ERP scalp voltage topographies and waveforms) from putative cortical source distributions and activities within a realistic anatomical model of the human brain and head. To illustrate the challenges of Phase 2 of the methodology, spatiotemporal information from Friederici’s 2002 model of auditory language comprehension was used to define cortical regions and time courses of activation for implementation within a forward model of ERP data. The cortical regions from the 2002 model were modeled using atlas-based masks overlaid on the MNI high definition single subject cortical mesh. The electromagnetic contribution of each region was modeled using current dipoles whose position and orientation were constrained by the cortical geometry. In linking neural network computation via EEG forward modeling to empirical results in neurolinguistics, we emphasize the need for neural network models to link their architecture to geometrically sound models of the cortical surface, and the need for conceptual models to refine and adopt brain-atlas based approaches to allow precise brain anchoring of their modules. The detailed analysis of Phase 2 sets the stage for a brief introduction to Phase 1 of the program, including the case for a schema-theoretic approach to language production and perception presented in detail elsewhere. Unlike Dynamic Causal Modeling (DCM) and Bojak’s mean field model, Synthetic ERP builds on models of networks that mediate the relation between the brain’s inputs, outputs, and internal states in executing a specific task. The neural networks used for Synthetic ERP must include neuroanatomically realistic placement and orientation of the cortical pyramidal neurons. These constraints pose exciting challenges for future work in neural network modeling that is applicable to systems and cognitive neuroscience.

Realistic placement of plants for virtual environments.

Creating natural forest landscapes for virtual environments (VEs) requires basic knowledge of botany and ecology, without which the terrain might appear synthetic. Although tools such as scene editors have made designers' jobs easier, manually creating a natural-looking landscape is time-consuming. And, depending on the artist's knowledge, the results often don't follow the principles of ecology and spatially viable plant positioning. A proposed approach adopts lessons from ecological modeling to grow vegetation as ground cover for virtual outdoor scenes. It simulates ecologically and spatially realistic placement of plants, from which users can employ the XML-based position data to populate other 2D and 3D VEs. Simulation results show this approach's potential for more complex applications, such as real-time plant growth and state changes in VEs.

Scheduling and Placement of Hardware/Software Real-Time Relocatable Tasks in Dynamically Partially Reconfigurable Systems

With the gradually fading distinction between hardware and software, it is now possible to relocate tasks from a microprocessor to reconfigurable logic and vice versa. However, existing hardware-software scheduling can rarely cope with such runtime task relocation. In this work, we propose a new Relocatable Hardware-Software Scheduling (RHSS) method that not only can be applied to dynamically relocatable hardware-software tasks, but also increases the reconfigurable hardware resource utilization, reduces the reconfigurable hardware resource fragmentation with realistic placement methods, and makes best efforts at meeting the real-time constraints of tasks. The feasibility of the proposed relocatable hardware-software scheduling algorithm was proved by applying it to some randomly generated examples and a real dynamically reconfigurable network security system example. Compared to the quadratic time complexity of the state-of-the-art Adaptive Hardware-Software Allocation (AHSA) method, RHSS is linear in time complexity, and improves the reconfigurable hardware utilization by as much as 117.8%. The scheduling and placement time and the memory usage are also drastically reduced by as much as 89.5% and 96.4%, respectively.

Simultaneous cutting of coupled tetrahedral and triangulated meshes and its application in orbital reconstruction

Recently, advances in imaging techniques for diagnostics and associated technologies have led to an improved preoperative planning for craniomaxillofacial surgeons. In particular, the application of navigation-aided procedures for orbital reconstruction has proved to be essential. Preforming orbital implants for orbital floor reconstruction and determining overcorrection with regard to the orbital floor reconstruction could be achieved using preoperative planning. It has turned out that the computation of soft tissue cuts is an essential prerequisite for the realistic placement of implants. We propose a simulation framework that allows for the static and dynamic cutting of soft and hard tissue representations. The framework comprises components to model tissue deformation, cutting of tissue and interaction between the physical bodies. Furthermore, volume and surface representations are decoupled which allows for an independent scaling in the complexity of the representations and, therefore, in the simulation and visualisation performance. In contrast to many other cutting approaches, our algorithm handles both representations simultaneously. The framework is used to simulate the realistic insertion of a preformed orbital implant model through the soft tissue cut and the prediction of the postoperative eye bulb position. Experiments show that the framework can be used to determine overcorrection and to preform orbital implants.

Policy and knowledge in fisheries management: a policy briefa

Abstract Schwach, V., Bailly, D., Christensen, A-S., Delaney, A. E., Degnbol, P., van Densen, W. L. T., Holm, P., McLay, H. A., Nielsen, K. N., Pastoors, M. A., Reeves, S. A., and Wilson, D. C. 2007. Policy and knowledge in fisheries management: a policy brief. – ICES Journal of Marine Science, 64: 798–803. The EU project Policy and Knowledge in Fisheries Management investigated the use of biological knowledge in various parts of the fisheries system, using North Sea cod as a case study. The project examined the way scientific advice was generated from technical and institutional perspectives, as well as the way claims about science appeared in both policy-setting and in public debate through the press. The results suggested that many people involved in the system want a new way to reflect about science in management. People from all major stakeholder groups are calling for a more interactive system of producing a common knowledge base. Such a system could bring uncertainty from its current marginal role as the leftovers of certainty to the heart of the science process. It would require stakeholders to help address uncertainty and to negotiate a more realistic placement of burden of proof.

Adoption in Korea: current status and future prospects

This article examines the current status of adoption in Korea and discusses the issues that must be addressed for future development. The nature of adoption has changed dramatically in the last 50 years, and continues to change in Korea. If the first half of modern adoption history were about finding and providing permanent homes for war orphans and children abandoned out of destitution, the second half saw increasing demand for adoption to function as a key component of the continuum of child welfare services providing care for children who need protection and care outside their home. However, responding to this change has been a challenge over the years. Based on the analysis of recent trends of the child welfare system and adoption in Korea, this article reveals that there are significant barriers in the path to improving adoption, especially domestic adoption, so that it can be considered a realistic placement option for children who need protection and care in Korea. Suggestions for the future direction of reforming adoption policy and practice are given.

Student nurse theatre placements. The new curriculum.

Following the implementation of the Fitness for Practice (FFP) nurse education curriculum, opportunities are available for student nurses to return to the operating theatre environment during their surgical module. This follows a ten-year absence in most parts of Wales. This article investigates what realistic placement objectives are available for student nurses in Wales and how close mentor supervision can enhance the learning process and promote the clinical experience of theatre nursing.

Boosters for driving long onchip interconnects - design issues, interconnect synthesis, and comparison with repeaters

Trends in complementary metal-oxide-semiconductor (CMOS) technology and very large scale integration architectures are causing interconnect to play an increasing role in overall performance, power consumption, and design effort. Traditionally, repeaters are used for driving long onchip interconnects. However, recent studies indicate that repeaters are using increasing area, power, and design resources and are inherently limited in how much they can improve the performance (Adler and Friedman, 1998), (Sylvester and Keutzer, 1999), (Cong and Pan, 1999). The unidirectionality of repeaters also limits their applicability in multisourced lines. This paper presents a new circuit called the Booster that compares favorably with repeaters for driving long lines in terms of area, performance, power, and placement sensitivity. Boosters also have the advantage of being bidirectional and providing a low impedance termination to improve signal integrity. Driver edge rates are reduced and peak power is drastically reduced compared to repeaters, thus, improving signal integrity and mitigating inductive effects. Boosters are shown to be more than 20% faster for driving a variety of interconnect loads over conventional repeaters in a 0.16-/spl mu/m CMOS technology. Boosters are typically inserted three times less frequently than repeaters for optimal performance, resulting in fewer boosters for driving the same interconnect lengths and, hence, saving on area, power, and placement effort. Computer-aided design tools for global interconnect synthesis need to support a wider variety of circuit techniques such as boosters. Other exotic circuit techniques such as differential, dynamic, or low-swing techniques require significantly more custom circuit design, noise analysis, extra timing signals, or extra power supplies and are, hence, cumbersome for automatic interconnect synthesis tools. In contrast, the proposed boosters can be inserted on lines in a straightforward manner much like repeaters. Based on analytical delay models, we derive rules for insertion and sizing of boosters that can easily be incorporated into an interconnect synthesis tool. We formulate design rules that determine: 1) the number of boosters needed; 2) their placements; and 3) device sizes for driving a given interconnect load. The primary objective function is minimizing delay and then area and power. Power analysis is slightly more complex than for repeaters so we present a systematic design approach. A placement sensitivity analysis comparing boosters and repeaters is used to study the effects of realistic placement constraints that arise in microprocessor floorplans. We conclude by discussing various design tradeoffs between repeater and booster-based interconnect designs. We then present other potential applications of boosters in domino logic designs, multisource/multisink buses, and field programmable gate array interconnection network designs in addition to conventional point-to-point interconnection lines.

Modeling of interaction of electromagnetic fields from a cellular telephone with hearing aids

The new generation of cellular telephones and other personal communication services (PCSs) poses new problems and challenges in interactions with the human body, Among them is electromagnetic interference (EMI) with medical devices, particularly for systems using time-division multiple access (TDMA). Hearing aids are among the devices affected by the pulse modulation in the audio range associated with the TDMA systems. While EMI in this case does not generally pose a health risk, it constitutes a considerable annoyance, which may prevent the hearing-aid wearers from using some of the new communication devices. Also, just proximity to the devices used by others or the base station may result in signals sufficient to interfere with proper perception of sounds, We have evaluated the electric and magnetic fields in the ear canal at 900 MHz for a typical monopole antenna on a typical handset, an equivalent dipole, and a plane wave. Special care was taken to properly represent the anatomy of the ear, including its canal. The finite-difference time-domain (FDTD) method was used to compute the electric and magnetic fields in the ear canal and around the ear. The fields from the exposure sources in various realistic placements of the hearing aid were compared. The results presented are of importance and use in developing performance standards and practical testing methods for various types of hearing aids.

A method for spatial and temporal assessment of gastropod grazing intensity in the field: the use of radula scrapes on wax surfaces

The feeding apparatus of many marine molluscan herbivores leaves distinctive marks on the surface of dental wax. This method can be used in the field to assess the spatial and temporal patterns of gastropod grazing on rocky shores. Among the common gastropod grazers of intertidal habitats on the Isle of Man, distinctive rasping marks were made by docoglossan ( Patella vulgata.), rhipidoglossan ( Calliostoma zizyphinum. and Gibbula spp.) and larger taenioglossan ( Littorina obtusata.) grazers. Our technique for the field deployment of wax surfaces is simple, inexpensive, and permits a realistic placement of the wax surface in the environment. This placement is achieved by casting the wax into small discs (14 mm diameter) and setting them into pre-formed holes in the rock surface. By quantifying either the number of discs scraped or the area of the wax surface scraped, patterns of grazing intensity (defined as areal extent of the surface grazed in a given period) can be assessed over a variety of spatial and temporal scales. To illustrate this method and refine its use, we recorded the grazing patterns of the limpet Patella vulgata for periods from 12 h to 17 days. The optimal period of deployment depended on the specific habitat, but we often found periods of 1–14 days to be appropriate. Regular arrays of discs also demonstrated that grazing intensity was spatially variable at a scale of 0.25 m, and that grazing intensity increased throughout the late winter and spring. This method provides a cheap and direct measure of feeding intensity that is directly relevant to understanding the effect of grazing molluscs on algal communities. Moreover, it can be used over a variety of spatial and temporal scales.