Three-dimensional Spatial Model Research Articles

Design of a highly stable, high-conversion-efficiency, optical parametric chirped-pulse amplification system with good beam quality

An optical parametric chirped-pulse amplifier (OPCPA) design that provides 40% pump-to-signal conversion efficiency and over-500-mJ signal energy at 1054 nm for front-end injection into a Nd:glass amplifier chain is presented. This OPCPA system is currently being built as the prototype front end for the OMEGA EP (extended performance) laser system at the University of Rochester's Laboratory for Laser Energetics. Using a three-dimensional spatial and temporal numerical model, several design considerations necessary to achieve high conversion efficiency, good output stability, and good beam quality are discussed. The dependence of OPCPA output on the pump beam's spatiotemporal shape and the relative size of seed and pump beams is described. This includes the effects of pump intensity modulation and pump-signal walk-off. The trade-off among efficiency, stability, and low output beam intensity modulation is discussed.

A three-dimensional spatial fading correlation model for uniform rectangular arrays

A closed-form expression for the spatial fading correlation function of a uniform rectangular array (URA) in a three-dimensional (3D) multipath channel is derived. The fading correlation function is expressed in terms of both the azimuth and elevation angle of arrival as well as the antenna spacing and geometry of the URA. Verification is achieved by means of computer simulation where the theoretical and simulation results are shown to be in good agreement. Our results demonstrate that azimuth spread (AS) is the primary determinant of the antenna correlation and the impact of the elevation spread is mainly noticeable at low AS values. The results obtained are vital for capacity analysis in multiple-input multiple-output systems, as well as for sensitivity analysis of the antenna array under study.

A three-dimensional spatial model for plant competition in an heterogeneous soil environment

The model described in this paper, the three-dimensional model for the interaction of plants and soil (3DMIPS), was developed to explore how the growth and competitive ability of plants is affected by the interactions between the size and scaling properties of their root systems and the spatial properties of the resources they consume. The main characteristics of the model are as follows. (1) The soil model simulates the spatiotemporal dynamics of temperature, water and solutes (nutrients) in a heterogeneous, 3-dimensional (3-D) soil profile. (2) The plant model has a 3-D simulation of root architecture and plasticity (the ability of certain plants to redirect root growth to areas with high soil nutrient concentration). Plant root architecture is a key component in the simulation of plant nutrient uptake and transpiration. (3) The model simulates the spatiotemporal dynamics of live root, dead root, live shoot, standing dead, and litter biomass and nutrients of individual plants. It simulates the translocation of biomass and nutrients between roots and shoots as a function of plant growth, nutrient uptake, defoliation, regrowth, senescence, and changes in environmental condition. The author presents two set of simulation results. The first set consist of model validation experiments where the author compares model results with data from experiments designed to test the model's ability to predict plant growth and competition in a heterogeneous soil nutrient environment. Model and experimental results were statistically similar in 297 of the 408 variables analyzed. Experimental and modeled variables that were statistically different, were nevertheless highly correlated, with the difference between model and experimental results averaging ±28%. The second set of simulations was designed to assess how plant growth can be affected by an interaction between root lateral spread and the supply rate and spatial distribution of soil nutrients. Results showed that the competitive ability, distribution, and performance of plants could be linked in part to interactions among the size, uptake rates, and scaling properties of their root systems and the supply rate and spatial distribution of the nutrients they utilize. Comparisons are made with the SPUR, PHOENIX, CENTURY, and GEM grassland models. Computer codes and instructions for the implementation of 3DMIPS are available from the author.

Physical Modeling of Line-of-Sight Wideband Propagation in a City Street for Microcellular Communication

This paper proposes a three-dimensional (3D) spatial variant wideband multi-ray model for line-of-sight radio wave propagation in a city street. An analytical expression of the spatial variant channel transfer function is derived. The model provides 3D propagation information for both the base and mobile stations, e.g., direction of arrival, which makes it useful in antenna array applications. The developed model can be used to predict both wideband, e.g., angle and delay spread, and narrowband, e.g., path loss, propagation characteristics in a city street with any number of crossing streets of different widths. The proposed 3D wideband model is compared with an experimentally verified two-ray wideband model described in [18]. The model is easy to implement and fast to compute since there is no searching for coupling rays.

Physical Modeling of Line-of-Sight Wideband Propagation in a City Street for Microcellular Communication

This paper proposes a three-dimensional (3D) spatial variant wideband multi-ray model for line-of-sight radio wave propagation in a city street. An analytical expression of the spatial variant channel transfer function is derived. The model provides 3D propagation information for both the base and mobile stations, e.g., direction of arrival, which makes it useful in antenna array applications. The developed model can be used to predict both wideband, e.g., angle and delay spread, and narrowband, e.g., path loss, propagation characteristics in a city street with any number of crossing streets of different widths. The proposed 3D wideband model is compared with an experimentally verified two-ray wideband model described in [18]. The model is easy to implement and fast to compute since there is no searching for coupling rays.

A design of three-dimensional spatial data model and its data structure in geological exploration engineering

The key to develop 3-D GISs is the study on 3-D data model and data structure. Some of the data models and data structures have been presented by scholars. Because of the complexity of 3-D spatial phenomenon, there are no perfect data structures that can describe all spatial entities. Every data structure has its own advantages and disadvantages. It is difficult to design a single data structure to meet different needs. The important subject in the 3-D data models is developing a data model that has integrated vector and raster data structures. A special 3-D spatial data model based on distributing features of spatial entities should be designed. We took the geological exploration engineering as the research background and designed an integrated data model whose data structures integrats vector and raster data by adopting object-oriented technique. Research achievements are presented in this paper.

From highly relevant to not relevant: examining different regions of relevance

User relevance judgments are central to both the systems and user-oriented approaches to information retrieval (IR) systems research and development. User-oriented relevance research has also operated on two largely unconnected tracks. First, a relevance level track that examines users' criteria for relevance judgments. Second, a regions of relevance track that examines the measurement of users' relevance judgments. Users judgments and criteria for highly relevant items have been central issues for much of the relevance research. Findings are presented from four separate studies of relevance judgments by 55 users, conducting their initial online search on a particular information problem. In three studies, the number of items judged “partially” relevant (on a scale of relevant, partially relevant or not relevant) was positively correlated with different aspects of changes in users', including: (1) information problem definition, (2) search intermediaries' perceptions that a user's question and information problem has changed during the mediated search interaction, (3) personal knowledge due to the search interaction, and (4) criteria for making relevance judgments. Users with high knowledge and topic levels were more likely to judge items as highly relevant. Differences between users' criteria for highly, partially and non-relevant items are also identified. Findings suggest the need to expand the framework for relevance research and further identify the characteristics of the middle region of relevance or partial relevance as: (1) partially relevant items may play an important role in the early stages of a user's information seeking process over time for a particular information problem and (2) a relationship may exist between partially relevant items retrieved and changes in users' information problems during an information seeking process. Results also suggest that partially relevant items may be useful at the early stages of users' information seeking processes. We propose a useful concept of relevance as a relationship and an effect on the movement of a user through the iterative stages of their information seeking process. Users' relevance judgments can also be plotted on a three-dimensional spatial model of relevance level, region and time. Implications for the development of IR systems, searching practice and relevance research are also discussed.

A three-dimensional spatial model of plutonium in soil near Rocky Flats, Colorado.

The horizontal and depth distribution of plutonium was measured in soil east of the Rocky Flats Environmental Technology Site (formerly the Rocky Flats Plant) near Denver, Colorado, during 1992-1994. The study area was centered on the eastern plume of plutonium contamination and included transects extending from 0.2 km east of the primary origin of the contamination (the 903 Pad) to distances of up to 19 km northeast, east, southeast and south-southeast of the 903 Pad. Soil was collected in 3 cm layers down to 21 cm at exponentially increasing distances along the four transects. Plutonium concentrations decreased rapidly with depth, distance from the 903 Pad, and angle from due east. Depth distributions were independent of distance and angle from the 903 Pad, and our profile model can be used to adjust to a common basis, historical measurements made from sampling to different depths. Based on a total of approximately 1,400 independent measurements, mathematical functions were developed to describe the distance, directional, and depth relationships. These equations, combined with soil density and rock measurements, provided a new method to estimate the plutonium concentration or total deposition per unit area anywhere within the study area. Total deposition per unit area measurements at 50 sites provided an independent test of the model's predictive accuracy. Sampling coefficients of variation based on replicate samples at the main sampling locations averaged 33%, but ranged from 12 to 98%. The analytical measurement coefficient of variation averaged 8%. Mean 0-3 cm soil concentrations of (239,240)Pu among 10 Front Range "background" and 11 community locations near Rocky Flats were 2.1 and 2.3 Bq kg(-1), respectively.

Acoustic radiation prediction of a compressor housing from three-dimensional experimental spatial dynamics modeling

An application of experimental spatial dynamics modeling (ESDM) is demonstrated for predicting the sound radiation from a vibrating structure based on experimental velocity response data. A scanning laser Doppler vibrometer (LDV) is used to measure velocity at thousands of locations on the surface of the radiating structure. Velocity measurements are acquired from multiple laser positions where the position and orientation of the LDV relative to the structure are determined. A weighted least-squares discrete finite element formulation is used to solve for the complex-valued continuous three-dimensional velocity response field on the surface of the structure from the experimental data for a single frequency. The velocity field solution on the surface provides the necessary boundary values input into a finite element/boundary element acoustic code for predicting acoustic radiation. This experimental-numerical noise prediction technique was demonstrated on the housing of an operational reciprocating Freon compressor. The technique was verified by comparing measured and predicted acoustic responses. This is the first time an experimental three-dimensional spatial dynamics model has been linked directly to the acoustic analysis of complex structures. The capability to make in-the-field vibration measurements, solve for the complex-valued continuous three-dimensional velocity response field, and predict the acoustic response from the same test is a novel approach and a major contribution of this work.

Perceptual scaling of synthesized musical timbres: common dimensions, specificities, and latent subject classes.

To study the perceptual structure of musical timbre and the effects of musical training, timbral dissimilarities of synthesized instrument sounds were rated by professional musicians, amateur musicians, and nonmusicians. The data were analyzed with an extended version of the multidimensional scaling algorithm CLASCAL (Winsberg & De Soete, 1993), which estimates the number of latent classes of subjects, the coordinates of each timbre on common Euclidean dimensions, a specificity value of unique attributes for each timbre, and a separate weight for each latent class on each of the common dimensions and the set of specificities. Five latent classes were found for a three-dimensional spatial model with specificities. Common dimensions were quantified psychophysically in terms of log-rise time, spectral centroid, and degree of spectral variation. The results further suggest that musical timbres possess specific attributes not accounted for by these shared perceptual dimensions. Weight patterns indicate that perceptual salience of dimensions and specificities varied across classes. A comparison of class structure with biographical factors associated with degree of musical training and activity was not clearly related to the class structure, though musicians gave more precise and coherent judgments than did non-musicians or amateurs. The model with latent classes and specificities gave a better fit to the data and made the acoustic correlates of the common dimensions more interpretable.

Diffuse Gamma-Ray Emission in the Galactic Plane from Cosmic-Ray, Matter, and Photon Interactions

On the basis of the spatial distribution, intensity, and energy spectrum, the diffuse Galactic high-energy gamma radiation is believed to be the result of cosmic-ray interactions with matter, and to a lesser extent photons. This paper describes a model calculation of diffuse gamma-ray emission based on these interactions. Recent radio observations of the main interstellar components of matter on a scale of 0.°5 are used for the entire region within 10° of the Galactic plane. A three-dimensional spatial model of the Galaxy is used to compute the emission from each volume element based on the matter, cosmic ray, and photon densities using well know interaction processes

The development of three-dimensional spatial modeling techniques for the construction planning of nuclear power plants

The results are presented of the first phase of a research project on the application of spatial modeling techniques to the process of planning and executing the construction of a nuclear power plant. A computer modeling technique, based on sets of polyhedra and spatial operations, was developed and applied to modeling the components of a nuclear power plant. The objectives of the modeling are: to store and retrieve information about the various systems in the facility; to produce drawings of those systems from any angle in differing amounts of detail; to aid in the search for interference among the parts of the plant by identifying those elements that occupy the same space or are too close to each other; to calculate information such as surface area, length, and volume of selected elements of the plant; and to aid in finding the optimum construction sequence by simulated construction of selected areas of the plant. Computer techniques are described for inputting information by digitizing directly from engineering drawings, for editing the spatial model, for management of the spatial and non-spatial data, and for graphic output from the model. The software is implemented on the University's central time-sharing computer system and on a mini-computer system in the Architectural Research Laboratory.