Topology based methods for vector field comparisons
NASA Astrophysics Data System (ADS)
Batra, Rajesh Kumar
Vector fields are commonly found in almost all branches of the physical sciences. Aerodynamics, dynamical systems, electromagnetism, and global climate modeling are a few examples. These multivariate data fields are often large, and no general, automated method exists for comparing these fields. Existing methods require either subjective visual judgments, or data interface compatibility, or domain specific knowledge. A topology based method intrinsically eliminates all of the above limitations and has the additional advantage of significantly compressing the vector field by representing only key features of the flow. Therefore, large databases are compactly represented and quickly searched. Topology is a natural framework for the study of many vector fields. It provides rules of an organizing principle, a flow grammar, that can describe and connect together the properties common to flows. Helman and Hesselink first introduced automated methods to extract and visualize this grammar. This work extends their method by introducing automated methods for vector topology comparison. Basic two-dimensional flows are first compared. The theory is extended to compare three-dimensional flow fields and the topology on no-slip surfaces. Concepts from graph theory and linear programming are utilized to solve these problems. Finally, the first automated method for higher order singularity comparisons is introduced using mathematical theories from geometric (Clifford) algebra.
DO TIE LABORATORY BASED ASSESSMENT METHODS REALLY PREDICT FIELD EFFECTS?
Sediment Toxicity Identification and Evaluation (TIE) methods have been developed for both porewaters and whole sediments. These relatively simple laboratory methods are designed to identify specific toxicants or classes of toxicants in sediments; however, the question of whethe...
DO TIE LABORATORY BASED METHODS REALLY REFLECT FIELD CONDITIONS
Sediment Toxicity Identification and Evaluation (TIE) methods have been developed for both interstitial waters and whole sediments. These relatively simple laboratory methods are designed to identify specific toxicants or classes of toxicants in sediments; however, the question ...
A novel force field parameter optimization method based on LSSVR for ECEPP.
Liu, Yunling; Tao, Lan; Lu, Jianjun; Xu, Shuo; Ma, Qin; Duan, Qingling
2011-03-23
In this paper, we propose a novel force field parameter optimization method based on LSSVR and optimize the torsion energy parameters of ECEPP force field. In this method force field parameter optimization problem is turned into a support vector regression problem. Protein samples for regression model training are chosen from Protein Data Bank. The experiments show that the optimized force-field parameters make both α-helix and β-hairpin structures more consistent with the experimental implications than the original parameters.
Vector-based plane-wave spectrum method for the propagation of cylindrical electromagnetic fields.
Shi, S; Prather, D W
1999-11-01
We present a vector-based plane-wave spectrum (VPWS) method for efficient propagation of cylindrical electromagnetic fields. In comparison with electromagnetic propagation integrals, the VPWS method significantly reduces time of propagation. Numerical results that illustrate the utility of this method are presented.
Bi, Chuan-Xing; Chen, Xin-Zhao; Chen, Jian
2008-03-01
A technique for separating sound fields using two closely spaced parallel measurement surfaces and based on equivalent source method is proposed. The method can separate wave components crossing two measurement surfaces in opposite directions, which makes nearfield acoustic holography (NAH) applications in a field where there exist sources on the two sides of the hologram surface, in a reverberant field or in a scattered field, possible. The method is flexible in applications, simple in computation, and very easy to implement. The measurement surfaces can be arbitrarily shaped, and they are not restricted to be regular as in the traditional field separation technique. And, because the method performs field separation calculations directly in the spatial domain-not in the wave number domain--it avoids the errors and limitations (the window effects, etc.) associated with the traditional field separation technique based on the spatial Fourier transform method. In the paper, a theoretical description is first given, and the performance of the proposed field separation technique and its application in NAH are then evaluated through experiments.
A new gradient shimming method based on undistorted field map of B0 inhomogeneity
NASA Astrophysics Data System (ADS)
Bao, Qingjia; Chen, Fang; Chen, Li; Song, Kan; Liu, Zao; Liu, Chaoyang
2016-04-01
Most existing gradient shimming methods for NMR spectrometers estimate field maps that resolve B0 inhomogeneity spatially from dual gradient-echo (GRE) images acquired at different echo times. However, the distortions induced by B0 inhomogeneity that always exists in the GRE images can result in estimated field maps that are distorted in both geometry and intensity, leading to inaccurate shimming. This work proposes a new gradient shimming method based on undistorted field map of B0 inhomogeneity obtained by a more accurate field map estimation technique. Compared to the traditional field map estimation method, this new method exploits both the positive and negative polarities of the frequency encoded gradients to eliminate the distortions caused by B0 inhomogeneity in the field map. Next, the corresponding automatic post-data procedure is introduced to obtain undistorted B0 field map based on knowledge of the invariant characteristics of the B0 inhomogeneity and the variant polarity of the encoded gradient. The experimental results on both simulated and real gradient shimming tests demonstrate the high performance of this new method.
A comparison of field-based similarity searching methods: CatShape, FBSS, and ROCS.
Moffat, Kirstin; Gillet, Valerie J; Whittle, Martin; Bravi, Gianpaolo; Leach, Andrew R
2008-04-01
Three field-based similarity methods are compared in retrospective virtual screening experiments. The methods are the CatShape module of CATALYST, ROCS, and an in-house program developed at the University of Sheffield called FBSS. The programs are used in both rigid and flexible searches carried out in the MDL Drug Data Report. UNITY 2D fingerprints are also used to provide a comparison with a more traditional approach to similarity searching, and similarity based on simple whole-molecule properties is used to provide a baseline for the more sophisticated searches. Overall, UNITY 2D fingerprints and ROCS with the chemical force field option gave comparable performance and were superior to the shape-only 3D methods. When the flexible methods were compared with the rigid methods, it was generally found that the flexible methods gave slightly better results than their respective rigid methods; however, the increased performance did not justify the additional computational cost required.
Zhang, Yong-Bin; Jacobsen, Finn; Bi, Chuan-Xing; Chen, Xin-Zhao
2009-09-01
The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has recently been demonstrated. This paper examines whether there might be a similar advantage in using the particle velocity as the input of NAH based on the equivalent source method (ESM). Error sensitivity considerations indicate that ESM-based NAH is less sensitive to measurement errors when it is based on particle velocity input data than when it is based on measurements of sound pressure data, and this is confirmed by a simulation study and by experimental results. A method that combines pressure- and particle velocity-based reconstructions in order to distinguish between contributions to the sound field generated by sources on the two sides of the hologram plane is also examined.
FLASHFLOOD: a 3D field-based similarity search and alignment method for flexible molecules.
Pitman, M C; Huber, W K; Horn, H; Krämer, A; Rice, J E; Swope, W C
2001-07-01
A three-dimensional field-based similarity search and alignment method for flexible molecules is introduced. The conformational space of a flexible molecule is represented in terms of fragments and torsional angles of allowed conformations. A user-definable property field is used to compute features of fragment pairs. Features are generalizations of CoMMA descriptors that characterize local regions of the property field by its local moments. The features are invariant under coordinate system transformations. Features taken from a query molecule are used to form alignments with fragment pairs in the database. An assembly algorithm is then used to merge the fragment pairs into full structures, aligned to the query. Key to the method is the use of a context adaptive descriptor scaling procedure as the basis for similarity. This allows the user to tune the weights of the various feature components based on examples relevant to the particular context under investigation. The property fields may range from simple, phenomenological fields, to fields derived from quantum mechanical calculations. We apply the method to the dihydrofolate/methotrexate benchmark system, and show that when one injects relevant contextual information into the descriptor scaling procedure, better results are obtained more efficiently. We also show how the method works and include computer times for a query from a database that represents approximately 23 million conformers of seventeen flexible molecules.
Bringing the Reality of Science Teaching by Using a Field-Based Methods Course.
ERIC Educational Resources Information Center
Hairston, Rosalina V.
This study investigates the impact of a field-based methods course on the reality of teaching experienced by preservice biology teachers. Four questions guided the research: (1) What are the perceptions of the preservice teachers about biology teaching? (2) What are the preconceptions of preservice teachers about high school students? (3) What…
Systems and Methods for Implementing Robust Carbon Nanotube-Based Field Emitters
NASA Technical Reports Server (NTRS)
Manohara, Harish (Inventor); Kristof, Valerie (Inventor); Toda, Risaku (Inventor)
2015-01-01
Systems and methods in accordance with embodiments of the invention implement carbon nanotube-based field emitters. In one embodiment, a method of fabricating a carbon nanotube field emitter includes: patterning a substrate with a catalyst, where the substrate has thereon disposed a diffusion barrier layer; growing a plurality of carbon nanotubes on at least a portion of the patterned catalyst; and heating the substrate to an extent where it begins to soften such that at least a portion of at least one carbon nanotube becomes enveloped by the softened substrate.
Error analysis for satellite gravity field determination based on two-dimensional Fourier methods
NASA Astrophysics Data System (ADS)
Cai, L.; Zhou, Z.; Hsu, H.; Gao, F.; Zhu, Z.; Luo, J.
2012-12-01
The time-wise and space-wise approaches are generally applied to data processing and error analysis for satellite gravimetry missions. But both the approaches, which are based on least-squares method, address the whole effect of measurement errors and estimate the resolution of gravity field models mainly from a numerical point of view. Moreover, requirement for higher accuracy and resolution gravity field models could make the computation more difficult, and serious numerical instabilities arise. In order to overcome the problems, this study focuses on constructing a direct relationship between power spectral density of the satellite gravimetry measurements and spherical harmonic coefficients of the Earth's gravity model. Based on two-dimensional Fourier transform, the relationship is analytically concluded. This method provides a deep physical insight into the relation between mission parameters, instrumental parameters and gravity field parameters. In contrast, the least-squares method is mainly based on a mathematical viewpoint. By taking advantage of the analytical expression, it is efficient and distinct for parameter estimation and error analysis of missions. From the relationship and the simulations, it is analytically confirmed that the low-frequency noise affects the gravity field recovery in all degrees for the instance of satellite gradiometer recovery mission. Furthermore, some other results and suggestions are also described.
Design method for a distributed Bragg resonator based evanescent field sensor
NASA Astrophysics Data System (ADS)
Bischof, David; Kehl, Florian; Michler, Markus
2016-12-01
This paper presents an analytic design method for a distributed Bragg resonator based evanescent field sensor. Such sensors can, for example, be used to measure changing refractive indices of the cover medium of a waveguide, as well as molecule adsorption at the sensor surface. For given starting conditions, the presented design method allows the analytical calculation of optimized sensor parameters for quantitative simulation and fabrication. The design process is based on the Fabry-Pérot resonator and analytical solutions of coupled mode theory.
FGG-NUFFT-Based Method for Near-Field 3-D Imaging Using Millimeter Waves
Kan, Yingzhi; Zhu, Yongfeng; Tang, Liang; Fu, Qiang; Pei, Hucheng
2016-01-01
In this paper, to deal with the concealed target detection problem, an accurate and efficient algorithm for near-field millimeter wave three-dimensional (3-D) imaging is proposed that uses a two-dimensional (2-D) plane antenna array. First, a two-dimensional fast Fourier transform (FFT) is performed on the scattered data along the antenna array plane. Then, a phase shift is performed to compensate for the spherical wave effect. Finally, fast Gaussian gridding based nonuniform FFT (FGG-NUFFT) combined with 2-D inverse FFT (IFFT) is performed on the nonuniform 3-D spatial spectrum in the frequency wavenumber domain to achieve 3-D imaging. The conventional method for near-field 3-D imaging uses Stolt interpolation to obtain uniform spatial spectrum samples and performs 3-D IFFT to reconstruct a 3-D image. Compared with the conventional method, our FGG-NUFFT based method is comparable in both efficiency and accuracy in the full sampled case and can obtain more accurate images with less clutter and fewer noisy artifacts in the down-sampled case, which are good properties for practical applications. Both simulation and experimental results demonstrate that the FGG-NUFFT-based near-field 3-D imaging algorithm can have better imaging performance than the conventional method for down-sampled measurements. PMID:27657066
Time-domain incident-field extrapolation technique based on the singularity-expansion method
Klaasen, J.J.
1991-05-01
In this report, a method presented to extrapolate measurements from Nuclear Electromagnetic Pulse (NEMP) assessments directly in the time domain. This method is based on a time-domain extrapolation function which is obtained from the Singularity Expansion Method representation of the measured incident field of the NEMP simulator. Once the time-domain extrapolation function is determined, the responses recorded during an assessment can be extrapolated simply by convolving them with the time domain extrapolation function. It is found that to obtain useful extrapolated responses, the incident field measurements needs to be made minimum phase; otherwise unbounded results can be obtained. Results obtained with this technique are presented, using data from actual assessments.
Inoue, S.; Magara, T.; Choe, G. S.; Kim, K. S.; Pandey, V. S.; Shiota, D.; Kusano, K.
2014-01-01
We develop a nonlinear force-free field (NLFFF) extrapolation code based on the magnetohydrodynamic (MHD) relaxation method. We extend the classical MHD relaxation method in two important ways. First, we introduce an algorithm initially proposed by Dedner et al. to effectively clean the numerical errors associated with ∇ · B . Second, the multigrid type method is implemented in our NLFFF to perform direct analysis of the high-resolution magnetogram data. As a result of these two implementations, we successfully extrapolated the high resolution force-free field introduced by Low and Lou with better accuracy in a drastically shorter time. We also applied our extrapolation method to the MHD solution obtained from the flux-emergence simulation by Magara. We found that NLFFF extrapolation may be less effective for reproducing areas higher than a half-domain, where some magnetic loops are found in a state of continuous upward expansion. However, an inverse S-shaped structure consisting of the sheared and twisted loops formed in the lower region can be captured well through our NLFFF extrapolation method. We further discuss how well these sheared and twisted fields are reconstructed by estimating the magnetic topology and twist quantitatively.
Spatial sound field synthesis and upmixing based on the equivalent source method.
Bai, Mingsian R; Hsu, Hoshen; Wen, Jheng-Ciang
2014-01-01
Given scarce number of recorded signals, spatial sound field synthesis with an extended sweet spot is a challenging problem in acoustic array signal processing. To address the problem, a synthesis and upmixing approach inspired by the equivalent source method (ESM) is proposed. The synthesis procedure is based on the pressure signals recorded by a microphone array and requires no source model. The array geometry can also be arbitrary. Four upmixing strategies are adopted to enhance the resolution of the reproduced sound field when there are more channels of loudspeakers than the microphones. Multi-channel inverse filtering with regularization is exploited to deal with the ill-posedness in the reconstruction process. The distance between the microphone and loudspeaker arrays is optimized to achieve the best synthesis quality. To validate the proposed system, numerical simulations and subjective listening experiments are performed. The results demonstrated that all upmixing methods improved the quality of reproduced target sound field over the original reproduction. In particular, the underdetermined ESM interpolation method yielded the best spatial sound field synthesis in terms of the reproduction error, timbral quality, and spatial quality.
A novel autonomous real-time position method based on polarized light and geomagnetic field.
Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen
2015-01-01
Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance. PMID:25851793
A novel autonomous real-time position method based on polarized light and geomagnetic field
Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen
2015-01-01
Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance. PMID:25851793
A novel autonomous real-time position method based on polarized light and geomagnetic field.
Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen
2015-04-08
Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance.
A novel autonomous real-time position method based on polarized light and geomagnetic field
NASA Astrophysics Data System (ADS)
Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Wang, Lu; Wang, Zhiwen
2015-04-01
Many animals exploit polarized light in order to calibrate their magnetic compasses for navigation. For example, some birds are equipped with biological magnetic and celestial compasses enabling them to migrate between the Western and Eastern Hemispheres. The Vikings' ability to derive true direction from polarized light is also widely accepted. However, their amazing navigational capabilities are still not completely clear. Inspired by birds' and Vikings' ancient navigational skills. Here we present a combined real-time position method based on the use of polarized light and geomagnetic field. The new method works independently of any artificial signal source with no accumulation of errors and can obtain the position and the orientation directly. The novel device simply consists of two polarized light sensors, a 3-axis compass and a computer. The field experiments demonstrate device performance.
Identifying protein interaction subnetworks by a bagging Markov random field-based method.
Chen, Li; Xuan, Jianhua; Riggins, Rebecca B; Wang, Yue; Clarke, Robert
2013-01-01
Identification of differentially expressed subnetworks from protein-protein interaction (PPI) networks has become increasingly important to our global understanding of the molecular mechanisms that drive cancer. Several methods have been proposed for PPI subnetwork identification, but the dependency among network member genes is not explicitly considered, leaving many important hub genes largely unidentified. We present a new method, based on a bagging Markov random field (BMRF) framework, to improve subnetwork identification for mechanistic studies of breast cancer. The method follows a maximum a posteriori principle to form a novel network score that explicitly considers pairwise gene interactions in PPI networks, and it searches for subnetworks with maximal network scores. To improve their robustness across data sets, a bagging scheme based on bootstrapping samples is implemented to statistically select high confidence subnetworks. We first compared the BMRF-based method with existing methods on simulation data to demonstrate its improved performance. We then applied our method to breast cancer data to identify PPI subnetworks associated with breast cancer progression and/or tamoxifen resistance. The experimental results show that not only an improved prediction performance can be achieved by the BMRF approach when tested on independent data sets, but biologically meaningful subnetworks can also be revealed that are relevant to breast cancer and tamoxifen resistance.
A Novel Microaneurysms Detection Method Based on Local Applying of Markov Random Field.
Ganjee, Razieh; Azmi, Reza; Moghadam, Mohsen Ebrahimi
2016-03-01
Diabetic Retinopathy (DR) is one of the most common complications of long-term diabetes. It is a progressive disease and by damaging retina, it finally results in blindness of patients. Since Microaneurysms (MAs) appear as a first sign of DR in retina, early detection of this lesion is an essential step in automatic detection of DR. In this paper, a new MAs detection method is presented. The proposed approach consists of two main steps. In the first step, the MA candidates are detected based on local applying of Markov random field model (MRF). In the second step, these candidate regions are categorized to identify the correct MAs using 23 features based on shape, intensity and Gaussian distribution of MAs intensity. The proposed method is evaluated on DIARETDB1 which is a standard and publicly available database in this field. Evaluation of the proposed method on this database resulted in the average sensitivity of 0.82 for a confidence level of 75 as a ground truth. The results show that our method is able to detect the low contrast MAs with the background while its performance is still comparable to other state of the art approaches.
Classification method for disease risk mapping based on discrete hidden Markov random fields.
Charras-Garrido, Myriam; Abrial, David; Goër, Jocelyn De; Dachian, Sergueï; Peyrard, Nathalie
2012-04-01
Risk mapping in epidemiology enables areas with a low or high risk of disease contamination to be localized and provides a measure of risk differences between these regions. Risk mapping models for pooled data currently used by epidemiologists focus on the estimated risk for each geographical unit. They are based on a Poisson log-linear mixed model with a latent intrinsic continuous hidden Markov random field (HMRF) generally corresponding to a Gaussian autoregressive spatial smoothing. Risk classification, which is necessary to draw clearly delimited risk zones (in which protection measures may be applied), generally must be performed separately. We propose a method for direct classified risk mapping based on a Poisson log-linear mixed model with a latent discrete HMRF. The discrete hidden field (HF) corresponds to the assignment of each spatial unit to a risk class. The risk values attached to the classes are parameters and are estimated. When mapping risk using HMRFs, the conditional distribution of the observed field is modeled with a Poisson rather than a Gaussian distribution as in image segmentation. Moreover, abrupt changes in risk levels are rare in disease maps. The spatial hidden model should favor smoothed out risks, but conventional discrete Markov random fields (e.g. the Potts model) do not impose this. We therefore propose new potential functions for the HF that take into account class ordering. We use a Monte Carlo version of the expectation-maximization algorithm to estimate parameters and determine risk classes. We illustrate the method's behavior on simulated and real data sets. Our method appears particularly well adapted to localize high-risk regions and estimate the corresponding risk levels.
NASA Astrophysics Data System (ADS)
Wen-Yu, Luo; Xiao-Lin, Yu; Xue-Feng, Yang; Ren-He, Zhang
2016-04-01
An exact solution based on the wavenumber integration method is proposed and implemented in a numerical model for the acoustic field in a Pekeris waveguide excited by either a point source in cylindrical geometry or a line source in plane geometry. Besides, an unconditionally stable numerical solution is also presented, which entirely resolves the stability problem in previous methods. Generally the branch line integral contributes to the total field only at short ranges, and hence is usually ignored in traditional normal mode models. However, for the special case where a mode lies near the branch cut, the branch line integral can contribute to the total field significantly at all ranges. The wavenumber integration method is well-suited for such problems. Numerical results are also provided, which show that the present model can serve as a benchmark for sound propagation in a Pekeris waveguide. Project supported by the National Natural Science Foundation of China (Grant No. 11125420), the Knowledge Innovation Program of the Chinese Academy of Sciences, the China Postdoctoral Science Foundation (Grant No. 2014M561882), and the Doctoral Fund of Shandong Province, China (Grant No. BS2012HZ015).
A descriptive geometry based method for total and common cameras fields of view optimization
NASA Astrophysics Data System (ADS)
Salmane, H.; Ruichek, Y.; Khoudour, L.
2011-07-01
The presented work is conducted in the framework of the ANR-VTT PANsafer project (Towards a safer level crossing). One of the objectives of the project is to develop a video surveillance system that will be able to detect and recognize potential dangerous situation around level crossings. This paper addresses the problem of cameras positioning and orientation in order to view optimally monitored scenes. In general, adjusting cameras position and orientation is achieved experimentally and empirically by considering geometrical different configurations. This step requires a lot of time to adjust approximately the total and common fields of view of the cameras, especially when constrained environments, like level crossing environments, are considered. In order to simplify this task and to get more precise cameras positioning and orientation, we propose in this paper a method that optimizes automatically the total and common cameras fields with respect to the desired scene. Based on descriptive geometry, the method estimates the best cameras position and orientation by optimizing surfaces of 2D domains that are obtained by projecting/intersecting the field of view of each camera on/with horizontal and vertical planes. The proposed method is evaluated and tested to demonstrate its effectiveness.
Zhou, Jingyu; Tian, Shulin; Yang, Chenglin
2014-01-01
Few researches pay attention to prediction about analog circuits. The few methods lack the correlation with circuit analysis during extracting and calculating features so that FI (fault indicator) calculation often lack rationality, thus affecting prognostic performance. To solve the above problem, this paper proposes a novel prediction method about single components of analog circuits based on complex field modeling. Aiming at the feature that faults of single components hold the largest number in analog circuits, the method starts with circuit structure, analyzes transfer function of circuits, and implements complex field modeling. Then, by an established parameter scanning model related to complex field, it analyzes the relationship between parameter variation and degeneration of single components in the model in order to obtain a more reasonable FI feature set via calculation. According to the obtained FI feature set, it establishes a novel model about degeneration trend of analog circuits' single components. At last, it uses particle filter (PF) to update parameters for the model and predicts remaining useful performance (RUP) of analog circuits' single components. Since calculation about the FI feature set is more reasonable, accuracy of prediction is improved to some extent. Finally, the foregoing conclusions are verified by experiments. PMID:25147853
Data collection method for mobile sensor networks based on the theory of thermal fields.
Macuha, Martin; Tariq, Muhammad; Sato, Takuro
2011-01-01
Many sensor applications are aimed for mobile objects, where conventional routing approaches of data delivery might fail. Such applications are habitat monitoring, human probes or vehicular sensing systems. This paper targets such applications and proposes lightweight proactive distributed data collection scheme for Mobile Sensor Networks (MSN) based on the theory of thermal fields. By proper mapping, we create distribution function which allows considering characteristics of a sensor node. We show the functionality of our proposed forwarding method when adapted to the energy of sensor node. We also propose enhancement in order to maximize lifetime of the sensor nodes. We thoroughly evaluate proposed solution and discuss the tradeoffs. PMID:22164011
A new method for direction finding based on Markov random field model
NASA Astrophysics Data System (ADS)
Ota, Mamoru; Kasahara, Yoshiya; Goto, Yoshitaka
2015-07-01
Investigating the characteristics of plasma waves observed by scientific satellites in the Earth's plasmasphere/magnetosphere is effective for understanding the mechanisms for generating waves and the plasma environment that influences wave generation and propagation. In particular, finding the propagation directions of waves is important for understanding mechanisms of VLF/ELF waves. To find these directions, the wave distribution function (WDF) method has been proposed. This method is based on the idea that observed signals consist of a number of elementary plane waves that define wave energy density distribution. However, the resulting equations constitute an ill-posed problem in which a solution is not determined uniquely; hence, an adequate model must be assumed for a solution. Although many models have been proposed, we have to select the most optimum model for the given situation because each model has its own advantages and disadvantages. In the present study, we propose a new method for direction finding of the plasma waves measured by plasma wave receivers. Our method is based on the assumption that the WDF can be represented by a Markov random field model with inference of model parameters performed using a variational Bayesian learning algorithm. Using computer-generated spectral matrices, we evaluated the performance of the model and compared the results with those obtained from two conventional methods.
Electrolocation-based underwater obstacle avoidance using wide-field integration methods.
Dimble, Kedar D; Faddy, James M; Humbert, J Sean
2014-03-01
Weakly electric fish are capable of efficiently performing obstacle avoidance in dark and navigationally challenging aquatic environments using electrosensory information. This sensory modality enables extraction of relevant proximity information about surrounding obstacles by interpretation of perturbations induced to the fish's self-generated electric field. In this paper, reflexive obstacle avoidance is demonstrated by extracting relative proximity information using spatial decompositions of the perturbation signal, also called an electric image. Electrostatics equations were formulated for mathematically expressing electric images due to a straight tunnel to the electric field generated with a planar electro-sensor model. These equations were further used to design a wide-field integration based static output feedback controller. The controller was implemented in quasi-static simulations for environments with complicated geometries modelled using finite element methods to demonstrate sense and avoid behaviours. The simulation results were confirmed by performing experiments using a computer operated gantry system in environments lined with either conductive or non-conductive objects acting as global stimuli to the field of the electro-sensor. The proposed approach is computationally inexpensive and readily implementable, making underwater autonomous navigation in real-time feasible.
Using geotypes for landslide hazard assessment and mapping: a coupled field and GIS-based method
NASA Astrophysics Data System (ADS)
Bilgot, S.; Parriaux, A.
2009-04-01
Switzerland is exceptionally subjected to landslides; indeed, about 10% of its area is considered as unstable. Making this observation, its Department of the Environment (BAFU) introduces in 1997 a method to realize landslide hazard maps. It is routinely used but, like most of the methods applied in Europe to map unstable areas, it is mainly based on the signs of previous or current phenomena (geomorphologic mapping, archive consultation, etc.) even though instabilities can appear where there is nothing to show that they existed earlier. Furthermore, the transcription from the geomorphologic map to the hazard map can vary according to the geologist or the geographer who realizes it: this method is affected by a certain lack of transparency. The aim of this project is to introduce the bedrock of a new method for landslide hazard mapping; based on instability predisposition assessment, it involves the designation of main factors for landslide susceptibility, their integration in a GIS to calculate a landslide predisposition index and the implementation of new methods to evaluate these factors; to be competitive, these processes have to be both cheap and quick. To identify the most important parameters to consider for assessing slope stability, we chose a large panel of topographic, geomechanic and hydraulic parameters and tested their importance by calculating safety factors on theoretical landslides using Geostudio 2007®; thus, we could determine that slope, cohesion, hydraulic conductivity and saturation play an important role in soil stability. After showing that cohesion and hydraulic conductivity of loose materials are strongly linked to their granulometry and plasticity index, we implemented two new field tests, one based on teledetection and one coupled sedimentometric and blue methylen test to evaluate these parameters. From these data, we could deduce approximated values of maximum cohesion and saturated hydraulic conductivity. The hydraulic conductivity of
A Five-Parameter Wind Field Estimation Method Based on Spherical Upwind Lidar Measurements
NASA Astrophysics Data System (ADS)
Kapp, S.; Kühn, M.
2014-12-01
Turbine mounted scanning lidar systems of focussed continuous-wave type are taken into consideration to sense approaching wind fields. The quality of wind information depends on the lidar technology itself but also substantially on the scanning technique and reconstruction algorithm. In this paper a five-parameter wind field model comprising mean wind speed, vertical and horizontal linear shear and homogeneous direction angles is introduced. A corresponding parameter estimation method is developed based on the assumption of upwind lidar measurements scanned over spherical segments. As a main advantage of this method all relevant parameters, in terms of wind turbine control, can be provided. Moreover, the ability to distinguish between shear and skew potentially increases the quality of the resulting feedforward pitch angles when compared to three-parameter methods. It is shown that minimal three measurements, each in turn from two independent directions are necessary for the application of the algorithm, whereas simpler measurements, each taken from only one direction, are not sufficient.
Using geotypes for landslide hazard assessment and mapping: a coupled field and GIS-based method
NASA Astrophysics Data System (ADS)
Bilgot, S.; Parriaux, A.
2009-04-01
Switzerland is exceptionally subjected to landslides; indeed, about 10% of its area is considered as unstable. Making this observation, its Department of the Environment (BAFU) introduces in 1997 a method to realize landslide hazard maps. It is routinely used but, like most of the methods applied in Europe to map unstable areas, it is mainly based on the signs of previous or current phenomena (geomorphologic mapping, archive consultation, etc.) even though instabilities can appear where there is nothing to show that they existed earlier. Furthermore, the transcription from the geomorphologic map to the hazard map can vary according to the geologist or the geographer who realizes it: this method is affected by a certain lack of transparency. The aim of this project is to introduce the bedrock of a new method for landslide hazard mapping; based on instability predisposition assessment, it involves the designation of main factors for landslide susceptibility, their integration in a GIS to calculate a landslide predisposition index and the implementation of new methods to evaluate these factors; to be competitive, these processes have to be both cheap and quick. To identify the most important parameters to consider for assessing slope stability, we chose a large panel of topographic, geomechanic and hydraulic parameters and tested their importance by calculating safety factors on theoretical landslides using Geostudio 2007®; thus, we could determine that slope, cohesion, hydraulic conductivity and saturation play an important role in soil stability. After showing that cohesion and hydraulic conductivity of loose materials are strongly linked to their granulometry and plasticity index, we implemented two new field tests, one based on teledetection and one coupled sedimentometric and blue methylen test to evaluate these parameters. From these data, we could deduce approximated values of maximum cohesion and saturated hydraulic conductivity. The hydraulic conductivity of
Schall, Mark C; Fethke, Nathan B; Chen, Howard; Gerr, Fred
2015-05-01
The performance of an inertial measurement unit (IMU) system for directly measuring thoracolumbar trunk motion was compared to that of the Lumbar Motion Monitor (LMM). Thirty-six male participants completed a simulated material handling task with both systems deployed simultaneously. Estimates of thoracolumbar trunk motion obtained with the IMU system were processed using five common methods for estimating trunk motion characteristics. Results of measurements obtained from IMUs secured to the sternum and pelvis had smaller root-mean-square differences and mean bias estimates in comparison to results obtained with the LMM than results of measurements obtained solely from a sternum mounted IMU. Fusion of IMU accelerometer measurements with IMU gyroscope and/or magnetometer measurements was observed to increase comparability to the LMM. Results suggest investigators should consider computing thoracolumbar trunk motion as a function of estimates from multiple IMUs using fusion algorithms rather than using a single accelerometer secured to the sternum in field-based studies.
NASA Astrophysics Data System (ADS)
Diaz, P. M. A.; Feitosa, R. Q.; Sanches, I. D.; Costa, G. A. O. P.
2016-06-01
This paper presents a method to estimate the temporal interaction in a Conditional Random Field (CRF) based approach for crop recognition from multitemporal remote sensing image sequences. This approach models the phenology of different crop types as a CRF. Interaction potentials are assumed to depend only on the class labels of an image site at two consecutive epochs. In the proposed method, the estimation of temporal interaction parameters is considered as an optimization problem, whose goal is to find the transition matrix that maximizes the CRF performance, upon a set of labelled data. The objective functions underlying the optimization procedure can be formulated in terms of different accuracy metrics, such as overall and average class accuracy per crop or phenological stages. To validate the proposed approach, experiments were carried out upon a dataset consisting of 12 co-registered LANDSAT images of a region in southeast of Brazil. Pattern Search was used as the optimization algorithm. The experimental results demonstrated that the proposed method was able to substantially outperform estimates related to joint or conditional class transition probabilities, which rely on training samples.
Study on Two Methods for Nonlinear Force-Free Extrapolation Based on Semi-Analytical Field
NASA Astrophysics Data System (ADS)
Liu, S.; Zhang, H. Q.; Su, J. T.; Song, M. T.
2011-03-01
In this paper, two semi-analytical solutions of force-free fields (Low and Lou, Astrophys. J. 352, 343, 1990) have been used to test two nonlinear force-free extrapolation methods. One is the boundary integral equation (BIE) method developed by Yan and Sakurai ( Solar Phys. 195, 89, 2000), and the other is the approximate vertical integration (AVI) method developed by Song et al. ( Astrophys. J. 649, 1084, 2006). Some improvements have been made to the AVI method to avoid the singular points in the process of calculation. It is found that the correlation coefficients between the first semi-analytical field and extrapolated field using the BIE method, and also that obtained by the improved AVI method, are greater than 90% below a height 10 of the 64×64 lower boundary. For the second semi-analytical field, these correlation coefficients are greater than 80% below the same relative height. Although differences between the semi-analytical solutions and the extrapolated fields exist for both the BIE and AVI methods, these two methods can give reliable results for heights of about 15% of the extent of the lower boundary.
Zhang, Yihui; Yang, Yongying; Li, Chen; Wu, Fan; Chai, Huiting; Yan, Kai; Zhou, Lin; Li, Yang; Liu, Dong; Bai, Jian; Shen, Yibing
2016-08-10
In the field of automatic optical inspection, it is imperative to measure the defects on spherical optical surfaces. So a novel spherical surface defect evaluation system is established in this paper to evaluate defects on optical spheres. In order to ensure the microscopic scattering dark-field imaging of optical spheres with different surface shape and radius of curvature, illumination with variable aperture angle is employed. In addition, the scanning path of subapertures along the parallels and meridians is planned to detect the large optical spheres. Since analysis shows that the spherical defect information could be lost in the optical imaging, the three-dimensional correction based on a pin-hole model is proposed to recover the actual spherical defects from the captured two-dimensional images. Given the difficulty of subaperture stitching and defect feature extraction in three-dimensional (3D) space after the correction, the 3D subapertures are transformed into a plane to be spliced through geometric projection. Then, methods of the surface integral and calibration are applied to quantitatively evaluate the spherical defects. Furthermore, the 3D panorama of defect distribution on the spherical optical components can be displayed through the inverse projective reconstruction. Finally, the evaluation results are compared with the OLYMPUS microscope, testifying to the micrometer resolution, and the detection error is less than 5%. PMID:27534456
NASA Astrophysics Data System (ADS)
Ward, A. L.; Draper, K.; Hasan, N.
2010-12-01
Knowledge of spatially variable aquifer hydraulic and sorption parameters is a pre-requisite for an improved understanding of the transport and spreading of sorbing solutes and for the development of effective strategies for remediation. Local-scale estimates of these parameters are often derived from core measurements but are typically not representative of field values. Fields-scale estimates are typically derived from pump and tracer tests but often lack the spatial resolution necessary to deconvolve the effects of fine-scale heterogeneities. Geophysical methods have the potential to bridge this gap both in terms of coverage and resolution, provided meaningful petrophysical relationships can be developed. The objective of this study was to develop a petrophysical relationship between soil textural attributes and the gamma-energy response of natural sediments. Measurements from Hanford’s 300 Area show the best model to be a linear relationship between 232Th concentration and clay content (R2 = 94%). This relationship was used to generate a 3-D distribution of clay mass fraction based on borehole spectral gamma logs. The distribution of clay was then used to predict distributions of permeability, porosity, bubbling pressure, and the pore-size distribution index, all of which are required for predicting variably saturated flow, as well as the specific surface area and cation exchange capacity needed for reactive transport predictions. With this approach, it is possible to obtain reliable estimates of hydraulic properties in zones that could not be characterized by field or laboratory measurements. The spatial distribution of flow properties is consistent with lithologic transitions inferred from geologist’s logs. A preferential flow path, identified from solute and heat tracer experiments and attributed to an erosional incision in the low-permeability Ringold Formation, is also evident. The resulting distributions can be used as a starting model for the
Correlation-based methods in calibrating an FBG sensor with strain field non-uniformity
NASA Astrophysics Data System (ADS)
Cieszczyk, S.
2015-12-01
Fibre Bragg gratings have many sensing applications, mainly for measuring strain and temperature. The physical quantity that influences grating uniformly along its length causes a related shift of the Bragg wavelength. Many peak detection algorithms have been proposed, among which the most popular are the detection of maximum intensity, the centroid detection, the least square method, the cross-correlation, auto-correlation and fast phase correlation. Nonuniform gratings elongation is a cause of spectrum deformation. The introduction of non-uniformity can be intentional or appear as an unintended effect of placing sensing elements in the tested structure. Heterogeneous impacts on grating may result in additional errors and the difficulty in tracking the Bragg wavelength based on a distorted spectrum. This paper presents the application of correlation methods of peak wavelength shifts estimation for non-uniform Bragg grating elongation. The autocorrelation, cross-correlation and fast phase correlation algorithms are considered and experimental spectra measured for axisymmetric strain field along the Bragg grating are analyzed. The strain profile consists of constant and variable components. The results of this study indicate the properties of correlation algorithms applied to moderately non-uniform elongation of an FBG sensor.
The value of mindfulness-based methods in teaching at a clinical field placement.
Gökhan, Nurper; Meehan, Edward F; Peters, Kevin
2010-04-01
The value of mindfulness-based methods in an undergraduate field placement was investigated in relation to the acquisition of self-care and other basic clinical competencies. The participants were 22 students in an applied behavioral analysis course, which included a mindfulness-based training module, and 20 students enrolled in an experimental psychology course without mindfulness training. The Mindfulness Attention and Awareness Scale, the Freiberg Mindfulness Inventory, and the Kentucky Inventory of Mindfulness Skills were used as measurements before and after intervention. Mindfulness-trained participants kept records and were asked to share their personal experiences during supervision and an exit interview. Results demonstrated that training significantly increased mindfulness. Qualitative data indicated enhanced self-care, attention to well-being, self-awareness, active involvement acquiring skills, and empathy and compassion. The need to expand the utility of mindfulness to the realm of education and the importance of including comparison groups with other self-care modules for future studies were discussed.
A novel SAR fusion image segmentation method based on triplet Markov field
NASA Astrophysics Data System (ADS)
Wang, Jiajing; Jiao, Shuhong; Sun, Zhenyu
2015-03-01
Markov random field (MRF) has been widely used in SAR image segmentation because of the advantage of directly modeling the posterior distribution and suppresses the speckle on the influence of the segmentation result. However, when the real SAR images are nonstationary images, the unsupervised segmentation results by MRF can be poor. The recent proposed triplet Markov field (TMF) model is well appropriate for nonstationary SAR image processing due to the introduction of an auxiliary field which reflects the nonstationarity. In addition, on account of the texture features of SAR image, a fusion image segmentation method is proposed by fusing the gray level image and texture feature image. The effectiveness of the proposed method in this paper is demonstrated by a synthesis SAR image and the real SAR images segmentation experiments, and it is better than the state-of-art methods.
An automatic detection method to the field wheat based on image processing
NASA Astrophysics Data System (ADS)
Wang, Yu; Cao, Zhiguo; Bai, Xiaodong; Yu, Zhenghong; Li, Yanan
2013-10-01
The automatic observation of the field crop attracts more and more attention recently. The use of image processing technology instead of the existing manual observation method can observe timely and manage consistently. It is the basis that extracting the wheat from the field wheat images. In order to improve accuracy of the wheat segmentation, a novel two-stage wheat image segmentation method is proposed. Training stage adjusts several key thresholds which will be used in segmentation stage to achieve the best segmentation results, and counts these thresholds. Segmentation stage compares the different values of color index to determine which class of each pixel is. To verify the superiority of the proposed algorithm, we compared our method with other crop segmentation methods. Experiment results shows that the proposed method has the best performance.
A new resonance based method for the measurement of magnetic field intensity
NASA Astrophysics Data System (ADS)
Kaluvan, Suresh; Park, Jinhyuk; Zhang, Haifeng; Umapathy, Mangalanathan; Choi, Seung-Bok
2016-04-01
A new magnetic field intensity measurement method using resonance principle is proposed in this paper. The proposed magnetic field sensor consists of magneto rheological (MR) fluid placed between two collocated, piezo-bounded, metallic, circular disc mounted face to face in the z-axis. The resonant frequency of the disc is changed by the magnetic field dependent viscosity of the MR fluid. The key enabling concept in this work is stiffening the circular metal disc using the rheological effect of MR fluid i.e. resonant frequency varies with respect to magnetic field strength. The change in resonant frequency is measured using simple closed loop electronics connected between the two piezo crystals. The analytical model of the vibrating circular discs with MR fluid placed at the center is derived and the results are validated with experimentation. The proposed magnetic flux density measurement concept is novel and it is found to have better sensitivity and linearity.
NASA Astrophysics Data System (ADS)
Zhang, Lihui; Wang, Dongchuan; Huang, Mingxiang; Gong, Jianhua; Fang, Liqun; Cao, Wuchun
2008-10-01
With the development of mobile technologies and the integration with the spatial information technologies, it becomes possible to provide a potential to develop new techno-support solutions to Epidemiological Field Investigation especially for the disposal of emergent public health events. Based on mobile technologies and virtual geographic environment, the authors have designed a model for collaborative work in four communication patterns, namely, S2S (Static to Static), M2S (Mobile to Static), S2M (Static to Mobile), and M2M (Mobile to Mobile). Based on the model mentioned above, this paper stresses to explore mobile online mapping regarding mobile collaboration and conducts an experimental case study of HFRS (Hemorrhagic Fever with Renal Syndrome) fieldwork, and then develops a prototype system of emergent response disposition information system to test the effectiveness and usefulness of field survey based on mobile collaboration.
Zhang, Xiao-Zheng; Thomas, Jean-Hugh; Bi, Chuan-Xing; Pascal, Jean-Claude
2012-10-01
A time-domain plane wave superposition method is proposed to reconstruct nonstationary sound fields. In this method, the sound field is expressed as a superposition of time convolutions between the estimated time-wavenumber spectrum of the sound pressure on a virtual source plane and the time-domain propagation kernel at each wavenumber. By discretizing the time convolutions directly, the reconstruction can be carried out iteratively in the time domain, thus providing the advantage of continuously reconstructing time-dependent pressure signals. In the reconstruction process, the Tikhonov regularization is introduced at each time step to obtain a relevant estimate of the time-wavenumber spectrum on the virtual source plane. Because the double infinite integral of the two-dimensional spatial Fourier transform is discretized directly in the wavenumber domain in the proposed method, it does not need to perform the two-dimensional spatial fast Fourier transform that is generally used in time domain holography and real-time near-field acoustic holography, and therefore it avoids some errors associated with the two-dimensional spatial fast Fourier transform in theory and makes possible to use an irregular microphone array. The feasibility of the proposed method is demonstrated by numerical simulations and an experiment with two speakers.
Evaluation of three field-based methods for quantifying soil carbon.
Izaurralde, Roberto C; Rice, Charles W; Wielopolski, Lucian; Ebinger, Michael H; Reeves, James B; Thomson, Allison M; Harris, Ronny; Francis, Barry; Mitra, Sudeep; Rappaport, Aaron G; Etchevers, Jorge D; Sayre, Kenneth D; Govaerts, Bram; McCarty, Gregory W
2013-01-01
Three advanced technologies to measure soil carbon (C) density (g C m(-2)) are deployed in the field and the results compared against those obtained by the dry combustion (DC) method. The advanced methods are: a) Laser Induced Breakdown Spectroscopy (LIBS), b) Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS), and c) Inelastic Neutron Scattering (INS). The measurements and soil samples were acquired at Beltsville, MD, USA and at Centro International para el Mejoramiento del Maíz y el Trigo (CIMMYT) at El Batán, Mexico. At Beltsville, soil samples were extracted at three depth intervals (0-5, 5-15, and 15-30 cm) and processed for analysis in the field with the LIBS and DRIFTS instruments. The INS instrument determined soil C density to a depth of 30 cm via scanning and stationary measurements. Subsequently, soil core samples were analyzed in the laboratory for soil bulk density (kg m(-3)), C concentration (g kg(-1)) by DC, and results reported as soil C density (kg m(-2)). Results from each technique were derived independently and contributed to a blind test against results from the reference (DC) method. A similar procedure was employed at CIMMYT in Mexico employing but only with the LIBS and DRIFTS instruments. Following conversion to common units, we found that the LIBS, DRIFTS, and INS results can be compared directly with those obtained by the DC method. The first two methods and the standard DC require soil sampling and need soil bulk density information to convert soil C concentrations to soil C densities while the INS method does not require soil sampling. We conclude that, in comparison with the DC method, the three instruments (a) showed acceptable performances although further work is needed to improve calibration techniques and (b) demonstrated their portability and their capacity to perform under field conditions. PMID:23383225
Evaluation of Three Field-Based Methods for Quantifying Soil Carbon
Izaurralde, Roberto C.; Rice, Charles W.; Wielopolski, Lucien; Ebinger, Michael H.; Reeves, James B.; Thomson, Allison M.; Harris, Ron; Francis, Barry; Mitra, S.; Rappaport, Aaron; Etchevers, Jorge; Sayre, Ken D.; Govaerts, Bram; McCarty, G. W.
2013-01-31
Three advanced technologies to measure soil carbon (C) density (g C m22) are deployed in the field and the results compared against those obtained by the dry combustion (DC) method. The advanced methods are: a) Laser Induced Breakdown Spectroscopy (LIBS), b) Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS), and c) Inelastic Neutron Scattering (INS). The measurements and soil samples were acquired at Beltsville, MD, USA and at Centro International para el Mejoramiento del Maiz y el Trigo (CIMMYT) at El Bata´n, Mexico. At Beltsville, soil samples were extracted at three depth intervals (0–5, 5–15, and 15–30 cm) and processed for analysis in the field with the LIBS and DRIFTS instruments. The INS instrument determined soil C density to a depth of 30 cm via scanning and stationary measurements. Subsequently, soil core samples were analyzed in the laboratory for soil bulk density (kg m23), C concentration (g kg21) by DC, and results reported as soil C density (kg m22). Results from each technique were derived independently and contributed to a blind test against results from the reference (DC) method. A similar procedure was employed at CIMMYT in Mexico employing but only with the LIBS and DRIFTS instruments. Following conversion to common units, we found that the LIBS, DRIFTS, and INS results can be compared directly with those obtained by the DC method. The first two methods and the standard DC require soil sampling and need soil bulk density information to convert soil C concentrations to soil C densities while the INS method does not require soil sampling. We conclude that, in comparison with the DC method, the three instruments (a) showed acceptable performances although further work is needed to improve calibration techniques and (b) demonstrated their portability and their capacity to perform under field conditions.
Evaluation of Three Field-Based Methods for Quantifying Soil Carbon
Izaurralde, Roberto C.; Rice, Charles W.; Wielopolski, Lucian; Ebinger, Michael H.; Reeves, James B.; Thomson, Allison M.; Francis, Barry; Mitra, Sudeep; Rappaport, Aaron G.; Etchevers, Jorge D.; Sayre, Kenneth D.; Govaerts, Bram; McCarty, Gregory W.
2013-01-01
Three advanced technologies to measure soil carbon (C) density (g C m−2) are deployed in the field and the results compared against those obtained by the dry combustion (DC) method. The advanced methods are: a) Laser Induced Breakdown Spectroscopy (LIBS), b) Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS), and c) Inelastic Neutron Scattering (INS). The measurements and soil samples were acquired at Beltsville, MD, USA and at Centro International para el Mejoramiento del Maíz y el Trigo (CIMMYT) at El Batán, Mexico. At Beltsville, soil samples were extracted at three depth intervals (0–5, 5–15, and 15–30 cm) and processed for analysis in the field with the LIBS and DRIFTS instruments. The INS instrument determined soil C density to a depth of 30 cm via scanning and stationary measurements. Subsequently, soil core samples were analyzed in the laboratory for soil bulk density (kg m−3), C concentration (g kg−1) by DC, and results reported as soil C density (kg m−2). Results from each technique were derived independently and contributed to a blind test against results from the reference (DC) method. A similar procedure was employed at CIMMYT in Mexico employing but only with the LIBS and DRIFTS instruments. Following conversion to common units, we found that the LIBS, DRIFTS, and INS results can be compared directly with those obtained by the DC method. The first two methods and the standard DC require soil sampling and need soil bulk density information to convert soil C concentrations to soil C densities while the INS method does not require soil sampling. We conclude that, in comparison with the DC method, the three instruments (a) showed acceptable performances although further work is needed to improve calibration techniques and (b) demonstrated their portability and their capacity to perform under field conditions. PMID:23383225
Localization of incipient tip vortex cavitation using ray based matched field inversion method
NASA Astrophysics Data System (ADS)
Kim, Dongho; Seong, Woojae; Choo, Youngmin; Lee, Jeunghoon
2015-10-01
Cavitation of marine propeller is one of the main contributing factors of broadband radiated ship noise. In this research, an algorithm for the source localization of incipient vortex cavitation is suggested. Incipient cavitation is modeled as monopole type source and matched-field inversion method is applied to find the source position by comparing the spatial correlation between measured and replicated pressure fields at the receiver array. The accuracy of source localization is improved by broadband matched-field inversion technique that enhances correlation by incoherently averaging correlations of individual frequencies. Suggested localization algorithm is verified through known virtual source and model test conducted in Samsung ship model basin cavitation tunnel. It is found that suggested localization algorithm enables efficient localization of incipient tip vortex cavitation using a few pressure data measured on the outer hull above the propeller and practically applicable to the typically performed model scale experiment in a cavitation tunnel at the early design stage.
A GPU-based calculation using the three-dimensional FDTD method for electromagnetic field analysis.
Nagaoka, Tomoaki; Watanabe, Soichi
2010-01-01
Numerical simulations with the numerical human model using the finite-difference time domain (FDTD) method have recently been performed frequently in a number of fields in biomedical engineering. However, the FDTD calculation runs too slowly. We focus, therefore, on general purpose programming on the graphics processing unit (GPGPU). The three-dimensional FDTD method was implemented on the GPU using Compute Unified Device Architecture (CUDA). In this study, we used the NVIDIA Tesla C1060 as a GPGPU board. The performance of the GPU is evaluated in comparison with the performance of a conventional CPU and a vector supercomputer. The results indicate that three-dimensional FDTD calculations using a GPU can significantly reduce run time in comparison with that using a conventional CPU, even a native GPU implementation of the three-dimensional FDTD method, while the GPU/CPU speed ratio varies with the calculation domain and thread block size.
GPU-based parallel method of temperature field analysis in a floor heater with a controller
NASA Astrophysics Data System (ADS)
Forenc, Jaroslaw
2016-06-01
A parallel method enabling acceleration of the numerical analysis of the transient temperature field in an air floor heating system is presented in this paper. An initial-boundary value problem of the heater regulated by an on/off controller is formulated. The analogue model is discretized using the implicit finite difference method. The BiCGStab method is used to compute the obtained system of equations. A computer program implementing simultaneous computations on CPUand GPU(GPGPUtechnology) was developed. CUDA environment and linear algebra libraries (CUBLAS and CUSPARSE) are used by this program. The time of computations was reduced eight times in comparison with a program executed on the CPU only. Results of computations are presented in the form of time profiles and temperature field distributions. An influence of a model of the heat transfer coefficient on the simulation of the system operation was examined. The physical interpretation of obtained results is also presented.Results of computations were verified by comparing them with solutions obtained with the use of a commercial program - COMSOL Mutiphysics.
Microlens assembly error analysis for light field camera based on Monte Carlo method
NASA Astrophysics Data System (ADS)
Li, Sai; Yuan, Yuan; Zhang, Hao-Wei; Liu, Bin; Tan, He-Ping
2016-08-01
This paper describes numerical analysis of microlens assembly errors in light field cameras using the Monte Carlo method. Assuming that there were no manufacturing errors, home-built program was used to simulate images of coupling distance error, movement error and rotation error that could appear during microlens installation. By researching these images, sub-aperture images and refocus images, we found that the images present different degrees of fuzziness and deformation for different microlens assembly errors, while the subaperture image presents aliasing, obscured images and other distortions that result in unclear refocus images.
NASA Astrophysics Data System (ADS)
Sun, Xu; Yang, Lina; Gao, Lianru; Zhang, Bing; Li, Shanshan; Li, Jun
2015-01-01
Center-oriented hyperspectral image clustering methods have been widely applied to hyperspectral remote sensing image processing; however, the drawbacks are obvious, including the over-simplicity of computing models and underutilized spatial information. In recent years, some studies have been conducted trying to improve this situation. We introduce the artificial bee colony (ABC) and Markov random field (MRF) algorithms to propose an ABC-MRF-cluster model to solve the problems mentioned above. In this model, a typical ABC algorithm framework is adopted in which cluster centers and iteration conditional model algorithm's results are considered as feasible solutions and objective functions separately, and MRF is modified to be capable of dealing with the clustering problem. Finally, four datasets and two indices are used to show that the application of ABC-cluster and ABC-MRF-cluster methods could help to obtain better image accuracy than conventional methods. Specifically, the ABC-cluster method is superior when used for a higher power of spectral discrimination, whereas the ABC-MRF-cluster method can provide better results when used for an adjusted random index. In experiments on simulated images with different signal-to-noise ratios, ABC-cluster and ABC-MRF-cluster showed good stability.
Successes and challenges in a field-based, multi-method study of home telehealth.
Hebert, M A; Jansen, J J; Brant, R; Hailey, D; van der Pol, M
2004-01-01
We are conducting a three-year study of telehealth in 11 home care offices that serve rural clients in Alberta. Three hundred and twenty palliative home care clients are being recruited to participate in a randomized controlled trial (RCT) to answer three questions about the use of video-phones and their effect on symptom management, quality of life and cost, as well as readiness to use the technology. Both successes and challenges have been identified in three main areas: technology, people/organizational issues and study design. Maintaining study integrity has been the key factor in decision making, as adjustments from the original proposal are made. It is already clear that field-based RCTs are feasible, but require commitment and flexibility on the part of researchers and community partners to work through the study implementation.
Virtual local target method for avoiding local minimum in potential field based robot navigation.
Zou, Xi-Yong; Zhu, Jing
2003-01-01
A novel robot navigation algorithm with global path generation capability is presented. Local minimum is a most intractable but is an encountered frequently problem in potential field based robot navigation. Through appointing appropriately some virtual local targets on the journey, it can be solved effectively. The key concept employed in this algorithm are the rules that govern when and how to appoint these virtual local targets. When the robot finds itself in danger of local minimum, a virtual local target is appointed to replace the global goal temporarily according to the rules. After the virtual target is reached, the robot continues on its journey by heading towards the global goal. The algorithm prevents the robot from running into local minima anymore. Simulation results showed that it is very effective in complex obstacle environments. PMID:12765277
Virtual local target method for avoiding local minimum in potential field based robot navigation.
Zou, Xi-Yong; Zhu, Jing
2003-01-01
A novel robot navigation algorithm with global path generation capability is presented. Local minimum is a most intractable but is an encountered frequently problem in potential field based robot navigation. Through appointing appropriately some virtual local targets on the journey, it can be solved effectively. The key concept employed in this algorithm are the rules that govern when and how to appoint these virtual local targets. When the robot finds itself in danger of local minimum, a virtual local target is appointed to replace the global goal temporarily according to the rules. After the virtual target is reached, the robot continues on its journey by heading towards the global goal. The algorithm prevents the robot from running into local minima anymore. Simulation results showed that it is very effective in complex obstacle environments.
QMQSAR: utilization of a semiempirical probe potential in a field-based QSAR method.
Dixon, Steve; Merz, Kenneth M; Lauri, Giorgio; Ianni, James C
2005-01-15
A semiempirical quantum mechanical approach is described for the creation of molecular field-based QSAR models from a set of aligned ligand structures. Each ligand is characterized by a set of probe interaction energy (PIE) values computed at various grid points located near the surface of the ligand. Single-point PM3 calculations afford these PIE values, which represents a pool of independent variables from which multilinear regression models of activity are built. The best n-variable fit is determined by constructing an initial regression using standard forward stepwise selection, followed by refinement using a simulated annealing technique. The resulting fit provides an easily interpreted 3D physical model of ligand binding affinity. Validation against three literature datasets demonstrates the ability of the semiempirical potential to model critical binding interactions in diverse systems.
NASA Astrophysics Data System (ADS)
Ahrens, T.; Matson, P.; Lobell, D.
2006-12-01
Sensitivity analyses (SA) of biogeochemical and agricultural models are often used to identify the importance of input variables for variance in model outputs, such as crop yield or nitrate leaching. Identification of these factors can aid in prioritizing efforts in research or decision support. Many types of sensitivity analyses are available, ranging from simple One-At-A-Time (OAT) screening exercises to more complex local and global variance-based methods (see Saltelli et al 2004). The purpose of this study was to determine the influence of the type of SA on factor prioritization in the Yaqui Valley, Mexico using the Water and Nitrogen Management Model (WNMM; Chen et al 2005). WNMM, a coupled plant-growth - biogeochemistry simulation model, was calibrated to reproduce crop growth, soil moisture, and gaseous N emission dynamics in experimental plots of irrigated wheat in the Yaqui Valley, Mexico from 1994-1997. Three types of SA were carried out using 16 input variables, including parameters related to weather, soil properties and crop management. Methods used for SA were local OAT, Monte Carlo (MC), and a global variance-based method (orthogonal input; OI). Results of the SA were based on typical interpretations used for each test: maximum absolute ratio of variation (MAROV) for OAT analyses; first- and second-order regressions for MC analyses; and a total effects index for OI. The three most important factors identified by MC and OI methods were generally in agreement, although the order of importance was not always consistent and there was little agreement for variables of less importance. OAT over-estimated the importance of two factors (planting date and pH) for many outputs. The biggest differences between the OAT results and those from MC and OI were likely due to the inability of OAT methods to account for non-linearity (eg. pH and ammonia volatilization), interactions among variables (eg. pH and timing of fertilization) and an over-reliance on baseline
NASA Astrophysics Data System (ADS)
Chen, Haijun; Houkes, Zweitze
1998-09-01
In this paper, a segmentation method for agricultural fields in aerial sequences of images based on the Circular Symmetri Auto-Regressive (CSAR) model is presented. The image sequences assumed to be acquired by a video camera (RGB-CCD system) from an aeroplane, which moves linearly over the scene. The objects in the scenes being considered in this paper, are agricultural fields. The classes of agricultural fields to be distinguished are determined by the type of crop, e.g. potatoes sugar beet, wheat, etc. In order to recognize and classify these fields from aerial sequence of images, a reliable segmentatio is required. Here texture features are used for segmentation. The implementation of segmentation for agricultural fields in aerial sequences of images is based on CSAR model in texture analysis. By comparing the estimated parameters of CSAR model from different area in an image, the characteristics and the class of a texture may be determined. The paper describes the segmentation method and its evaluation through experiments. Based on segmentation results, classification for surface texture of vegetation from aerial sequences of images is realized.
Image restoration method based on Hilbert transform for full-field optical coherence tomography
NASA Astrophysics Data System (ADS)
Na, Jihoon; Choi, Woo June; Choi, Eun Seo; Ryu, Seon Young; Lee, Byeong Ha
2008-01-01
A full-field optical coherence tomography (FF-OCT) system utilizing a simple but novel image restoration method suitable for a high-speed system is demonstrated. An en-face image is retrieved from only two phase-shifted interference fringe images through using the mathematical Hilbert transform. With a thermal light source, a high-resolution FF-OCT system having axial and transverse resolutions of 1 and 2.2 μm, respectively, was implemented. The feasibility of the proposed scheme is confirmed by presenting the obtained en-face images of biological samples such as a piece of garlic and a gold beetle. The proposed method is robust to the error in the amount of the phase shift and does not leave residual fringes. The use of just two interference images and the strong immunity to phase errors provide great advantages in the imaging speed and the system design flexibility of a high-speed high-resolution FF-OCT system.
Poehlsgaard, Jacob; Harpsøe, Kasper; Jørgensen, Flemming Steen; Olsen, Lars
2012-02-27
The binding affinity of a drug-like molecule depends among other things on the availability of the bioactive conformation. If the bioactive conformation has a significantly higher energy than the global minimum energy conformation, then the molecule is unlikely to bind to its target. Determination of the global minimum energy conformation and calculation of conformational penalties of binding is a prerequisite for prediction of reliable binding affinities. Here, we present a simple and computationally efficient procedure to estimate the global energy minimum for a wide variety of structurally diverse molecules, including polar and charged compounds. Identifying global energy minimum conformations of such compounds with force field methods is problematic due to the exaggeration of intramolecular electrostatic interactions. We demonstrate that the global energy minimum conformations of zwitterionic compounds generated by conformational analysis with modified electrostatics are good approximations of the conformational distributions predicted by experimental data and with molecular dynamics performed in explicit solvent. Finally the method is used to calculate conformational penalties for zwitterionic GluA2 agonists and to filter false positives from a docking study. PMID:21985436
New design method based on sagittal flat-field equipment of Offner type imaging spectrometer
NASA Astrophysics Data System (ADS)
Ji, Yiqun; Xue, Rudong; Xu, Li; Shi, Rongbao; He, Hucheng; Shen, Weimin
2011-11-01
Based on the wave aberration theory, a new method of optical design of the planate symmetric Offner type imaging spectrometer is performed. Astigmatism changing with the diffraction angle of the grating, the meridional and saggital focusing characters are all studied. Determination of the initial configurations and optimally design methods of two improved types of Offner imaging spectrometer are discussed in detailed. A design example with the numerical aperture larger than 0.2, and the entrance slit 30mm is given. Its spectral resolution is better than 2nm and MTF is above 0.7@20lp/mm. The smile and keystone are less than 3% and 0.2% of the pixel respectively.
Al Abed, Amr; Yin, Shijie; Suaning, Gregg J; Lovell, Nigel H; Dokos, Socrates
2012-01-01
Computational models are valuable tools that can be used to aid the design and test the efficacy of electrical stimulation strategies in prosthetic vision devices. In continuum models of retinal electrophysiology, the effective extracellular potential can be considered as an approximate measure of the electrotonic loading a neuron's dendritic tree exerts on the soma. A convolution based method is presented to calculate the local spatial average of the effective extracellular loading in retinal ganglion cells (RGCs) in a continuum model of the retina which includes an active RGC tissue layer. The method can be used to study the effect of the dendritic tree size on the activation of RGCs by electrical stimulation using a hexagonal arrangement of electrodes (hexpolar) placed in the suprachoroidal space.
NASA Astrophysics Data System (ADS)
Matsumoto, S.
2016-09-01
The stress field is a key factor controlling earthquake occurrence and crustal evolution. In this study, we propose an approach for determining the stress field in a region using seismic moment tensors, based on the classical equation in plasticity theory. Seismic activity is a phenomenon that relaxes crustal stress and creates plastic strain in a medium because of faulting, which suggests that the medium could behave as a plastic body. Using the constitutive relation in plastic theory, the increment of the plastic strain tensor is proportional to the deviatoric stress tensor. Simple mathematical manipulation enables the development of an inversion method for estimating the stress field in a region. The method is tested on shallow earthquakes occurring on Kyushu Island, Japan.
NASA Astrophysics Data System (ADS)
Kim, Sungho; Ahn, Jae-Hyuk; Park, Tae Jung; Lee, Sang Yup; Choi, Yang-Kyu
2009-06-01
A unique direct electrical detection method of biomolecules, charge pumping, was demonstrated using a nanogap embedded field-effect-transistor (FET). With aid of a charge pumping method, sensitivity can fall below the 1 ng/ml concentration regime in antigen-antibody binding of an avian influenza case. Biomolecules immobilized in the nanogap are mainly responsible for the acute changes of the interface trap density due to modulation of the energy level of the trap. This finding is supported by a numerical simulation. The proposed detection method for biomolecules using a nanogap embedded FET represents a foundation for a chip-based biosensor capable of high sensitivity.
Latouche, Gwendal; Debord, Christian; Raynal, Marc; Milhade, Charlotte; Cerovic, Zoran G
2015-10-01
Early detection of fungal pathogen presence in the field would help to better time or avoid some of the fungicide treatments used to prevent crop production losses. We recently introduced a new phytoalexin-based method for a non-invasive detection of crop diseases using their fluorescence. The causal agent of grapevine downy mildew, Plasmopara viticola, induces the synthesis of stilbenoid phytoalexins by the host, Vitis vinifera, early upon infection. These stilbenoids emit violet-blue fluorescence under UV light. A hand-held solid-state UV-LED-based field fluorimeter, named Multiplex 330, was used to measure stilbenoid phytoalexins in a vineyard. It allowed us to non-destructively detect and monitor the naturally occurring downy mildew infections on leaves in the field. PMID:26293623
NASA Astrophysics Data System (ADS)
Sato, Takeshi; Ishikawa, Kenichi L.
2015-02-01
The time-dependent multiconfiguration self-consistent-field method based on the occupation-restricted multiple-active-space model is proposed (TD-ORMAS) for multielectron dynamics in intense laser fields. Extending the previously proposed time-dependent complete-active-space self-consistent-field method [TD-CASSCF; Phys. Rev. A 88, 023402 (2013), 10.1103/PhysRevA.88.023402], which divides the occupied orbitals into core and active orbitals, the TD-ORMAS method further subdivides the active orbitals into an arbitrary number of subgroups and poses the occupation restriction by giving the minimum and maximum number of electrons distributed in each subgroup. This enables highly flexible construction of the configuration-interaction (CI) space, allowing a large-active-space simulation of dynamics, e.g., the core excitation or ionization. The equations of motion for both CI coefficients and spatial orbitals are derived based on the time-dependent variational principle, and an efficient algorithm is proposed to solve for the orbital time derivatives. In-depth descriptions of the computational implementation are given in a readily programmable manner. The numerical application to the one-dimensional lithium hydride cluster models demonstrates that the high flexibility of the TD-ORMAS framework allows for the cost-effective simulations of multielectron dynamics by exploiting systematic series of approximations to the TD-CASSCF method.
NASA Astrophysics Data System (ADS)
Wang, Hua; Liu, Feng; Xia, Ling; Crozier, Stuart
2008-11-01
This paper presents a stabilized Bi-conjugate gradient algorithm (BiCGstab) that can significantly improve the performance of the impedance method, which has been widely applied to model low-frequency field induction phenomena in voxel phantoms. The improved impedance method offers remarkable computational advantages in terms of convergence performance and memory consumption over the conventional, successive over-relaxation (SOR)-based algorithm. The scheme has been validated against other numerical/analytical solutions on a lossy, multilayered sphere phantom excited by an ideal coil loop. To demonstrate the computational performance and application capability of the developed algorithm, the induced fields inside a human phantom due to a low-frequency hyperthermia device is evaluated. The simulation results show the numerical accuracy and superior performance of the method.
NASA Astrophysics Data System (ADS)
Bi, Chuan-Xing; Geng, Lin; Zhang, Xiao-Zheng
2016-05-01
In the sound field with multiple non-stationary sources, the measured pressure is the sum of the pressures generated by all sources, and thus cannot be used directly for studying the vibration and sound radiation characteristics of every source alone. This paper proposes a separation model based on the interpolated time-domain equivalent source method (ITDESM) to separate the pressure field belonging to every source from the non-stationary multi-source sound field. In the proposed method, ITDESM is first extended to establish the relationship between the mixed time-dependent pressure and all the equivalent sources distributed on every source with known location and geometry information, and all the equivalent source strengths at each time step are solved by an iterative solving process; then, the corresponding equivalent source strengths of one interested source are used to calculate the pressure field generated by that source alone. Numerical simulation of two baffled circular pistons demonstrates that the proposed method can be effective in separating the non-stationary pressure generated by every source alone in both time and space domains. An experiment with two speakers in a semi-anechoic chamber further evidences the effectiveness of the proposed method.
NASA Astrophysics Data System (ADS)
Davis, L. E.; Eves, R. L.
2006-12-01
Transitioning students from learner to investigator is best accomplished by incorporating research into the undergraduate classroom as a collaborative enterprise between students and faculty. Our course is a two-part design with a focus on a modern carbonate ecosystem and depositional environment on San Salvador Island, Bahamas in order to integrate geology, biology, and environmental science. Content background is provided in the classroom, which focuses on the geology of the Bahamian platform; the biological aspects of Caribbean island marine ecosystems; and the impact of human development on tropical islands. Application of course content is focused during an integrated field study of a specific carbonate environment, e.g. carbonate production in a tidal lagoon. The ultimate goals of the course are (1) identifying and acquiring both disciplinary and interdisciplinary research methodologies, (2) defining a specific investigative problem, (3) conducting `real' [meaningful] research, and (4) communicating research findings in the form of presentations at national meetings and publication in research journals. Assessment is based on specific criteria to be achieved during the research project. Criteria are determined through collaboration between faculty mentors and student researchers. Students are evaluated throughout the research phase with particular attention paid to an understanding of appropriate planning and background research, originality of thought; use of project-specific and appropriate data collection and sampling techniques; and analysis and interpretation of data. Students are expected to submit a final written report containing appropriate conclusions from data analysis and recommendations for further studies. Each student is also required to complete a self-assessment. The interdisciplinary experiences gained by faculty and students have already been incorporated into other courses and have led to publication of results. The course stimulates both
Method of depositing multi-layer carbon-based coatings for field emission
Sullivan, J.P.; Friedmann, T.A.
1999-08-10
A novel field emitter device is disclosed for cold cathode field emission applications, comprising a multi-layer resistive carbon film. The multi-layered film of the present invention is comprised of at least two layers of a resistive carbon material, preferably amorphous-tetrahedrally coordinated carbon, such that the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure comprises a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film comprises a plurality of carbon layers, wherein adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. Field emitters made according the present invention display improved electron emission characteristics in comparison to conventional field emitter materials. 8 figs.
Method of depositing multi-layer carbon-based coatings for field emission
Sullivan, John P.; Friedmann, Thomas A.
1999-01-01
A novel field emitter device for cold cathode field emission applications, comprising a multi-layer resistive carbon film. The multi-layered film of the present invention is comprised of at least two layers of a resistive carbon material, preferably amorphous-tetrahedrally coordinated carbon, such that the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure comprises a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film comprises a plurality of carbon layers, wherein adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. Field emitters made according the present invention display improved electron emission characteristics in comparison to conventional field emitter materials.
Variational methods for field theories
Ben-Menahem, S.
1986-09-01
Four field theory models are studied: Periodic Quantum Electrodynamics (PQED) in (2 + 1) dimensions, free scalar field theory in (1 + 1) dimensions, the Quantum XY model in (1 + 1) dimensions, and the (1 + 1) dimensional Ising model in a transverse magnetic field. The last three parts deal exclusively with variational methods; the PQED part involves mainly the path-integral approach. The PQED calculation results in a better understanding of the connection between electric confinement through monopole screening, and confinement through tunneling between degenerate vacua. This includes a better quantitative agreement for the string tensions in the two approaches. Free field theory is used as a laboratory for a new variational blocking-truncation approximation, in which the high-frequency modes in a block are truncated to wave functions that depend on the slower background modes (Boron-Oppenheimer approximation). This ''adiabatic truncation'' method gives very accurate results for ground-state energy density and correlation functions. Various adiabatic schemes, with one variable kept per site and then two variables per site, are used. For the XY model, several trial wave functions for the ground state are explored, with an emphasis on the periodic Gaussian. A connection is established with the vortex Coulomb gas of the Euclidean path integral approach. The approximations used are taken from the realms of statistical mechanics (mean field approximation, transfer-matrix methods) and of quantum mechanics (iterative blocking schemes). In developing blocking schemes based on continuous variables, problems due to the periodicity of the model were solved. Our results exhibit an order-disorder phase transition. The transfer-matrix method is used to find a good (non-blocking) trial ground state for the Ising model in a transverse magnetic field in (1 + 1) dimensions.
Sediment Toxicity Identification and Evaluation (TIE) methods have been developed for both interstitial waters and whole sediments. These relatively simple laboratory methods are designed to identify specific toxicants or classes of toxicants in sediments; however, the question ...
Shen, Hujun; Czaplewski, Cezary; Liwo, Adam; Scheraga, Harold A
2008-08-01
The kinetic-trapping problem in simulating protein folding can be overcome by using a Replica Exchange Method (REM). However, in implementing REM in molecular dynamics simulations, synchronization between processors on parallel computers is required, and communication between processors limits its ability to sample conformational space in a complex system efficiently. To minimize communication between processors during the simulation, a Serial Replica Exchange Method (SREM) has been proposed recently by Hagan et al. (J. Phys. Chem. B2007, 111, 1416-1423). Here, we report the implementation of this new SREM algorithm with our physics-based united-residue (UNRES) force field. The method has been tested on the protein 1E0L with a temperature-independent UNRES force field and on terminally blocked deca-alanine (Ala(10)) and 1GAB with the recently introduced temperature-dependent UNRES force field. With the temperature-independent force field, SREM reproduces the results of REM but is more efficient in terms of wall-clock time and scales better on distributed-memory machines. However, exact application of SREM to the temperature-dependent UNRES algorithm requires the determination of a four-dimensional distribution of UNRES energy components instead of a one-dimensional energy distribution for each temperature, which is prohibitively expensive. Hence, we assumed that the temperature dependence of the force field can be ignored for neighboring temperatures. This version of SREM worked for Ala(10) which is a simple system but failed to reproduce the thermodynamic results as well as regular REM on the more complex 1GAB protein. Hence, SREM can be applied to the temperature-independent but not to the temperature-dependent UNRES force field.
Shen, Hujun; Czaplewski, Cezary; Liwo, Adam; Scheraga, Harold A.
2009-01-01
The kinetic-trapping problem in simulating protein folding can be overcome by using a Replica Exchange Method (REM). However, in implementing REM in molecular dynamics simulations, synchronization between processors on parallel computers is required, and communication between processors limits its ability to sample conformational space in a complex system efficiently. To minimize communication between processors during the simulation, a Serial Replica Exchange Method (SREM) has been proposed recently by Hagan et al. (J. Phys. Chem. B 2007, 111, 1416–1423). Here, we report the implementation of this new SREM algorithm with our physics-based united-residue (UNRES) force field. The method has been tested on the protein 1E0L with a temperature-independent UNRES force field and on terminally blocked deca-alanine (Ala10) and 1GAB with the recently introduced temperature-dependent UNRES force field. With the temperature-independent force field, SREM reproduces the results of REM but is more efficient in terms of wall-clock time and scales better on distributed-memory machines. However, exact application of SREM to the temperature-dependent UNRES algorithm requires the determination of a four-dimensional distribution of UNRES energy components instead of a one-dimensional energy distribution for each temperature, which is prohibitively expensive. Hence, we assumed that the temperature dependence of the force field can be ignored for neighboring temperatures. This version of SREM worked for Ala10 which is a simple system but failed to reproduce the thermodynamic results as well as regular REM on the more complex 1GAB protein. Hence, SREM can be applied to the temperature-independent but not to the temperature-dependent UNRES force field. PMID:20011673
NASA Astrophysics Data System (ADS)
Meillier, Céline; Chatelain, Florent; Michel, Olivier; Bacon, Roland; Piqueras, Laure; Bacher, Raphael; Ayasso, Hacheme
2016-04-01
We present SELFI, the Source Emission Line FInder, a new Bayesian method optimized for detection of faint galaxies in Multi Unit Spectroscopic Explorer (MUSE) deep fields. MUSE is the new panoramic integral field spectrograph at the Very Large Telescope (VLT) that has unique capabilities for spectroscopic investigation of the deep sky. It has provided data cubes with 324 million voxels over a single 1 arcmin2 field of view. To address the challenge of faint-galaxy detection in these large data cubes, we developed a new method that processes 3D data either for modeling or for estimation and extraction of source configurations. This object-based approach yields a natural sparse representation of the sources in massive data fields, such as MUSE data cubes. In the Bayesian framework, the parameters that describe the observed sources are considered random variables. The Bayesian model leads to a general and robust algorithm where the parameters are estimated in a fully data-driven way. This detection algorithm was applied to the MUSE observation of Hubble Deep Field-South. With 27 h total integration time, these observations provide a catalog of 189 sources of various categories and with secured redshift. The algorithm retrieved 91% of the galaxies with only 9% false detection. This method also allowed the discovery of three new Lyα emitters and one [OII] emitter, all without any Hubble Space Telescope counterpart. We analyzed the reasons for failure for some targets, and found that the most important limitation of the method is when faint sources are located in the vicinity of bright spatially resolved galaxies that cannot be approximated by the Sérsic elliptical profile. The software and its documentation are available on the MUSE science web service (muse-vlt.eu/science).
Safari, Hesameddin; Rahimian, Mohammad Hassan; Krafczyk, Manfred
2014-09-01
In the present article, we extend and generalize our previous article [H. Safari, M. H. Rahimian, and M. Krafczyk, Phys. Rev. E 88, 013304 (2013)] to include the gradient of the vapor concentration at the liquid-vapor interface as the driving force for vaporization allowing the evaporation from the phase interface to work for arbitrary temperatures. The lattice Boltzmann phase-field multiphase modeling approach with a suitable source term, accounting for the effect of the phase change on the velocity field, is used to solve the two-phase flow field. The modified convective Cahn-Hilliard equation is employed to reconstruct the dynamics of the interface topology. The coupling between the vapor concentration and temperature field at the interface is modeled by the well-known Clausius-Clapeyron correlation. Numerous validation tests including one-dimensional and two-dimensional cases are carried out to demonstrate the consistency of the presented model. Results show that the model is able to predict the flow features around and inside an evaporating droplet quantitatively in quiescent as well as convective environments. PMID:25314562
Field-based evaluation of a male-specific (F+) RNA coliphage concentration method
Fecal contamination of water poses a significant risk to public health due to the potential presence of pathogens, including enteric viruses. Thus, sensitive, reliable and easy to use methods for the detection of microorganisms are needed to evaluate water quality. In this stud...
NASA Astrophysics Data System (ADS)
Schnetger, Bernhard; Dellwig, Olaf
2012-02-01
Experiments with water samples from the redoxclines of the Black Sea and the Baltic Sea identified a fraction of dissolved Mn which is completely oxidised to solid MnOx within less than 48 h at laboratory conditions. Disproportionation of this dissolved reactive Mn (dMnreact) into Mn (II) and Mn (IV) did not occur. Our data suggest that bacteria using oxygen are responsible for the fast oxidation of dMnreact. The operational definition of dMnreact is a Mn phase that passes a 0.45 μm filter, but can be separated from remaining dissolved Mn (II) by filtration 48 h after exposure to atmospheric oxygen. The application of this method to water samples from the redoxcline of the Black Sea reveals dMnreact profiles comparable to published Mn (III) profiles analysed by polarography thus identifying Mn (III) as the dominating constituent of dMnreact. As the degree of autocatalytic oxidation of dissolved Mn (II) by readily produced MnOx and microbial Mn (II) oxidation within the applied oxidation period is unknown, dMnreact is at least a semi-quantitative measure of dissolved Mn (III). Furthermore, the present method helps to assess the full potential for oxidation of dissolved Mn within aquatic ecosystems. This method has the advantage that sample preparation can be easily done on site, followed by analysis of dissolved Mn by conventional methods.
Zhang, Yu-Cun; Wei, Bin; Fu, Xian-Bin
2014-02-01
A temperature field detection method based on long-wavelength infrared spectrum for hot forging is proposed in the present paper. This method combines primary spectrum pyrometry and three-stage FP-cavity LCTF. By optimizing the solutions of three group nonlinear equations in the mathematical model of temperature detection, the errors are reduced, thus measuring results will be more objective and accurate. Then the system of three-stage FP-cavity LCTF was designed on the principle of crystal birefringence. The system realized rapid selection of any wavelength in a certain wavelength range. It makes the response of the temperature measuring system rapid and accurate. As a result, without the emissivity of hot forging, the method can acquire exact information of temperature field and effectively suppress the background light radiation around the hot forging and ambient light that impact the temperature detection accuracy. Finally, the results of MATLAB showed that the infrared spectroscopy through the three-stage FP-cavity LCTF could meet the requirements of design. And experiments verified the feasibility of temperature measuring method. Compared with traditional single-band thermal infrared imager, the accuracy of measuring result was improved. PMID:24822408
Variational Methods for Field Theories.
NASA Astrophysics Data System (ADS)
Ben-Menahem, Shahar
The thesis has four parts, dealing with four field theory models: Periodic Quantum Electrodynamics (PQED) in (2 + 1) dimensions, free scalar field theory in (1 + 1) dimensions, the Quantum XY model in (1 + 1) dimensions, and the (1 + 1) dimensional Ising model in a transverse magnetic field. The last three parts deal exclusively with variational methods; the PQED part involves mainly the path-integral approach. The PQED calculation results in a better understanding of the connection between electric confinement through monopole screening, and confinement through tunneling between degenerate vacua. This includes a better quantitative agreement for the string tensions in the two approaches. In the second part, we use free field theory as a loboratory for a new variational blocking-tuncation approximation, in which the high-frequency modes in a block are truncated to wave functions that depend on the slower background modes(Born-Oppenheimer approximation). This "adiabatic truncation" method gives very accurate results for ground -state energy density and correlation functions. Without the adiabatic method, a much larger number of state per block must be kept to get comparable results. Various adiabatic schemes, with one variable kept per site and then two variables per site, are used. For the XY model, several trial wave functions for the ground state are explored, with an emphasis on the periodic Gaussian. A connection is established with the vortex Coulomb gas of the Eclidean path integral approach. The approximations used are taken from the realms of statistical mechanics (mean field approximation, transfer-matrix methods) and of quantum mechanics (iterative blocking schemes). In developing blocking schemes based on continuous variables, problems due to the periodicity of the model were solved. Our results exhibit an order-disorder phase transition. This transition is a rudimentary version of the actual transition known to occur in the XY model, and is
NASA Astrophysics Data System (ADS)
Huang, Sheng; Ao, Xiang; Li, Yuan-yuan; Zhang, Rui
2016-09-01
In order to meet the needs of high-speed development of optical communication system, a construction method of quasi-cyclic low-density parity-check (QC-LDPC) codes based on multiplicative group of finite field is proposed. The Tanner graph of parity check matrix of the code constructed by this method has no cycle of length 4, and it can make sure that the obtained code can get a good distance property. Simulation results show that when the bit error rate ( BER) is 10-6, in the same simulation environment, the net coding gain ( NCG) of the proposed QC-LDPC(3 780, 3 540) code with the code rate of 93.7% in this paper is improved by 2.18 dB and 1.6 dB respectively compared with those of the RS(255, 239) code in ITU-T G.975 and the LDPC(3 2640, 3 0592) code in ITU-T G.975.1. In addition, the NCG of the proposed QC-LDPC(3 780, 3 540) code is respectively 0.2 dB and 0.4 dB higher compared with those of the SG-QC-LDPC(3 780, 3 540) code based on the two different subgroups in finite field and the AS-QC-LDPC(3 780, 3 540) code based on the two arbitrary sets of a finite field. Thus, the proposed QC-LDPC(3 780, 3 540) code in this paper can be well applied in optical communication systems.
Pernet, C.R.; Latinus, M.; Nichols, T.E.; Rousselet, G.A.
2015-01-01
Background In recent years, analyses of event related potentials/fields have moved from the selection of a few components and peaks to a mass-univariate approach in which the whole data space is analyzed. Such extensive testing increases the number of false positives and correction for multiple comparisons is needed. Method Here we review all cluster-based correction for multiple comparison methods (cluster-height, cluster-size, cluster-mass, and threshold free cluster enhancement – TFCE), in conjunction with two computational approaches (permutation and bootstrap). Results Data driven Monte-Carlo simulations comparing two conditions within subjects (two sample Student's t-test) showed that, on average, all cluster-based methods using permutation or bootstrap alike control well the family-wise error rate (FWER), with a few caveats. Conclusions (i) A minimum of 800 iterations are necessary to obtain stable results; (ii) below 50 trials, bootstrap methods are too conservative; (iii) for low critical family-wise error rates (e.g. p = 1%), permutations can be too liberal; (iv) TFCE controls best the type 1 error rate with an attenuated extent parameter (i.e. power < 1). PMID:25128255
Tavakkoli, Ehsan; Fatehi, Foad; Rengasamy, Pichu; McDonald, Glenn K
2012-06-01
Success in breeding crops for yield and other quantitative traits depends on the use of methods to evaluate genotypes accurately under field conditions. Although many screening criteria have been suggested to distinguish between genotypes for their salt tolerance under controlled environmental conditions, there is a need to test these criteria in the field. In this study, the salt tolerance, ion concentrations, and accumulation of compatible solutes of genotypes of barley with a range of putative salt tolerance were investigated using three growing conditions (hydroponics, soil in pots, and natural saline field). Initially, 60 genotypes of barley were screened for their salt tolerance and uptake of Na(+), Cl(-), and K(+) at 150 mM NaCl and, based on this, a subset of 15 genotypes was selected for testing in pots and in the field. Expression of salt tolerance in saline solution culture was not a reliable indicator of the differences in salt tolerance between barley plants that were evident in saline soil-based comparisons. Significant correlations were observed in the rankings of genotypes on the basis of their grain yield production at a moderately saline field site and their relative shoot growth in pots at EC(e) 7.2 [Spearman's rank correlation (rs)=0.79] and EC(e) 15.3 (rs=0.82) and the crucial parameter of leaf Na(+) (rs=0.72) and Cl(-) (rs=0.82) concentrations at EC(e) 7.2 dS m(-1). This work has established screening procedures that correlated well with grain yield at sites with moderate levels of soil salinity. This study also showed that both salt exclusion and osmotic tolerance are involved in salt tolerance and that the relative importance of these traits may differ with the severity of the salt stress. In soil, ion exclusion tended to be more important at low to moderate levels of stress but osmotic stress became more important at higher stress levels. Salt exclusion coupled with a synthesis of organic solutes were shown to be important components of
Tavakkoli, Ehsan; Fatehi, Foad; Rengasamy, Pichu; McDonald, Glenn K.
2012-01-01
Success in breeding crops for yield and other quantitative traits depends on the use of methods to evaluate genotypes accurately under field conditions. Although many screening criteria have been suggested to distinguish between genotypes for their salt tolerance under controlled environmental conditions, there is a need to test these criteria in the field. In this study, the salt tolerance, ion concentrations, and accumulation of compatible solutes of genotypes of barley with a range of putative salt tolerance were investigated using three growing conditions (hydroponics, soil in pots, and natural saline field). Initially, 60 genotypes of barley were screened for their salt tolerance and uptake of Na+, Cl–, and K+ at 150 mM NaCl and, based on this, a subset of 15 genotypes was selected for testing in pots and in the field. Expression of salt tolerance in saline solution culture was not a reliable indicator of the differences in salt tolerance between barley plants that were evident in saline soil-based comparisons. Significant correlations were observed in the rankings of genotypes on the basis of their grain yield production at a moderately saline field site and their relative shoot growth in pots at ECe 7.2 [Spearman’s rank correlation (rs)=0.79] and ECe 15.3 (rs=0.82) and the crucial parameter of leaf Na+ (rs=0.72) and Cl– (rs=0.82) concentrations at ECe 7.2 dS m−1. This work has established screening procedures that correlated well with grain yield at sites with moderate levels of soil salinity. This study also showed that both salt exclusion and osmotic tolerance are involved in salt tolerance and that the relative importance of these traits may differ with the severity of the salt stress. In soil, ion exclusion tended to be more important at low to moderate levels of stress but osmotic stress became more important at higher stress levels. Salt exclusion coupled with a synthesis of organic solutes were shown to be important components of salt
Yu, Xiao; Verho, Jarmo; Li, Tie; Kallio, Pasi; Vilkko, Matti; Gao, Anran; Wang, Yuelin
2014-01-01
Summary Silicon nanowire-based field-effect transistors (SiNW FETs) have demonstrated the ability of ultrasensitive detection of a wide range of biological and chemical targets. The detection is based on the variation of the conductance of a nanowire channel, which is caused by the target substance. This is seen in the voltage–current behavior between the drain and source. Some current, known as leakage current, flows between the gate and drain, and affects the current between the drain and source. Studies have shown that leakage current is frequency dependent. Measurements of such frequency characteristics can provide valuable tools in validating the functionality of the used transistor. The measurements can also be an advantage in developing new detection technologies utilizing SiNW FETs. The frequency-domain responses can be measured by using a commercial sine-sweep-based network analyzer. However, because the analyzer takes a long time, it effectively prevents the development of most practical applications. Another problem with the method is that in order to produce sinusoids the signal generator has to cope with a large number of signal levels. This may become challenging in developing low-cost applications. This paper presents fast, cost-effective frequency-domain methods with which to obtain the responses within seconds. The inverse-repeat binary sequence (IRS) is applied and the admittance spectroscopy between the drain and source is computed through Fourier methods. The methods is verified by experimental measurements from an n-type SiNW FET. PMID:25161832
NASA Astrophysics Data System (ADS)
Yin, Gang; Zhang, Yingtang; Mi, Songlin; Fan, Hongbo; Li, Zhining
2016-11-01
To obtain accurate magnetic gradient tensor data, a fast and robust calculation method based on regularized method in frequency domain was proposed. Using the potential field theory, the transform formula in frequency domain was deduced in order to calculate the magnetic gradient tensor from the pre-existing total magnetic anomaly data. By analyzing the filter characteristics of the Vertical vector transform operator (VVTO) and Gradient tensor transform operator (GTTO), we proved that the conventional transform process was unstable which would zoom in the high-frequency part of the data in which measuring noise locate. Due to the existing unstable problem that led to a low signal-to-noise (SNR) for the calculated result, we introduced regularized method in this paper. By selecting the optimum regularization parameters of different transform phases using the C-norm approach, the high frequency noise was restrained and the SNR was improved effectively. Numerical analysis demonstrates that most value and characteristics of the calculated data by the proposed method compare favorably with reference magnetic gradient tensor data. In addition, calculated magnetic gradient tensor components form real aeromagnetic survey provided better resolution of the magnetic sources and original profile.
Pettigrove, Vincent; Hoffmann, Ary
2005-01-01
A method using field-based microcosms was developed to determine the effects of contaminated sediments on aquatic macroinvertebrates. Fine sediments from nonpolluted, moderately polluted, and severely polluted bodies of water were placed in microcosms positioned within the littoral zone of a nonpolluted wetland near Melbourne (Victoria, Australia). In three experiments, 47 taxa, including 18 Chironomidae, 6 taxa from other Diptera families, and 7 Hemiptera taxa, colonized the microcosms, mostly via eggs deposited by flying adults. The effects of sediment type on the presence and abundance of common taxa were considered statistically. Pollution levels in sediments (indexed either by a principal components analysis or by the concentration of zinc, the predominant metal) resulted in reduced occurrence and abundance of eight taxa but had no effect on another five taxa. These findings were validated with an extensive field database for the distribution of macroinvertebrates and associated concentrations of zinc in sediments from streams and wetlands in the Melbourne region. The occurrence of eight taxa and the abundance of two taxa varied at similar zinc concentrations in sediments from both the microcosms and the field. Patterns for another two species did not match the microcosm results, but these groups contained multiple species with potentially diverse responses. The present results suggest that contaminant levels in sediments probably have a direct effect on the occurrence and abundance of macroinvertebrates in bodies of water in urban areas. The microcosm method can be used to gather information regarding the effects of sediment quality on macroinvertebrates in lentic habitats, particularly for indigenous species that cannot be easily reared or tested in laboratory conditions. Because almost all macroinvertebrates in microcosms develop from eggs, the most sensitive life stages (i.e., first and second instars) are exposed to polluted sediments.
NASA Astrophysics Data System (ADS)
Lee, J. H.; Lee, Sang Young
2006-10-01
In obtaining the intrinsic surface resistance (RS) from the effective surface resistance (RS,eff) measured at microwave frequencies by using the dielectric resonator method, the impedance transformation method reported by Klein et al. [N. Klein, H. Chaloupka, G. Muller, S. Orbach, H. Piel, B. Roas, L. Schultz, U. Klein, M. Peiniger, J. Appl. Phys. 67 (1990) 6940] has been very useful. Here we compared the RS of YBa2Cu3O7-δ (YBCO) films on dielectric substrates obtained by a rigorous field analysis based on the TE-mode matching method with those by the impedance transformation method. The two methods produced almost the same RS,eff vs. RS relation in most practical cases of the substrate thickness being less than 1 mm and sapphire and rutile used as the materials for the dielectric rod. However, when the resonant frequency of the dielectric resonator became close to that of the resonant structure formed by the substrates and the metallic surroundings, the RS,eff vs. RS relations appeared strikingly different between the two methods. Effects of the TE011-mode cutoff frequency inside the substrate region, which could not be considered in the impedance transformation method, on the relation between the RS,eff and RS of superconductor films are also investigated. We confirmed our arguments by demonstrating a case where existence of evanescent modes should be considered for obtaining the RS of YBCO films from the RS,eff.
NASA Astrophysics Data System (ADS)
Li, H. B.; Wang, X.
2016-05-01
This paper reports the result of investigation into the morphological evolution and migration of void in bi-piezoelectric material interface by utilizing nonlocal phase field model and finite element method (FEM), where the small scale effect containing the long-range forces among atoms is considered. The nonlocal elastic strain energy and the nonlocal electric energy around the void are firstly calculated by the finite element method. Then based on the finite difference method (FDM), the thermodynamic equilibrium equation containing the surface energy and anisotropic diffusivity is solved to simulate the morphological evolution and migration of elliptical void in bi-piezoelectric films interface. Results show that the way of load condition plays a significant role in the evolution process, and the boundary of void's long axis gradually collapses toward the center of ellipse. In addition, the evolutionary speed of left boundary gradually decreases with scale effect coefficient growth. This work can provide references for the safety evaluation of piezoelectric materials in micro electro mechanical system.
A simple non-invasive field based method for examining and parameterizing root-water-uptake models
NASA Astrophysics Data System (ADS)
Yang, y.; Guan, h.; Huston, J.; Wang, h.; Ewenz, C.; Shang, s.; Simmons, C.
2012-04-01
A simple non-invasive field based method for directly parameterizing root-water-uptake models is proposed. Stem psychrometers and sap flow meters are used to measure stem water potential and plant transpiration rate continuously and simultaneously. Predawn stem water potential is selected as a surrogate for root-zone soil water potential to examine and parameterize the root water-uptake water stress response functions. The method is applied to two drooping sheoak (Allocasuarina verticillata) trees for a period of 80 days, covering both a dry season and a wet season. The result indicates that the S-shape function is more appropriate than the Feddes piecewise linear function for drooping sheoak to explain the effect of soil moisture stress on its root water uptake performance. Besides, the water stress function was found to be not only the function of soil moisture, but also dependent on the atmospheric demand. As the result, the S-shape water stress function is corrected considering the effect of atmospheric conditions. The soil moisture modeling results indicated that the proposed method is capable in correctly choosing and calibrating the root-water-uptake models. In addition, the S-shape water stress function with atmospheric correction performed better than the classical S-shape function in modeling both root zone soil water potential and plant transpiration rate.
NASA Astrophysics Data System (ADS)
Chibani, Wael; Ren, Xinguo; Scheffler, Matthias; Rinke, Patrick
2016-04-01
We present an embedding scheme for periodic systems that facilitates the treatment of the physically important part (here a unit cell or a supercell) with advanced electronic structure methods, that are computationally too expensive for periodic systems. The rest of the periodic system is treated with computationally less demanding approaches, e.g., Kohn-Sham density-functional theory, in a self-consistent manner. Our scheme is based on the concept of dynamical mean-field theory formulated in terms of Green's functions. Our real-space dynamical mean-field embedding scheme features two nested Dyson equations, one for the embedded cluster and another for the periodic surrounding. The total energy is computed from the resulting Green's functions. The performance of our scheme is demonstrated by treating the embedded region with hybrid functionals and many-body perturbation theory in the GW approach for simple bulk systems. The total energy and the density of states converge rapidly with respect to the computational parameters and approach their bulk limit with increasing cluster (i.e., computational supercell) size.
NASA Astrophysics Data System (ADS)
Liu, Xiaoming; Mei, Ming; Liu, Jun; Hu, Wei
2015-12-01
Clustered microcalcifications (MCs) in mammograms are an important early sign of breast cancer in women. Their accurate detection is important in computer-aided detection (CADe). In this paper, we integrated the possibilistic fuzzy c-means (PFCM) clustering algorithm and weighted support vector machine (WSVM) for the detection of MC clusters in full-field digital mammograms (FFDM). For each image, suspicious MC regions are extracted with region growing and active contour segmentation. Then geometry and texture features are extracted for each suspicious MC, a mutual information-based supervised criterion is used to select important features, and PFCM is applied to cluster the samples into two clusters. Weights of the samples are calculated based on possibilities and typicality values from the PFCM, and the ground truth labels. A weighted nonlinear SVM is trained. During the test process, when an unknown image is presented, suspicious regions are located with the segmentation step, selected features are extracted, and the suspicious MC regions are classified as containing MC or not by the trained weighted nonlinear SVM. Finally, the MC regions are analyzed with spatial information to locate MC clusters. The proposed method is evaluated using a database of 410 clinical mammograms and compared with a standard unweighted support vector machine (SVM) classifier. The detection performance is evaluated using response receiver operating (ROC) curves and free-response receiver operating characteristic (FROC) curves. The proposed method obtained an area under the ROC curve of 0.8676, while the standard SVM obtained an area of 0.8268 for MC detection. For MC cluster detection, the proposed method obtained a high sensitivity of 92 % with a false-positive rate of 2.3 clusters/image, and it is also better than standard SVM with 4.7 false-positive clusters/image at the same sensitivity.
Teaching Geographic Field Methods Using Paleoecology
ERIC Educational Resources Information Center
Walsh, Megan K.
2014-01-01
Field-based undergraduate geography courses provide numerous pedagogical benefits including an opportunity for students to acquire employable skills in an applied context. This article presents one unique approach to teaching geographic field methods using paleoecological research. The goals of this course are to teach students key geographic…
Liu, Feng; Crozier, Stuart
2004-08-01
This paper evaluates a new, low-frequency finite-difference time-domain method applied to the problem of induced E-fields/eddy currents in the human body resulting from the pulsed magnetic field gradients in MRI. In this algorithm, a distributed equivalent magnetic current is proposed as the electromagnetic source and is obtained by quasistatic calculation of the empty coil's vector potential or measurements therein. This technique circumvents the discretization of complicated gradient coil geometries into a mesh of Yee cells, and thereby enables any type of gradient coil modelling or other complex low frequency sources. The proposed method has been verified against an example with an analytical solution. Results are presented showing the spatial distribution of gradient-induced electric fields in a multi-layered spherical phantom model and a complete body model.
Field method for sulfide determination
Wilson, B L; Schwarser, R R; Chukwuenye, C O
1982-01-01
A simple and rapid method was developed for determining the total sulfide concentration in water in the field. Direct measurements were made using a silver/sulfide ion selective electrode in conjunction with a double junction reference electrode connected to an Orion Model 407A/F Specific Ion Meter. The method also made use of a sulfide anti-oxidant buffer (SAOB II) which consists of ascorbic acid, sodium hydroxide, and disodium EDTA. Preweighed sodium sulfide crystals were sealed in air tight plastic volumetric flasks which were used in standardization process in the field. Field standards were prepared by adding SAOB II to the flask containing the sulfide crystals and diluting it to the mark with deionized deaerated water. Serial dilutions of the standards were used to prepare standards of lower concentrations. Concentrations as low as 6 ppB were obtained on lake samples with a reproducibility better than +- 10%.
ERIC Educational Resources Information Center
Varma, Tina; Volkmann, Mark; Hanuscin, Deborah
2009-01-01
Literature indicates that the "National Science Education Standards" ("NSES") teaching standards and inquiry-based teaching strategies for science are not uniformly incorporated into the elementary science methods (eSEM) courses across the U.S. and that field experiences might not provide appropriate models of the inquiry-based science pedagogy…
Variational methods for field theories
NASA Astrophysics Data System (ADS)
Ben-Menahem, Shahar
1986-09-01
The thesis is presented in four parts dealing with field theory models: Periodic Quantum Electrodynamics (PQED) in (2+1) dimensions, free scalar field theory in (1+1) dimensions, the Quantum XY model in (1+1) dimensions, and the (1+1) dimensional Ising model in a transverse magnetic field. The last three parts deal exclusively with variational methods; the PQED part involves mainly the path integral approach. The PQED calculation results in a better understanding of the connection between electric confinement through monopole screening, and confinement through tunneling between degenerate vacua. Free field theory is used as a laboratory for a new variational blocking truncation approximation, in which the high frequency modes in a block are truncated to wave functions that depend on the slower background model (Born Oppenheimer approximation). For the XY model, several trial wave functions for the ground state are explored, with an emphasis on the periodic Gaussian. In the 4th part, the transfer matrix method is used to find a good (non blocking) trial ground state for the Ising model in a transverse magnetic field in (1+1) dimensions.
NASA Astrophysics Data System (ADS)
Maki, Toshihiro; Ura, Tamaki; Singh, Hanumant; Sakamaki, Takashi
Large-area seafloor imaging will bring significant benefits to various fields such as academics, resource survey, marine development, security, and search-and-rescue. The authors have proposed a navigation method of an autonomous underwater vehicle for seafloor imaging, and verified its performance through mapping tubeworm colonies with the area of 3,000 square meters using the AUV Tri-Dog 1 at Tagiri vent field, Kagoshima bay in Japan (Maki et al., 2008, 2009). This paper proposes a post-processing method to build a natural photo mosaic from a number of pictures taken by an underwater platform. The method firstly removes lens distortion, invariances of color and lighting from each image, and then ortho-rectification is performed based on camera pose and seafloor estimated by navigation data. The image alignment is based on both navigation data and visual characteristics, implemented as an expansion of the image based method (Pizarro et al., 2003). Using the two types of information realizes an image alignment that is consistent both globally and locally, as well as making the method applicable to data sets with little visual keys. The method was evaluated using a data set obtained by the AUV Tri-Dog 1 at the vent field in Sep. 2009. A seamless, uniformly illuminated photo mosaic covering the area of around 500 square meters was created from 391 pictures, which covers unique features of the field such as bacteria mats and tubeworm colonies.
Hohenstein, Edward G.; Luehr, Nathan; Ufimtsev, Ivan S.; Martínez, Todd J.
2015-06-14
Despite its importance, state-of-the-art algorithms for performing complete active space self-consistent field (CASSCF) computations have lagged far behind those for single reference methods. We develop an algorithm for the CASSCF orbital optimization that uses sparsity in the atomic orbital (AO) basis set to increase the applicability of CASSCF. Our implementation of this algorithm uses graphical processing units (GPUs) and has allowed us to perform CASSCF computations on molecular systems containing more than one thousand atoms. Additionally, we have implemented analytic gradients of the CASSCF energy; the gradients also benefit from GPU acceleration as well as sparsity in the AO basis.
Chakraborty, Pritam; Zhang, Yongfeng; Tonks, Michael R.
2015-12-07
In this study, the fracture behavior of brittle materials is strongly influenced by their underlying microstructure that needs explicit consideration for accurate prediction of fracture properties and the associated scatter. In this work, a hierarchical multi-scale approach is pursued to model microstructure sensitive brittle fracture. A quantitative phase-field based fracture model is utilized to capture the complex crack growth behavior in the microstructure and the related parameters are calibrated from lower length scale atomistic simulations instead of engineering scale experimental data. The workability of this approach is demonstrated by performing porosity dependent intergranular fracture simulations in UO_{2} and comparing the predictions with experiments.
NASA Astrophysics Data System (ADS)
Yang, Kang; Guo, Zhaoli
2016-04-01
In this paper, a lattice Boltzmann equation (LBE) model is proposed for binary fluids based on a quasi-incompressible phase-field model [J. Shen et al., Commun. Comput. Phys. 13, 1045 (2013), 10.4208/cicp.300711.160212a]. Compared with the other incompressible LBE models based on the incompressible phase-field theory, the quasi-incompressible model conserves mass locally. A series of numerical simulations are performed to validate the proposed model, and comparisons with an incompressible LBE model [H. Liang et al., Phys. Rev. E 89, 053320 (2014), 10.1103/PhysRevE.89.053320] are also carried out. It is shown that the proposed model can track the interface accurately. As the stationary droplet and rising bubble problems, the quasi-incompressible LBE gives nearly the same predictions as the incompressible model, but the compressible effect in the present model plays a significant role in the phase separation problem. Therefore, in general cases the present mass-conserving model should be adopted.
Modified methods of stellar magnetic field measurements
NASA Astrophysics Data System (ADS)
Kholtygin, A. F.
2014-12-01
The standard methods of the magnetic field measurement, based on an analysis of the relation between the Stokes V-parameter and the first derivative of the total line profile intensity, were modified by applying a linear integral operator \\hat{L} to both sides of this relation. As the operator \\hat{L}, the operator of the wavelet transform with DOG-wavelets is used. The key advantage of the proposed method is an effective suppression of the noise contribution to the line profile and the Stokes parameter V. The efficiency of the method has been studied using model line profiles with various noise contributions. To test the proposed method, the spectropolarimetric observations of the A0 star α2 CVn, the Of?p star HD 148937, and the A0 supergiant HD 92207 were used. The longitudinal magnetic field strengths calculated by our method appeared to be in good agreement with those determined by other methods.
Chakraborty, Pritam; Zhang, Yongfeng; Tonks, Michael R.
2015-12-07
In this study, the fracture behavior of brittle materials is strongly influenced by their underlying microstructure that needs explicit consideration for accurate prediction of fracture properties and the associated scatter. In this work, a hierarchical multi-scale approach is pursued to model microstructure sensitive brittle fracture. A quantitative phase-field based fracture model is utilized to capture the complex crack growth behavior in the microstructure and the related parameters are calibrated from lower length scale atomistic simulations instead of engineering scale experimental data. The workability of this approach is demonstrated by performing porosity dependent intergranular fracture simulations in UO2 and comparing themore » predictions with experiments.« less
Xiao, Xiao; Hua, Xue-Ming; Wu, Yi-Xiong; Li, Fang
2012-09-01
Pulsed TIG welding is widely used in industry due to its superior properties, and the measurement of arc temperature is important to analysis of welding process. The relationship between particle densities of Ar and temperature was calculated based on the theory of spectrum, the relationship between emission coefficient of spectra line at 794.8 nm and temperature was calculated, arc image of spectra line at 794.8 nm was captured by high speed camera, and both the Abel inversion and Fowler-Milne method were used to calculate the temperature distribution of pulsed TIG welding. PMID:23240389
NASA Astrophysics Data System (ADS)
Sharifi hashjin, S.; Darvishi, A.; Khazai, S.; Hatami, F.; Jafari houtki, M.
2016-06-01
In recent years, developing target detection algorithms has received growing interest in hyperspectral images. In comparison to the classification field, few studies have been done on dimension reduction or band selection for target detection in hyperspectral images. This study presents a simple method to remove bad bands from the images in a supervised manner for sub-pixel target detection. The proposed method is based on comparing field and laboratory spectra of the target of interest for detecting bad bands. For evaluation, the target detection blind test dataset is used in this study. Experimental results show that the proposed method can improve efficiency of the two well-known target detection methods, ACE and CEM.
Field evaluation of a VOST sampling method
Jackson, M.D.; Johnson, L.D.; Fuerst, R.G.; McGaughey, J.F.; Bursey, J.T.; Merrill, R.G.
1994-12-31
The VOST (SW-846 Method 0030) specifies the use of Tenax{reg_sign} and a particular petroleum-based charcoal (SKC Lot 104, or its equivalent), that is no longer commercially available. In field evaluation studies of VOST methodology, a replacement petroleum-based charcoal has been used: candidate replacement sorbents for charcoal were studied, and Anasorb{reg_sign} 747, a carbon-based sorbent, was selected for field testing. The sampling train was modified to use only Anasorb{reg_sign} in the back tube and Tenax{reg_sign} in the two front tubes to avoid analytical difficulties associated with the analysis of the sequential bed back tube used in the standard VOST train. The standard (SW-846 Method 0030) and the modified VOST methods were evaluated at a chemical manufacturing facility using a quadruple probe system with quadruple trains. In this field test, known concentrations of the halogenated volatile organic compounds, that are listed in the Clean Air Act Amendments of 1990, Title 3, were introduced into the VOST train and the modified VOST train, using the same certified gas cylinder as a source of test compounds. Statistical tests of the comparability of methods were performed on a compound-by-compound basis. For most compounds, the VOST and modified VOST methods were found to be statistically equivalent.
NASA Astrophysics Data System (ADS)
Lopes, Thiago; Ho, Matthew; Kakati, Biraj K.; Kucernak, Anthony R. J.
2015-01-01
A new, simple and precise ex-situ optical imaging method is developed which allows indirect measurement of the partial pressure of oxygen (as ozone) within fuel cell components. Images of oxygen distribution are recorded with higher spatial (∼20 μm) and time (40 ms) resolutions. This approach is applied to assess oxygen concentration across the face of a pseudo polymer electrolyte fuel cell (PEFC), with a serpentine design flow field. We show that the amount of light produced is directly proportional to the partial pressure of ozone, in the same way as the local current density in a PEFC is proportional to the partial pressure of bimolecular oxygen. Hence the simulated system provides information relevant to a PEFC with the same geometry operating at the same stoichiometric ratio. This new approach allows direct imaging of flow under lands due to pressure gradients between the adjacent channels and non-laminar flow effects due to secondary flow around U-turns. These are major discoveries of fundamental importance in guiding materials development and in validating modelling studies. We find that contrary to many simulation papers, advection is an important mechanism in both the gas diffusion layer (more properly "reactant transport layer") and the microporous layer. Models which do not include these effects may underestimate reactant transport to the catalyst layer.
NASA Astrophysics Data System (ADS)
Barchyn, Thomas Edward
Aeolian sediment transport threshold is commonly defined as the minimum wind speed (or shear stress) necessary for wind-driven sediment transport. Threshold is a core parameter in most models of aeolian transport. Recent advances in methodology for field-based measurement of threshold show promise for improving parameterizations; however, investigators have varied in choice of method and sensor. The impacts of modifying measurement system configuration are unknown. To address this, two field tests were performed: (i) comparison of four piezoelectric sediment transport sensors, and (ii) comparison of four calculation methods. Data from both comparisons suggest that threshold measurements are non-negligibly modified by measurement system configuration and are incomparable. A poor understanding of natural sediment transport dynamics suggests that development of calibration methods could be difficult. Development of technical standards was explored to improve commensurability of measurements. Standards could assist future researchers with data syntheses and integration.
Liu, Ji; Yu, Li-xia; Zhang, Bin; Zhao Dong-e; Liij, Xiao-yan; Wang, Heng-fei
2016-03-01
The deflagration fire lasting for a long time and covering a large area in the process of large equivalent explosion makes it difficult to obtain velocity parameters of fragments in the near-field. In order to solve the problem, it is proposed in this paper a photoelectric transceiver integrated method which utilize laser screen as the sensing area. The analysis of three different types of warhead explosion flame spectral distribution of radiation shows that 0.3 to 1.0 μm within the band is at relatively low intensity. On the basis of this, the optical system applies the principle of determining the fixed distance by measuring the time and the reflector technology, which consists of single longitudinal mode laser, cylindrical Fresnel lens, narrow-band filters and high-speed optical sensors, etc. The system has its advantage, such as transceiver, compact structure and combination of narrowband filter and single longitudinal mode laser, which can stop the spectrum of fire from suppressing the interference of background light effectively. Large amounts of experiments in different models and equivalent have been conducted to measure the velocity of difference kinds of warheads, obtaining higher signal-to-noise ratio of the waveform signal after a series of signal de-noising and recognition through NI company data acquisition and recording system. The experimental results show that this method can complete the accurately test velocity of fragments around center of the explosion. Specifically, the minimum size of fragments can be measured is 4 mm while the speed can be obtained is up to 1 200 m x s(-1) and the capture rate is better than 95% comparing with test results of target plate. At the same time, the system adopts Fresnel lenses-transparent to form a rectangular screen, which makes the distribution of rectangular light uniform in vertical direction, and the light intensity uniformity in horizontal direction is more than 80%. Consequently, the system can
Liu, Ji; Yu, Li-xia; Zhang, Bin; Zhao Dong-e; Liij, Xiao-yan; Wang, Heng-fei
2016-03-01
The deflagration fire lasting for a long time and covering a large area in the process of large equivalent explosion makes it difficult to obtain velocity parameters of fragments in the near-field. In order to solve the problem, it is proposed in this paper a photoelectric transceiver integrated method which utilize laser screen as the sensing area. The analysis of three different types of warhead explosion flame spectral distribution of radiation shows that 0.3 to 1.0 μm within the band is at relatively low intensity. On the basis of this, the optical system applies the principle of determining the fixed distance by measuring the time and the reflector technology, which consists of single longitudinal mode laser, cylindrical Fresnel lens, narrow-band filters and high-speed optical sensors, etc. The system has its advantage, such as transceiver, compact structure and combination of narrowband filter and single longitudinal mode laser, which can stop the spectrum of fire from suppressing the interference of background light effectively. Large amounts of experiments in different models and equivalent have been conducted to measure the velocity of difference kinds of warheads, obtaining higher signal-to-noise ratio of the waveform signal after a series of signal de-noising and recognition through NI company data acquisition and recording system. The experimental results show that this method can complete the accurately test velocity of fragments around center of the explosion. Specifically, the minimum size of fragments can be measured is 4 mm while the speed can be obtained is up to 1 200 m x s(-1) and the capture rate is better than 95% comparing with test results of target plate. At the same time, the system adopts Fresnel lenses-transparent to form a rectangular screen, which makes the distribution of rectangular light uniform in vertical direction, and the light intensity uniformity in horizontal direction is more than 80%. Consequently, the system can
NASA Astrophysics Data System (ADS)
Kyllmar, K.; Mårtensson, K.; Johnsson, H.
2005-03-01
A method to calculate N leaching from arable fields using model-calculated N leaching coefficients (NLCs) was developed. Using the process-based modelling system SOILNDB, leaching of N was simulated for four leaching regions in southern Sweden with 20-year climate series and a large number of randomised crop sequences based on regional agricultural statistics. To obtain N leaching coefficients, mean values of annual N leaching were calculated for each combination of main crop, following crop and fertilisation regime for each leaching region and soil type. The field-NLC method developed could be useful for following up water quality goals in e.g. small monitoring catchments, since it allows normal leaching from actual crop rotations and fertilisation to be determined regardless of the weather. The method was tested using field data from nine small intensively monitored agricultural catchments. The agreement between calculated field N leaching and measured N transport in catchment stream outlets, 19-47 and 8-38 kg ha -1 yr -1, respectively, was satisfactory in most catchments when contributions from land uses other than arable land and uncertainties in groundwater flows were considered. The possibility of calculating effects of crop combinations (crop and following crop) is of considerable value since changes in crop rotation constitute a large potential for reducing N leaching. When the effect of a number of potential measures to reduce N leaching (i.e. applying manure in spring instead of autumn; postponing ploughing-in of ley and green fallow in autumn; undersowing a catch crop in cereals and oilseeds; and increasing the area of catch crops by substituting winter cereals and winter oilseeds with corresponding spring crops) was calculated for the arable fields in the catchments using field-NLCs, N leaching was reduced by between 34 and 54% for the separate catchments when the best possible effect on the entire potential area was assumed.
New Methods of Magnetic Field Measurements
NASA Astrophysics Data System (ADS)
Kholtygin, A. F.
2015-04-01
The standard methods of magnetic field measurements, based on the relation between the Stokes V parameter and the first derivative of the line profile intensity were modified by applying a linear integral transform to both sides of this relation. We used the wavelet integral transform with the DOG wavelets. The key advantage of the proposed method is the effective suppression of the noise contribution both to the line profile and the Stokes V parameter. To test the proposed method, spectropolarimetric observations of the young O star θ1 Ori C were used. We also demonstrate that the smoothed Time Variation Spectra (smTVS) can be used as a tool for detecting the local stellar magnetic fields.
NASA Astrophysics Data System (ADS)
Leiva Lopez, Josue Nahun
In general, the nursery industry lacks an automated inventory control system. Object-based image analysis (OBIA) software and aerial images could be used to count plants in nurseries. The objectives of this research were: 1) to evaluate the effect of an unmanned aerial vehicle (UAV) flight altitude and plant canopy separation of container-grown plants on count accuracy using aerial images and 2) to evaluate the effect of plant canopy shape, presence of flowers, and plant status (living and dead) on counting accuracy of container-grown plants using remote sensing images. Images were analyzed using Feature AnalystRTM (FA) and an algorithm trained using MATLABRTM. Total count error, false positives and unidentified plants were recorded from output images using FA; only total count error was reported for the MATLAB algorithm. For objective 1, images were taken at 6, 12 and 22 m above the ground using a UAV. Plants were placed on black fabric and gravel, and spaced as follows: 5 cm between canopy edges, canopy edges touching, and 5 cm of canopy edge overlap. In general, when both methods were considered, total count error was smaller [ranging from -5 (undercount) to 4 (over count)] when plants were fully separated with the exception of images taken at 22 m. FA showed a smaller total count error (-2) than MATLAB (-5) when plants were placed on black fabric than those placed on gravel. For objective 2, the plan was to continue using the UAV, however, due to the unexpected disruption of the GPS-based navigation by heightened solar flare activity in 2013, a boom lift that could provide images on a more reliable basis was used. When images obtained using a boom lift were analyzed using FA there was no difference between variables measured when an algorithm trained with an image displaying regular or irregular plant canopy shape was applied to images displaying both plant canopy shapes even though the canopy shape of 'Sea Green' juniper is less compact than 'Plumosa Compacta
Computer Based Virtual Field Trips.
ERIC Educational Resources Information Center
Clark, Kenneth F.; Hosticka, Alice; Schriver, Martha; Bedell, Jackie
This paper discusses computer based virtual field trips that use technologies commonly found in public schools in the United States. The discussion focuses on the advantages of both using and creating these field trips for an instructional situation. A virtual field trip to Cumberland Island National Seashore, St. Marys, Georgia is used as a point…
Apparatuses and methods for generating electric fields
Scott, Jill R; McJunkin, Timothy R; Tremblay, Paul L
2013-08-06
Apparatuses and methods relating to generating an electric field are disclosed. An electric field generator may include a semiconductive material configured in a physical shape substantially different from a shape of an electric field to be generated thereby. The electric field is generated when a voltage drop exists across the semiconductive material. A method for generating an electric field may include applying a voltage to a shaped semiconductive material to generate a complex, substantially nonlinear electric field. The shape of the complex, substantially nonlinear electric field may be configured for directing charged particles to a desired location. Other apparatuses and methods are disclosed.
NASA Astrophysics Data System (ADS)
Galanti, Eli; Kaspi, Yohai
2016-04-01
During 2016-17, the Juno and Cassini spacecraft will both perform close eccentric orbits of Jupiter and Saturn, respectively, obtaining high-precision gravity measurements for these planets. These data will be used to estimate the depth of the observed surface flows on these planets. All models to date, relating the winds to the gravity field, have been in the forward direction, thus only allowing the calculation of the gravity field from given wind models. However, there is a need to do the inverse problem since the new observations will be of the gravity field. Here, an inverse dynamical model is developed to relate the expected measurable gravity field, to perturbations of the density and wind fields, and therefore to the observed cloud-level winds. In order to invert the gravity field into the 3D circulation, an adjoint model is constructed for the dynamical model, thus allowing backward integration. This tool is used for the examination of various scenarios, simulating cases in which the depth of the wind depends on latitude. We show that it is possible to use the gravity measurements to derive the depth of the winds, both on Jupiter and Saturn, also taking into account measurement errors. Calculating the solution uncertainties, we show that the wind depth can be determined more precisely in the low-to-mid-latitudes. In addition, the gravitational moments are found to be particularly sensitive to flows at the equatorial intermediate depths. Therefore, we expect that if deep winds exist on these planets they will have a measurable signature by Juno and Cassini.
Zhao, Qian; Jia, Xiaobo; Xia, Rui; Lin, Jianing; Zhang, Yuan
2016-09-01
Ionic mixtures, measured as specific conductivity, have been increasingly concerned because of their toxicities to aquatic organisms. However, identifying protective values of specific conductivity for aquatic organisms is challenging given that laboratory test systems cannot examine more salt-intolerant species nor effects occurring in streams. Large data sets used for deriving field-based benchmarks are rarely available. In this study, a field-based method for small data sets was used to derive specific conductivity benchmark, which is expected to prevent the extirpation of 95% of local taxa from circum-neutral to alkaline waters dominated by a mixture of SO4(2-) and HCO3(-) anions and other dissolved ions. To compensate for the smaller sample size, species level analyses were combined with genus level analyses. The benchmark is based on extirpation concentration (XC95) values of specific conductivity for 60 macroinvertebrate genera estimated from 296 sampling sites in the Hun-Tai River Basin. We derived the specific conductivity benchmark by using a 2-point interpolation method, which yielded the benchmark of 249 μS/cm. Our study tailored the method that was developed by USEPA to derive aquatic life benchmark for specific conductivity for basin scale application, and may provide useful information for water pollution control and management.
Zhao, Qian; Jia, Xiaobo; Xia, Rui; Lin, Jianing; Zhang, Yuan
2016-09-01
Ionic mixtures, measured as specific conductivity, have been increasingly concerned because of their toxicities to aquatic organisms. However, identifying protective values of specific conductivity for aquatic organisms is challenging given that laboratory test systems cannot examine more salt-intolerant species nor effects occurring in streams. Large data sets used for deriving field-based benchmarks are rarely available. In this study, a field-based method for small data sets was used to derive specific conductivity benchmark, which is expected to prevent the extirpation of 95% of local taxa from circum-neutral to alkaline waters dominated by a mixture of SO4(2-) and HCO3(-) anions and other dissolved ions. To compensate for the smaller sample size, species level analyses were combined with genus level analyses. The benchmark is based on extirpation concentration (XC95) values of specific conductivity for 60 macroinvertebrate genera estimated from 296 sampling sites in the Hun-Tai River Basin. We derived the specific conductivity benchmark by using a 2-point interpolation method, which yielded the benchmark of 249 μS/cm. Our study tailored the method that was developed by USEPA to derive aquatic life benchmark for specific conductivity for basin scale application, and may provide useful information for water pollution control and management. PMID:27389551
Casti, Paola; Mencattini, Arianna; Salmeri, Marcello; Ancona, Antonietta; Mangieri, Fabio Felice; Pepe, Maria Luisa; Rangayyan, Rangaraj Mandayam
2013-10-01
Automatic detection of the nipple in mammograms is an important step in computerized systems that combine multiview information for accurate detection and diagnosis of breast cancer. Locating the nipple is a difficult task owing to variations in image quality, presence of noise, and distortion and displacement of the breast tissue due to compression. In this work, we propose a novel Hessian-based method to locate automatically the nipple in screen-film and full-field digital mammograms (FFDMs). The method includes detection of a plausible nipple/retroareolar area in a mammogram using geometrical constraints, analysis of the gradient vector field by mean and Gaussian curvature measurements, and local shape-based conditions. The proposed procedure was tested on 566 mammographic images consisting of 372 randomly selected scanned films from two public databases (mini-MIAS and DDSM), and 194 digital mammograms acquired with a GE Senographe 2000D FFDM system. A radiologist independently marked the centers of the nipples for evaluation of the results. The average error obtained was 6.7 mm (22 pixels) with reference to the center of the nipple as identified by the radiologist. Only two out of the 566 detected nipples (0.35 %) had an error larger than 50 mm. The method was also directly compared with two other techniques for the detection of the nipple. The results indicate that the proposed method outperforms other algorithms presented in the literature and can be used to identify accurately the nipple on various types of mammographic images.
Third-order aberrations in GRIN crystalline lens: A new method based on axial and field rays
Río, Arturo Díaz del; Gómez-Reino, Carlos; Flores-Arias, M. Teresa
2014-01-01
This paper presents a new procedure for calculating the third-order aberration of gradient-index (GRIN) lenses that combines an iterative numerical method with the Hamiltonian theory of aberrations in terms of two paraxial rays with boundary conditions on general curved end surfaces and, as a second algebraic step has been presented. Application of this new method to a GRIN human is analyzed in the framework of the bi-elliptical model. The different third-order aberrations are determined, except those that need for their calculation skew rays, because the study is made only for meridional rays. PMID:25444647
Third-order aberrations in GRIN crystalline lens: a new method based on axial and field rays.
Río, Arturo Díaz Del; Gómez-Reino, Carlos; Flores-Arias, M Teresa
2015-01-01
This paper presents a new procedure for calculating the third-order aberration of gradient-index (GRIN) lenses that combines an iterative numerical method with the Hamiltonian theory of aberrations in terms of two paraxial rays with boundary conditions on general curved end surfaces and, as a second algebraic step has been presented. Application of this new method to a GRIN human is analyzed in the framework of the bi-elliptical model. The different third-order aberrations are determined, except those that need for their calculation skew rays, because the study is made only for meridional rays. PMID:25444647
Third-order aberrations in GRIN crystalline lens: a new method based on axial and field rays.
Río, Arturo Díaz Del; Gómez-Reino, Carlos; Flores-Arias, M Teresa
2015-01-01
This paper presents a new procedure for calculating the third-order aberration of gradient-index (GRIN) lenses that combines an iterative numerical method with the Hamiltonian theory of aberrations in terms of two paraxial rays with boundary conditions on general curved end surfaces and, as a second algebraic step has been presented. Application of this new method to a GRIN human is analyzed in the framework of the bi-elliptical model. The different third-order aberrations are determined, except those that need for their calculation skew rays, because the study is made only for meridional rays.
Jiang, Su; Liu, Ya-Feng; Wang, Xiao-Min; Liu, Ke-Fei; Zhang, Ding-Hong; Li, Yi-Ding; Yu, Ai-Ping; Zhang, Xiao-Hui; Zhang, Jia-Yi; Xu, Jian-Guang; Gu, Yu-Dong; Xu, Wen-Dong; Zeng, Shao-Qun
2016-01-01
We introduce a more flexible optogenetics-based mapping system attached on a stereo microscope, which offers automatic light stimulation to individual regions of interest in the cortex that expresses light-activated channelrhodopsin-2 in vivo. Combining simultaneous recording of electromyography from specific forelimb muscles, we demonstrate that this system offers much better efficiency and precision in mapping distinct domains for controlling limb muscles in the mouse motor cortex. Furthermore, the compact and modular design of the system also yields a simple and flexible implementation to different commercial stereo microscopes, and thus could be widely used among laboratories.
Jiang, Su; Liu, Ya-Feng; Wang, Xiao-Min; Liu, Ke-Fei; Zhang, Ding-Hong; Li, Yi-Ding; Yu, Ai-Ping; Zhang, Xiao-Hui; Zhang, Jia-Yi; Xu, Jian-Guang; Gu, Yu-Dong; Xu, Wen-Dong; Zeng, Shao-Qun
2016-01-01
We introduce a more flexible optogenetics-based mapping system attached on a stereo microscope, which offers automatic light stimulation to individual regions of interest in the cortex that expresses light-activated channelrhodopsin-2 in vivo. Combining simultaneous recording of electromyography from specific forelimb muscles, we demonstrate that this system offers much better efficiency and precision in mapping distinct domains for controlling limb muscles in the mouse motor cortex. Furthermore, the compact and modular design of the system also yields a simple and flexible implementation to different commercial stereo microscopes, and thus could be widely used among laboratories. PMID:27699114
NASA Astrophysics Data System (ADS)
Cottura, M.; Appolaire, B.; Finel, A.; Le Bouar, Y.
2016-09-01
A phase field model is coupled to strain gradient crystal plasticity based on dislocation densities. The resulting model includes anisotropic plasticity and the size-dependence of plastic activity, required when plasticity is confined in region below few microns in size. These two features are important for handling microstructure evolutions during diffusive phase transformations that involve plastic deformation occurring in confined areas such as Ni-based superalloys undergoing rafting. The model also uses a storage-recovery law for the evolution of the dislocation density of each glide system and a hardening matrix to account for the short-range interactions between dislocations. First, it is shown that the unstable modes during the morphological destabilization of a growing misfitting circular precipitate are selected by the anisotropy of plasticity. Then, the rafting of γ‧ precipitates in a Ni-based superalloy is investigated during [100] creep loadings. Our model includes most of the important physical phenomena accounted for during the microstructure evolution, such as the presence of different crystallographic γ‧ variants, their misfit with the γ matrix, the elastic inhomogeneity and anisotropy, the hardening, anisotropy and viscosity of plasticity. In agreement with experiments, the model predicts that rafting proceeds perpendicularly to the tensile loading axis and it is shown that plasticity slows down significantly the evolution of the rafts.
NASA Astrophysics Data System (ADS)
Vergallo, P.; Lay-Ekuakille, A.
2013-08-01
Brain activity can be recorded by means of EEG (Electroencephalogram) electrodes placed on the scalp of the patient. The EEG reflects the activity of groups of neurons located in the head, and the fundamental problem in neurophysiology is the identification of the sources responsible of brain activity, especially if a seizure occurs and in this case it is important to identify it. The studies conducted in order to formalize the relationship between the electromagnetic activity in the head and the recording of the generated external field allow to know pattern of brain activity. The inverse problem, that is given the sampling field at different electrodes the underlying asset must be determined, is more difficult because the problem may not have a unique solution, or the search for the solution is made difficult by a low spatial resolution which may not allow to distinguish between activities involving sources close to each other. Thus, sources of interest may be obscured or not detected and known method in source localization problem as MUSIC (MUltiple SIgnal Classification) could fail. Many advanced source localization techniques achieve a best resolution by exploiting sparsity: if the number of sources is small as a result, the neural power vs. location is sparse. In this work a solution based on the spatial sparsity of the field signal is presented and analyzed to improve MUSIC method. For this purpose, it is necessary to set a priori information of the sparsity in the signal. The problem is formulated and solved using a regularization method as Tikhonov, which calculates a solution that is the better compromise between two cost functions to minimize, one related to the fitting of the data, and another concerning the maintenance of the sparsity of the signal. At the first, the method is tested on simulated EEG signals obtained by the solution of the forward problem. Relatively to the model considered for the head and brain sources, the result obtained allows to
NASA Astrophysics Data System (ADS)
Peng, Jiayuan; Zhang, Zhen; Wang, Jiazhou; Xie, Jiang; Chen, Junchao; Hu, Weigang
2015-10-01
GafChromic RTQA2 film is a type of radiochromic film designed for light field and radiation field alignment. The aim of this study is to extend the application of RTQA2 film to the measurement of patient specific quality assurance (QA) fields as a 2D relative dosimeter. Pre-irradiated and post-irradiated RTQA2 films were scanned in reflection mode using a flatbed scanner. A plan-based calibration (PBC) method utilized the mapping information of the calculated dose image and film grayscale image to create a dose versus pixel value calibration model. This model was used to calibrate the film grayscale image to the film relative dose image. The dose agreement between calculated and film dose images were analyzed by gamma analysis. To evaluate the feasibility of this method, eight clinically approved RapidArc cases (one abdomen cancer and seven head-and-neck cancer patients) were tested using this method. Moreover, three MLC gap errors and two MLC transmission errors were introduced to eight Rapidarc cases respectively to test the robustness of this method. The PBC method could overcome the film lot and post-exposure time variations of RTQA2 film to get a good 2D relative dose calibration result. The mean gamma passing rate of eight patients was 97.90% ± 1.7%, which showed good dose consistency between calculated and film dose images. In the error test, the PBC method could over-calibrate the film, which means some dose error in the film would be falsely corrected to keep the dose in film consistent with the dose in the calculated dose image. This would then lead to a false negative result in the gamma analysis. In these cases, the derivative curve of the dose calibration curve would be non-monotonic which would expose the dose abnormality. By using the PBC method, we extended the application of more economical RTQA2 film to patient specific QA. The robustness of the PBC method has been improved by analyzing the monotonicity of the derivative of the
NASA Astrophysics Data System (ADS)
Shackleton, J. R.; Cooke, M. L.; Johnson, G.; Cilona, A.
2012-12-01
latest stages of fold growth during or after deposition of terrestrial deposits (Garumnian sequence). This interpretation is based on the observation of significant iron oxidation that is probably associated with subaerial exposure. Sant Corneli anticline offers a unique opportunity to evaluate the efficacy of structural restoration in predicting sub-seismic scale fractures and faults because each fracturing event is temporally constrained by relationships to growth strata that constrain fold evolution. Thus, the strains predicted by the restorations are compared to the fracture sets that formed over the corresponding time intervals. In this manner, we can directly evaluate the efficacy of the restoration in predicting fracture patterns, although the time intervals identified by the growth strata are typically much larger than the time scales we expect individual fracturing events to occur.
NASA Astrophysics Data System (ADS)
Kitada, K.; Araki, E.; Kimura, T.; Saffer, D. M.; Byrne, T.; McNeill, L. C.; Toczko, S.; Eguchi, N. O.; Takahashi, K.
2009-12-01
environmental conditions, such as shock, acceleration, and vibration during installation; and (2) to confirm sensor installation operational procedures, such as onboard assembly of the sensor tree, ship maneuvers to reenter the sensor tree, and entry into the hole. Acceleration and tilt data were recorded at 500 Hz and recovered after the dummy run test. Preliminary results from vibration analysis show that the strong vibration due to the high Kuroshio Current (~5 knot) occurred during the test. Spectral analysis of the collected acceleration data represents the drill pipe vibration and resonance of the instrument carrier. The resonance was much larger than the drill pipe vibration and its magnitude may depend on the structure of the instrument carrier. Preliminary results of the vibration mode, its amplitude, and comparison with current speed and direction, ships speed and depth of the sensor assembly are also shown to elucidate the cause of the vibration. These results give us an opportunity to establish installation methods, and to develop and refine sensors for the future long-term observatory emplacement.
Low Field Squid MRI Devices, Components and Methods
NASA Technical Reports Server (NTRS)
Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor); Hahn, Inseob (Inventor)
2014-01-01
Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.
Low field SQUID MRI devices, components and methods
NASA Technical Reports Server (NTRS)
Penanen, Konstantin I. (Inventor); Eom, Byeong H (Inventor); Hahn, Inseob (Inventor)
2010-01-01
Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.
Low Field Squid MRI Devices, Components and Methods
NASA Technical Reports Server (NTRS)
Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor); Hahn, Inseob (Inventor)
2013-01-01
Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.
Low field SQUID MRI devices, components and methods
NASA Technical Reports Server (NTRS)
Penanen, Konstantin I. (Inventor); Eom, Byeong H. (Inventor); Hahn, Inseob (Inventor)
2011-01-01
Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.
Kim, Dae-Kyu; Oh, Jeong-Do; Shin, Eun-Sol; Seo, Hoon-Seok; Choi, Jong-Ho
2014-04-28
The neutral cluster beam deposition (NCBD) method has been applied to the production and characterization of ambipolar, heterojunction-based organic light-emitting field-effect transistors (OLEFETs) with a top-contact, multi-digitated, long-channel geometry. Organic thin films of n-type N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide and p-type copper phthalocyanine were successively deposited on the hydroxyl-free polymethyl-methacrylate (PMMA)-coated SiO{sub 2} dielectrics using the NCBD method. Characterization of the morphological and structural properties of the organic active layers was performed using atomic force microscopy and X-ray diffraction. Various device parameters such as hole- and electron-carrier mobilities, threshold voltages, and electroluminescence (EL) were derived from the fits of the observed current-voltage and current-voltage-light emission characteristics of OLEFETs. The OLEFETs demonstrated good field-effect characteristics, well-balanced ambipolarity, and substantial EL under ambient conditions. The device performance, which is strongly correlated with the surface morphology and the structural properties of the organic active layers, is discussed along with the operating conduction mechanism.
NASA Astrophysics Data System (ADS)
Maris, Virginie
An existing 3-D magnetotelluric (MT) inversion program written for a single processor personal computer (PC) has been modified and parallelized using OpenMP, in order to run the program efficiently on a multicore workstation. The program uses the Gauss-Newton inversion algorithm based on a staggered-grid finite-difference forward problem, requiring explicit calculation of the Frechet derivatives. The most time-consuming tasks are calculating the derivatives and determining the model parameters at each iteration. Forward modeling and derivative calculations are parallelized by assigning the calculations for each frequency to separate threads, which execute concurrently. Model parameters are obtained by factoring the Hessian using the LDLT method, implemented using a block-cyclic algorithm and compact storage. MT data from 102 tensor stations over the East Flank of the Coso Geothermal Field, California are inverted. Less than three days are required to invert the dataset for ˜ 55,000 inversion parameters on a 2.66 GHz 8-CPU PC with 16 GB of RAM. Inversion results, recovered from a halfspace rather than initial 2-D inversions, qualitatively resemble models from massively parallel 3-D inversion by other researchers and overall, exhibit an improved fit. A steeply west-dipping conductor under the western East Flank is tentatively correlated with a zone of high-temperature ionic fluids based on known well production and lost circulation intervals. Beneath the Main Field, vertical and north-trending shallow conductors are correlated with geothermal producing intervals as well.
Harris, W; Zhang, Y; Ren, L; Yin, F
2014-06-01
Purpose: To investigate the feasibility of using nanoparticle markers to validate liver tumor motion together with a deformation field map-based four dimensional (4D) cone-beam computed tomography (CBCT) reconstruction method. Methods: A technique for lung 4D-CBCT reconstruction has been previously developed using a deformation field map (DFM)-based strategy. In this method, each phase of the 4D-CBCT is considered as a deformation of a prior CT volume. The DFM is solved by a motion modeling and free-form deformation (MM-FD) technique, using a data fidelity constraint and the deformation energy minimization. For liver imaging, there is low contrast of a liver tumor in on-board projections. A validation of liver tumor motion using implanted gold nanoparticles, along with the MM-FD deformation technique is implemented to reconstruct onboard 4D CBCT liver radiotherapy images. These nanoparticles were placed around the liver tumor to reflect the tumor positions in both CT simulation and on-board image acquisition. When reconstructing each phase of the 4D-CBCT, the migrations of the gold nanoparticles act as a constraint to regularize the deformation field, along with the data fidelity and the energy minimization constraints. In this study, multiple tumor diameters and positions were simulated within the liver for on-board 4D-CBCT imaging. The on-board 4D-CBCT reconstructed by the proposed method was compared with the “ground truth” image. Results: The preliminary data, which uses reconstruction for lung radiotherapy suggests that the advanced reconstruction algorithm including the gold nanoparticle constraint will Resultin volume percentage differences (VPD) between lesions in reconstructed images by MM-FD and “ground truth” on-board images of 11.5% (± 9.4%) and a center of mass shift of 1.3 mm (± 1.3 mm) for liver radiotherapy. Conclusion: The advanced MM-FD technique enforcing the additional constraints from gold nanoparticles, results in improved accuracy
NASA Astrophysics Data System (ADS)
Zaccheo, T. S.; Pernini, T.; Botos, C.; Dobler, J. T.; Blume, N.
2015-12-01
The Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE) combines real-time differential Laser Absorption Spectroscopy (LAS) measurements with a lightweight web-based data acquisition and product generation system to provide autonomous 24/7 monitoring of CO2. The current GreenLITE system is comprised of two transceivers and a series of retro-reflectors that continuously measure the differential transmission over a user-defined set of intersecting line-of-site paths or "chords" that form the plane of interest. These observations are first combined with in situ surface measurements of temperature (T), pressure (P) and relative humidity (RH) to compute the integrated CO2 mixing ratios based on an iterative radiative transfer modeling approach. The retrieved CO2 mixing ratios are then grouped based on observation time and employed in a sparse sample reconstruction method to provide a tomographic- like representation of the 2-D distribution of CO2 over the field of interest. This reconstruction technique defines the field of interest as a set of idealized plumes whose integrated values best match the observations. The GreenLITE system has been deployed at two primary locations; 1) the Zero Emissions Research and Technology (ZERT) center in Bozeman, Montana, in Aug-Sept 2014, where more than 200 hours of data were collected over a wide range of environmental conditions while utilizing a controlled release of CO2 into a segmented underground pipe, and 2) continuously at a carbon sequestration test facility in Feb-Aug 2015. The system demonstrated the ability to identify persistent CO2 sources at the ZERT test facility and showed strong correlation with an independent measurement using a LI-COR based system. Here we describe the measurement approach, algorithm design and extended study results.
Pla, Maria; La Paz, José-Luis; Peñas, Gisela; García, Nora; Palaudelmàs, Montserrat; Esteve, Teresa; Messeguer, Joaquima; Melé, Enric
2006-04-01
Maize is one of the main crops worldwide and an increasing number of genetically modified (GM) maize varieties are cultivated and commercialized in many countries in parallel to conventional crops. Given the labeling rules established e.g. in the European Union and the necessary coexistence between GM and non-GM crops, it is important to determine the extent of pollen dissemination from transgenic maize to other cultivars under field conditions. The most widely used methods for quantitative detection of GMO are based on real-time PCR, which implies the results are expressed in genome percentages (in contrast to seed or grain percentages). Our objective was to assess the accuracy of real-time PCR based assays to accurately quantify the contents of transgenic grains in non-GM fields in comparison with the real cross-fertilization rate as determined by phenotypical analysis. We performed this study in a region where both GM and conventional maize are normally cultivated and used the predominant transgenic maize Mon810 in combination with a conventional maize variety which displays the characteristic of white grains (therefore allowing cross-pollination quantification as percentage of yellow grains). Our results indicated an excellent correlation between real-time PCR results and number of cross-fertilized grains at Mon810 levels of 0.1-10%. In contrast, Mon810 percentage estimated by weight of grains produced less accurate results. Finally, we present and discuss the pattern of pollen-mediated gene flow from GM to conventional maize in an example case under field conditions. PMID:16604462
Pla, Maria; La Paz, José-Luis; Peñas, Gisela; García, Nora; Palaudelmàs, Montserrat; Esteve, Teresa; Messeguer, Joaquima; Melé, Enric
2006-04-01
Maize is one of the main crops worldwide and an increasing number of genetically modified (GM) maize varieties are cultivated and commercialized in many countries in parallel to conventional crops. Given the labeling rules established e.g. in the European Union and the necessary coexistence between GM and non-GM crops, it is important to determine the extent of pollen dissemination from transgenic maize to other cultivars under field conditions. The most widely used methods for quantitative detection of GMO are based on real-time PCR, which implies the results are expressed in genome percentages (in contrast to seed or grain percentages). Our objective was to assess the accuracy of real-time PCR based assays to accurately quantify the contents of transgenic grains in non-GM fields in comparison with the real cross-fertilization rate as determined by phenotypical analysis. We performed this study in a region where both GM and conventional maize are normally cultivated and used the predominant transgenic maize Mon810 in combination with a conventional maize variety which displays the characteristic of white grains (therefore allowing cross-pollination quantification as percentage of yellow grains). Our results indicated an excellent correlation between real-time PCR results and number of cross-fertilized grains at Mon810 levels of 0.1-10%. In contrast, Mon810 percentage estimated by weight of grains produced less accurate results. Finally, we present and discuss the pattern of pollen-mediated gene flow from GM to conventional maize in an example case under field conditions.
Tiwari, Shashi; Balasubramanian, S. K.; Takashima, Wataru; Nagamatsu, S.; Prakash, Rajiv
2014-09-07
A comparative study on electrical performance, optical properties, and surface morphology of poly(3-hexylthiophene) (P3HT) and P3HT-nanofibers based “normally on” type p-channel field effect transistors (FETs), fabricated by two different coating techniques has been reported here. Nanofibers are prepared in the laboratory with the approach of self-assembly of P3HT molecules into nanofibers in an appropriate solvent. P3HT (0.3 wt. %) and P3HT-nanofibers (∼0.25 wt. %) are used as semiconductor transport materials for deposition over FETs channel through spin coating as well as through our recently developed floating film transfer method (FTM). FETs fabricated using FTM show superior performance compared to spin coated devices; however, the mobility of FTM films based FETs is comparable to the mobility of spin coated one. The devices based on P3HT-nanofibers (using both the techniques) show much better performance in comparison to P3HT FETs. The best performance among all the fabricated organic field effect transistors are observed for FTM coated P3HT-nanofibers FETs. This improved performance of nanofiber-FETs is due to ordering of fibers and also due to the fact that fibers offer excellent charge transport facility because of point to point transmission. The optical properties and structural morphologies (P3HT and P3HT-nanofibers) are studied using UV-visible absorption spectrophotometer and atomic force microscopy , respectively. Coating techniques and effect of fiber formation for organic conductors give information for fabrication of organic devices with improved performance.
Historic Methods for Capturing Magnetic Field Images
ERIC Educational Resources Information Center
Kwan, Alistair
2016-01-01
I investigated two late 19th-century methods for capturing magnetic field images from iron filings for historical insight into the pedagogy of hands-on physics education methods, and to flesh out teaching and learning practicalities tacit in the historical record. Both methods offer opportunities for close sensory engagement in data-collection…
Historic Methods for Capturing Magnetic Field Images
NASA Astrophysics Data System (ADS)
Kwan, Alistair
2016-03-01
I investigated two late 19th-century methods for capturing magnetic field images from iron filings for historical insight into the pedagogy of hands-on physics education methods, and to flesh out teaching and learning practicalities tacit in the historical record. Both methods offer opportunities for close sensory engagement in data-collection processes.
Magnetic space-based field measurements
NASA Technical Reports Server (NTRS)
Langel, R. A.
1981-01-01
Satellite measurements of the geomagnetic field began with the launch of Sputnik 3 in May 1958 and have continued sporadically in the intervening years. A list of spacecraft that have made significant contributions to an understanding of the near-earth geomagnetic field is presented. A new era in near-earth magnetic field measurements began with NASA's launch of Magsat in October 1979. Attention is given to geomagnetic field modeling, crustal magnetic anomaly studies, and investigations of the inner earth. It is concluded that satellite-based magnetic field measurements make global surveys practical for both field modeling and for the mapping of large-scale crustal anomalies. They are the only practical method of accurately modeling the global secular variation. Magsat is providing a significant contribution, both because of the timeliness of the survey and because its vector measurement capability represents an advance in the technology of such measurements.
NASA Astrophysics Data System (ADS)
Revel, G. M.; Martarelli, M.; Chiariotti, P.
2010-07-01
The selective intensity technique is a powerful tool for the localization of acoustic sources and for the identification of the structural contribution to the acoustic emission. In practice, the selective intensity method is based on simultaneous measurements of acoustic intensity, by means of a couple of matched microphones, and structural vibration of the emitting object. In this paper high spatial density multi-point vibration data, acquired by using a scanning laser Doppler vibrometer, have been used for the first time. Therefore, by applying the selective intensity algorithm, the contribution of a large number of structural sources to the acoustic field radiated by the vibrating object can be estimated. The selective intensity represents the distribution of the acoustic monopole sources on the emitting surface, as if each monopole acted separately from the others. This innovative selective intensity approach can be very helpful when the measurement is performed on large panels in highly reverberating environments, such as aircraft cabins. In this case the separation of the direct acoustic field (radiated by the vibrating panels of the fuselage) and the reverberant one is difficult by traditional techniques. The work shown in this paper is the application of part of the results of the European project CREDO (Cabin Noise Reduction by Experimental and Numerical Design Optimization) carried out within the framework of the EU. Therefore the aim of this paper is to illustrate a real application of the method to the interior acoustic characterization of an Alenia Aeronautica ATR42 ground test facility, Alenia Aeronautica being a partner of the CREDO project.
NASA Astrophysics Data System (ADS)
Lee, Dong-Ju; Woo, Jung-Hyun; Kim, Sa-Ung; Oh, Je-Seung; Yoo, Jeong-Hoon; Park, No-Cheol; Park, Young-Pil; Shimano, Takeshi; Nakamura, Shigeo
2007-06-01
In this paper, we propose an “L-shaped” rotary voice coil motor (VCM) actuator for an ultra slim optical disk drive (ODD) with a CF II card size using the integrated design method that integrates coupled-field analysis and design methods.
Human Biology, A Guide to Field Methods.
ERIC Educational Resources Information Center
Weiner, J. S.; Lourie, J. A.
The aim of this handbook is to provide, in a form suitable for use in the field, instructions on the whole range of methods required for the fulfillment of human biological studies on a comparative basis. Certain of these methods can be used to carry out the rapid surveys on growth, physique, and genetic constitution. They are also appropriate for…
Soil Identification using Field Electrical Resistivity Method
NASA Astrophysics Data System (ADS)
Hazreek, Z. A. M.; Rosli, S.; Chitral, W. D.; Fauziah, A.; Azhar, A. T. S.; Aziman, M.; Ismail, B.
2015-06-01
Geotechnical site investigation with particular reference to soil identification was important in civil engineering works since it reports the soil condition in order to relate the design and construction of the proposed works. In the past, electrical resistivity method (ERM) has widely being used in soil characterization but experienced several black boxes which related to its results and interpretations. Hence, this study performed a field electrical resistivity method (ERM) using ABEM SAS (4000) at two different types of soils (Gravelly SAND and Silty SAND) in order to discover the behavior of electrical resistivity values (ERV) with type of soils studied. Soil basic physical properties was determine thru density (p), moisture content (w) and particle size distribution (d) in order to verify the ERV obtained from each type of soil investigated. It was found that the ERV of Gravelly SAND (278 Ωm & 285 Ωm) was slightly higher than SiltySAND (223 Ωm & 199 Ωm) due to the uncertainties nature of soils. This finding has showed that the results obtained from ERM need to be interpreted based on strong supported findings such as using direct test from soil laboratory data. Furthermore, this study was able to prove that the ERM can be established as an alternative tool in soil identification provided it was being verified thru other relevance information such as using geotechnical properties.
Method for making field-structured memory materials
Martin, James E.; Anderson, Robert A.; Tigges, Chris P.
2002-01-01
A method of forming a dual-level memory material using field structured materials. The field structured materials are formed from a dispersion of ferromagnetic particles in a polymerizable liquid medium, such as a urethane acrylate-based photopolymer, which are applied as a film to a support and then exposed in selected portions of the film to an applied magnetic or electric field. The field can be applied either uniaxially or biaxially at field strengths up to 150 G or higher to form the field structured materials. After polymerizing the field-structure materials, a magnetic field can be applied to selected portions of the polymerized field-structured material to yield a dual-level memory material on the support, wherein the dual-level memory material supports read-and-write binary data memory and write once, read many memory.
NASA Astrophysics Data System (ADS)
Ferreira, Vagner G.; Montecino, Henry D. C.; Yakubu, Caleb I.; Heck, Bernhard
2016-01-01
Currently, various satellite processing centers produce extensive data, with different solutions of the same field being available. For instance, the Gravity Recovery and Climate Experiment (GRACE) has been monitoring terrestrial water storage (TWS) since April 2002, while the Center for Space Research (CSR), the Jet Propulsion Laboratory (JPL), the GeoForschungsZentrum (GFZ), and the Groupe de Recherche de Géodésie Spatiale (GRGS) provide individual monthly solutions in the form of Stokes coefficients. The inverted TWS maps (or the regionally averaged values) from these coefficients are being used in many applications; however, as no ground truth data exist, the uncertainties are unknown. Consequently, the purpose of this work is to assess the quality of each processing center by estimating their uncertainties using a generalized formulation of the three-cornered hat (TCH) method. Overall, the TCH results for the study period of August 2002 to June 2014 indicate that at a global scale, the CSR, GFZ, GRGS, and JPL presented uncertainties of 9.4, 13.7, 14.8, and 13.2 mm, respectively. At a basin scale, the overall good performance of the CSR was observed at 91 river basins. The TCH-based results were confirmed by a comparison with an ensemble solution from the four GRACE processing centers.
Constantinou, Marios; Stolojan, Vlad; Rajeev, Kiron Prabha; Hinder, Steven; Fisher, Brett; Bogart, Timothy D; Korgel, Brian A; Shkunov, Maxim
2015-10-14
In this letter, we demonstrate a solution-based method for a one-step deposition and surface passivation of the as-grown silicon nanowires (Si NWs). Using N,N-dimethylformamide (DMF) as a mild oxidizing agent, the NWs' surface traps density was reduced by over 2 orders of magnitude from 1×10(13) cm(-2) in pristine NWs to 3.7×10(10) cm(-2) in DMF-treated NWs, leading to a dramatic hysteresis reduction in NW field-effect transistors (FETs) from up to 32 V to a near-zero hysteresis. The change of the polyphenylsilane NW shell stoichiometric composition was confirmed by X-ray photoelectron spectroscopy analysis showing a 35% increase in fully oxidized Si4+ species for DMF-treated NWs compared to dry NW powder. Additionally, a shell oxidation effect induced by DMF resulted is a more stable NW FET performance with steady transistor currents and only 1.5 V hysteresis after 1000 h of air exposure. PMID:26402417
Constantinou, Marios; Stolojan, Vlad; Rajeev, Kiron Prabha; Hinder, Steven; Fisher, Brett; Bogart, Timothy D; Korgel, Brian A; Shkunov, Maxim
2015-10-14
In this letter, we demonstrate a solution-based method for a one-step deposition and surface passivation of the as-grown silicon nanowires (Si NWs). Using N,N-dimethylformamide (DMF) as a mild oxidizing agent, the NWs' surface traps density was reduced by over 2 orders of magnitude from 1×10(13) cm(-2) in pristine NWs to 3.7×10(10) cm(-2) in DMF-treated NWs, leading to a dramatic hysteresis reduction in NW field-effect transistors (FETs) from up to 32 V to a near-zero hysteresis. The change of the polyphenylsilane NW shell stoichiometric composition was confirmed by X-ray photoelectron spectroscopy analysis showing a 35% increase in fully oxidized Si4+ species for DMF-treated NWs compared to dry NW powder. Additionally, a shell oxidation effect induced by DMF resulted is a more stable NW FET performance with steady transistor currents and only 1.5 V hysteresis after 1000 h of air exposure.
NASA Astrophysics Data System (ADS)
Ferreira, Vagner G.; Montecino, Henry D. C.; Yakubu, Caleb I.; Heck, Bernhard
2016-01-01
Currently, various satellite processing centers produce extensive data, with different solutions of the same field being available. For instance, the Gravity Recovery and Climate Experiment (GRACE) has been monitoring terrestrial water storage (TWS) since April 2002, while the Center for Space Research (CSR), the Jet Propulsion Laboratory (JPL), the GeoForschungsZentrum (GFZ), and the Groupe de Recherche de Géodésie Spatiale (GRGS) provide individual monthly solutions in the form of Stokes coefficients. The inverted TWS maps (or the regionally averaged values) from these coefficients are being used in many applications; however, as no ground truth data exist, the uncertainties are unknown. Consequently, the purpose of this work is to assess the quality of each processing center by estimating their uncertainties using a generalized formulation of the three-cornered hat (TCH) method. Overall, the TCH results for the study period of August 2002 to June 2014 indicate that at a global scale, the CSR, GFZ, GRGS, and JPL presented uncertainties of 9.4, 13.7, 14.8, and 13.2 mm, respectively. At a basin scale, the overall good performance of the CSR was observed at 91 river basins. The TCH-based results were confirmed by a comparison with an ensemble solution from the four GRACE processing centers.
Crozier, S; Liu, F; Wei, Q
2004-01-01
This paper evaluates a low-frequency FDTD method applied to the problem of induced E-fields/eddy currents in the human body resulting from the pulsed magnetic field gradients in MRI. In this algorithm, a distributed equivalent magnetic current (DEMC) is proposed as the electromagnetic source and is obtained by quasistatic calculation of the empty coil's vector potential or measurements therein. This technique circumvents the discretizing of complicated gradient coil geometries into a mesh of Yee cells, and thereby enables any type of gradient coil modeling or other complex low frequency sources. The proposed method has been verified against an example with an analytical solution. Results are presented showing the spatial distribution of gradient-induced electric fields in a multilayered spherical phantom model and a complete body model.
Zhang, Xiao-Yu; Yu, Xiao-Xia; Yu, Zhuo; Xue, Yu-Feng; Qi, Li-Peng
2014-06-01
A two-step method was developed to evaluate potato resistance to black scurf caused by Rhizoctonia solani. Tuber piece inoculum was first conducted in the laboratory, which was also first reported in this study. After inoculation with pathogen discs and culture for 48 h, the necrotic spots on the inoculated potato pieces were generated and measured by the crossing method. Further evaluation was conducted through field experiments using a wheat bran inoculum method. The wheat bran inoculum was placed into the pit dispersedly and surrounded seed tubers. Each cultivar or line was subjected to five treatments of 0-, 2-, 3-, 4-, and 5-g soil inoculum. The results showed that 2-4 g of wheat bran inoculum was the optimum for identifying tuber black scurf resistance. The laboratory scores positively correlated with the incidence and severity of black scurf in the field. According to the results in the laboratory, relatively resistant cultivars could be selected for further estimation of tuber black scurf resistance in field experiments. It is a practical and effective screening method for rapid identification of resistant potato germplasm, which can reduce workload in the field, shorten time required for identification.
ERIC Educational Resources Information Center
Napier, John D.; Vansickle, Ronald L.
1978-01-01
Comparison of pre-service social studies teachers in field and non-field based methods courses indicated no significant differences with regard to teaching skills, attitudes, or behaviors teachers should exhibit in the classroom. (Author/DB)
Physicochemical methods for enhancing oil recovery from oil fields
NASA Astrophysics Data System (ADS)
Altunina, L. K.; Kuvshinov, V. A.
2007-10-01
Physicochemical methods for enhancing oil recovery from oil fields that are developed using water flooding and thermal steam treatment are considered. The results of pilot testing of processes based on these methods carried out at West Siberian and Chinese oil fields are analysed. The attention is focused on the processes that make use of surfactant blends and alkaline buffer solutions and thermotropic gel-forming systems.
A method for characterizing photon radiation fields
Whicker, J.J.; Hsu, H.H.; Hsieh, F.H.; Borak, T.B.
1999-04-01
Uncertainty in dosimetric and exposure rate measurements can increase in areas where multi-directional and low-energy photons (< 100 keV) exist because of variations in energy and angular measurement response. Also, accurate measurement of external exposures in spatially non-uniform fields may require multiple dosimetry. Therefore, knowledge of the photon fields in the workplace is required for full understanding of the accuracy of dosimeters and instruments, and for determining the need for multiple dosimeters. This project was designed to develop methods to characterize photon radiation fields in the workplace, and to test the methods in a plutonium facility. The photon field at selected work locations was characterized using TLDs and a collimated NaI(Tl) detector from which spatial variations in photon energy distributions were calculated from measured spectra. Laboratory results showed the accuracy and utility of the method. Field measurement results combined with observed work patterns suggested the following: (1) workers are exposed from all directions, but not isotropically, (2) photon energy distributions were directionally dependent, (3) stuffing nearby gloves into the glovebox reduced exposure rates significantly, (4) dosimeter placement on the front of the chest provided for a reasonable estimate of the average dose equivalent to workers` torsos, (5) justifiable conclusions regarding the need for multiple dosimetry can be made using this quantitative method, and (6) measurements of the exposure rates with ionization chambers pointed with open beta windows toward the glovebox provided the highest measured rates, although absolute accuracy of the field measurements still needs to be assessed.
Got Mud? Field-based Learning in Wetland Ecology.
ERIC Educational Resources Information Center
Baldwin, Andrew H.
2001-01-01
Describes methods for teaching wetland ecology classes based mainly on direct, hands-on field experiences for students. Makes the case that classroom lectures are necessary but there is no substitute for field and laboratory experiences. (Author/MM)
Electric Field Quantitative Measurement System and Method
NASA Technical Reports Server (NTRS)
Generazio, Edward R. (Inventor)
2016-01-01
A method and system are provided for making a quantitative measurement of an electric field. A plurality of antennas separated from one another by known distances are arrayed in a region that extends in at least one dimension. A voltage difference between at least one selected pair of antennas is measured. Each voltage difference is divided by the known distance associated with the selected pair of antennas corresponding thereto to generate a resulting quantity. The plurality of resulting quantities defined over the region quantitatively describe an electric field therein.
A New Method for Coronal Magnetic Field Reconstruction
NASA Astrophysics Data System (ADS)
Yi, Sibaek; Choe, Gwangson; Lim, Daye
2015-08-01
We present a new, simple, variational method for reconstruction of coronal force-free magnetic fields based on vector magnetogram data. Our method employs vector potentials for magnetic field description in order to ensure the divergence-free condition. As boundary conditions, it only requires the normal components of magnetic field and current density so that the boundary conditions are not over-specified as in many other methods. The boundary normal current distribution is initially fixed once and for all and does not need continual adjustment as in stress-and-relax type methods. We have tested the computational code based on our new method in problems with known solutions and those with actual photospheric data. When solutions are fully given at all boundaries, the accuracy of our method is almost comparable to best performing methods in the market. When magnetic field data are given only at the photospheric boundary, our method excels other methods in most “figures of merit” devised by Schrijver et al. (2006). Furthermore the residual force in the solution is at least an order of magnitude smaller than that of any other method. It can also accommodate the source-surface boundary condition at the top boundary. Our method is expected to contribute to the real time monitoring of the sun required for future space weather forecasts.
Ding, Cheng; Chen, Tianming; Li, Zhaoxia; Yan, Jinlong
2015-05-01
Using the standardized polyurethane foam unit (PFU) method, a preliminary investigation was carried out on the bioaccumulation and the ecotoxic effects of the pulp and paper wastewater for irrigating reed fields. Static ectoxicity test had shown protozoal communities were very sensitive to variations in toxin time and effective concentration (EC) of the pulp and paper wastewater. Shannon-Wiener diversity index (H) was a more suitable indicator of the extent of water pollution than Gleason and Margalef diversity index (d), Simpson's diversity index (D), and Pielou's index (J). The regression equation between S eq and EC was S eq = - 0.118EC + 18.554. The relatively safe concentration and maximum acceptable toxicant concentration (MATC) of the wastewater for the protozoal communities were about 20 % and 42 %, respectively. To safely use this wastewater for irrigation, more than 58 % of the toxins must be removed or diluted by further processing. Monitoring of the wastewater in representative irrigated reed fields showed that the regularity of the protozoal colonization process was similar to the static ectoxicity, indicating that the toxicity of the irrigating pulp and paper wastewater was not lethal to protozoal communities in the reed fields. This study demonstrated the applicability of the PFU method in monitoring the ecotoxic effects of pulp and paper wastewater on the level of microbial communities and may guide the supervision and control of pulp and paper wastewater irrigating within the reed fields ecological system (RFES).
Fibre based integral field unit constructional techniques
NASA Astrophysics Data System (ADS)
Murray, Graham J.
2006-06-01
Presented here is a selected overview of constructional techniques and principles that have been developed and implemented at the University of Durham in the manufacture of successful fibre-based integral field units. The information contained herein is specifically intended to highlight the constructional methods that have been devised to assemble an efficient fibre bundle. Potential pitfalls that need to be considered when embarking upon such a deceptively simple instrument are also discussed.
Baryons in the Field Correlator Method
Kezerashvili, R. Ya.; Narodetskii, I. M.; Veselov, A. I.
2009-12-17
The ground and P-wave excited states of nnn, nns and ssn baryons are studied in the framework of the field correlator method using the running strong coupling constant in the Coulomb-like part of the three-quark potential. The string correction for the confinement potential of the orbitally excited baryons, which is the leading contribution of the proper inertia of the rotating strings, is estimated.
A field day of soil regulation methods
NASA Astrophysics Data System (ADS)
Kempter, Axel; Kempter, Carmen
2015-04-01
The subject Soil plays an important role in the school subject geography. In particular in the upper classes it is expected that the knowledge from the area of Soil can be also be applied in other subjects. Thus, e.g., an assessment of economy and agricultural development and developing potential requires the interweaving of natural- geographic and human-geographic factors. The treatment of the subject Soil requires the desegregation of the results of different fields like Physics, Chemistry and Biology. Accordingly the subject gives cause to professional-covering lessons and offers the opportunity for practical work as well as excursions. Beside the mediation of specialist knowledge and with the support of the methods and action competences, the independent learning and the practical work should have a special emphasis on the field excursion by using stimulating exercises oriented to solving problems and mastering the methods. This aim should be achieved by the interdisciplinary treatment of the subject Soil in the task-oriented learning process on the field day. The methods and experiments should be sensibly selected for both the temporal and material supply constraints. During the field day the pupils had to categorize soil texture, soil colour, soil profile, soil skeleton, lime content, ion exchanger (Soils filter materials), pH-Value, water retention capacity and evidence of different ions like e.g. Fe3+, Mg2+, Cl- and NO3-. The pupils worked on stations and evaluated the data to receive a general view of the ground at the end. According to numbers of locations, amount of time and group size, different procedures can be offered. There are groups of experts who carry out the same experiment at all locations and split for the evaluation in different groups or each group ran through all stations. The results were compared and discussed at the end.
Tahmasebi Birgani, Mohamad J.; Chegeni, Nahid; Zabihzadeh, Mansoor; Hamzian, Nima
2014-04-01
Equivalent field is frequently used for central axis depth-dose calculations of rectangular- and irregular-shaped photon beams. As most of the proposed models to calculate the equivalent square field are dosimetry based, a simple physical-based method to calculate the equivalent square field size was used as the basis of this study. The table of the sides of the equivalent square or rectangular fields was constructed and then compared with the well-known tables by BJR and Venselaar, et al. with the average relative error percentage of 2.5 ± 2.5% and 1.5 ± 1.5%, respectively. To evaluate the accuracy of this method, the percentage depth doses (PDDs) were measured for some special irregular symmetric and asymmetric treatment fields and their equivalent squares for Siemens Primus Plus linear accelerator for both energies, 6 and 18 MV. The mean relative differences of PDDs measurement for these fields and their equivalent square was approximately 1% or less. As a result, this method can be employed to calculate equivalent field not only for rectangular fields but also for any irregular symmetric or asymmetric field.
Improved methods for fan sound field determination
NASA Technical Reports Server (NTRS)
Cicon, D. E.; Sofrin, T. G.; Mathews, D. C.
1981-01-01
Several methods for determining acoustic mode structure in aircraft turbofan engines using wall microphone data were studied. A method for reducing data was devised and implemented which makes the definition of discrete coherent sound fields measured in the presence of engine speed fluctuation more accurate. For the analytical methods, algorithms were developed to define the dominant circumferential modes from full and partial circumferential arrays of microphones. Axial arrays were explored to define mode structure as a function of cutoff ratio, and the use of data taken at several constant speeds was also evaluated in an attempt to reduce instrumentation requirements. Sensitivities of the various methods to microphone density, array size and measurement error were evaluated and results of these studies showed these new methods to be impractical. The data reduction method used to reduce the effects of engine speed variation consisted of an electronic circuit which windowed the data so that signal enhancement could occur only when the speed was within a narrow range.
Ogura, Toshihiko
2014-08-08
Highlights: • We developed a high-sensitive frequency transmission electric-field (FTE) system. • The output signal was highly enhanced by applying voltage to a metal layer on SiN. • The spatial resolution of new FTE method is 41 nm. • New FTE system enables observation of the intact bacteria and virus in water. - Abstract: The high-resolution structural analysis of biological specimens by scanning electron microscopy (SEM) presents several advantages. Until now, wet bacterial specimens have been examined using atmospheric sample holders. However, images of unstained specimens in water using these holders exhibit very poor contrast and heavy radiation damage. Recently, we developed the frequency transmission electric-field (FTE) method, which facilitates the SEM observation of biological specimens in water without radiation damage. However, the signal detection system presents low sensitivity. Therefore, a high EB current is required to generate clear images, and thus reducing spatial resolution and inducing thermal damage to the samples. Here a high-sensitivity detection system is developed for the FTE method, which enhances the output signal amplitude by hundredfold. The detection signal was highly enhanced when voltage was applied to the metal layer on silicon nitride thin film. This enhancement reduced the EB current and improved the spatial resolution as well as the signal-to-noise ratio. The spatial resolution of a high-sensitive FTE system is 41 nm, which is considerably higher than previous FTE system. New FTE system can easily be utilised to examine various unstained biological specimens in water, such as living bacteria and viruses.
Duality relations in the auxiliary field method
Silvestre-Brac, Bernard
2011-05-15
The eigenenergies {epsilon}{sup (N)}(m;{l_brace}n{sub i}, l{sub i{r_brace}}) of a system of N identical particles with a mass m are functions of the various radial quantum numbers n{sub i} and orbital quantum numbers l{sub i}. Approximations E{sup (N)}(m;Q) of these eigenenergies, depending on a principal quantum number Q({l_brace}n{sub i}, l{sub i{r_brace}}), can be obtained in the framework of the auxiliary field method. We demonstrate the existence of numerous exact duality relations linking quantities E{sup (N)}(m;Q) and E{sup (p)}(m';Q') for various forms of the potentials (independent of m and N) and for both nonrelativistic and semirelativistic kinematics. As the approximations computed with the auxiliary field method can be very close to the exact results, we show with several examples that these duality relations still hold, with sometimes a good accuracy, for the exact eigenenergies {epsilon}{sup (N)}(m;{l_brace}n{sub i}, l{sub i{r_brace}}).
NASA Astrophysics Data System (ADS)
Valdivia, Valeska; Hennebelle, Patrick
2014-11-01
Context. Ultraviolet radiation plays a crucial role in molecular clouds. Radiation and matter are tightly coupled and their interplay influences the physical and chemical properties of gas. In particular, modeling the radiation propagation requires calculating column densities, which can be numerically expensive in high-resolution multidimensional simulations. Aims: Developing fast methods for estimating column densities is mandatory if we are interested in the dynamical influence of the radiative transfer. In particular, we focus on the effect of the UV screening on the dynamics and on the statistical properties of molecular clouds. Methods: We have developed a tree-based method for a fast estimate of column densities, implemented in the adaptive mesh refinement code RAMSES. We performed numerical simulations using this method in order to analyze the influence of the screening on the clump formation. Results: We find that the accuracy for the extinction of the tree-based method is better than 10%, while the relative error for the column density can be much more. We describe the implementation of a method based on precalculating the geometrical terms that noticeably reduces the calculation time. To study the influence of the screening on the statistical properties of molecular clouds we present the probability distribution function of gas and the associated temperature per density bin and the mass spectra for different density thresholds. Conclusions: The tree-based method is fast and accurate enough to be used during numerical simulations since no communication is needed between CPUs when using a fully threaded tree. It is then suitable to parallel computing. We show that the screening for far UV radiation mainly affects the dense gas, thereby favoring low temperatures and affecting the fragmentation. We show that when we include the screening, more structures are formed with higher densities in comparison to the case that does not include this effect. We
Yang, Ching-Been; Chiang, Hsiu-Lu
2013-01-01
This study integrated thermally induced super-resolution into near-field photolithography and conducted simulation and analysis on line segment fabrication. This technique involves passing a laser beam through an aluminum-plated optical fiber probe onto a thin film of indium (approximately 10 nm thick). The indium film opens a melted aperture narrower than the width of the laser beam, creating a melted region and a crystalline region. The difference in penetration rate between the two regions leads to the generation of thermally induced super-resolution. This paper proposes a combination of Taguchi method with gray relational analysis, in which S/N ratios obtained using the Taguchi method are converted into gray relational grades to identify an optimal combination of parameters capable of meeting multiple quality objectives. This optimal combination includes a probe aperture of 100 nm (A1), exposure energy/μm of 0.002nJ/μm (B2), development time of 60 s (C3), and indium film with a thickness of 7 nm (D1). The optimal parameters were (A1B2C3D1) for the gray relational analysis and (A1B1C1D1) for the Taguchi method. Results showed a negative improvement of -14.3% in line width from 126.2 (Taguchi method) to 144.2 nm (gray relational analysis). Working depth, however, showed a significantly improvement of 140.4% from 5.7 (Taguchi method) to 13.7 nm (gray relational analysis). The proposed approach resolves the conflicts that commonly occur among factor levels in Taguchi analysis under the requirements of multiple quality requirements.
Kussmann, Jörg; Luenser, Arne; Beer, Matthias; Ochsenfeld, Christian
2015-03-07
An analytical method to calculate the molecular vibrational Hessian matrix at the self-consistent field level is presented. By analysis of the multipole expansions of the relevant derivatives of Coulomb-type two-electron integral contractions, we show that the effect of the perturbation on the electronic structure due to the displacement of nuclei decays at least as r{sup −2} instead of r{sup −1}. The perturbation is asymptotically local, and the computation of the Hessian matrix can, in principle, be performed with O(N) complexity. Our implementation exhibits linear scaling in all time-determining steps, with some rapid but quadratic-complexity steps remaining. Sample calculations illustrate linear or near-linear scaling in the construction of the complete nuclear Hessian matrix for sparse systems. For more demanding systems, scaling is still considerably sub-quadratic to quadratic, depending on the density of the underlying electronic structure.
Detection of gravity field source boundaries using deconvolution method
NASA Astrophysics Data System (ADS)
Zuo, Boxin; Hu, Xiangyun; Liang, Yin; Han, Qi
2014-12-01
Complications arise in the interpretation of gravity fields because of interference from systematic degradations, such as boundary blurring and distortion. The major sources of these degradations are the various systematic errors that inevitably occur during gravity field data acquisition, discretization and geophysical forward modelling. To address this problem, we evaluate deconvolution method that aim to detect the clear horizontal boundaries of anomalous sources by the suppression of systematic errors. A convolution-based multilayer projection model, based on the classical 3-D gravity field forward model, is innovatively derived to model the systematic error degradation. Our deconvolution algorithm is specifically designed based on this multilayer projection model, in which three types of systematic error are defined. The degradations of the different systematic errors are considered in the deconvolution algorithm. As the primary source of degradation, the convolution-based systematic error is the main object of the multilayer projection model. Both the random systematic error and the projection systematic error are shown to form an integral part of the multilayer projection model, and the mixed norm regularization method and the primal-dual optimization method are therefore employed to control these errors and stabilize the deconvolution solution. We herein analyse the parameter identification and convergence of the proposed algorithms, and synthetic and field data sets are both used to illustrate their effectiveness. Additional synthetic examples are specifically designed to analyse the effects of the projection systematic error, which is caused by the uncertainty associated with the estimation of the impulse response function.
A new method of field MRTD test
NASA Astrophysics Data System (ADS)
Chen, Zhibin; Song, Yan; Liu, Xianhong; Xiao, Wenjian
2014-09-01
MRTD is an important indicator to measure the imaging performance of infrared camera. In the traditional laboratory test, blackbody is used as simulated heat source which is not only expensive and bulky but also difficult to meet field testing requirements of online automatic infrared camera MRTD. To solve this problem, this paper introduces a new detection device for MRTD, which uses LED as a simulation heat source and branded plated zinc sulfide glass carved four-bar target as a simulation target. By using high temperature adaptability cassegrain collimation system, the target is simulated to be distance-infinite so that it can be observed by the human eyes to complete the subjective test, or collected to complete objective measurement by image processing. This method will use LED to replace blackbody. The color temperature of LED is calibrated by thermal imager, thereby, the relation curve between the LED temperature controlling current and the blackbody simulation temperature difference is established, accurately achieved the temperature control of the infrared target. Experimental results show that the accuracy of the device in field testing of thermal imager MRTD can be limited within 0.1K, which greatly reduces the cost to meet the project requirements with a wide application value.
Narrow field electromagnetic sensor system and method
McEwan, Thomas E.
1996-01-01
A narrow field electromagnetic sensor system and method of sensing a characteristic of an object provide the capability to realize a characteristic of an object such as density, thickness, or presence, for any desired coordinate position on the object. One application is imaging. The sensor can also be used as an obstruction detector or an electronic trip wire with a narrow field without the disadvantages of impaired performance when exposed to dirt, snow, rain, or sunlight. The sensor employs a transmitter for transmitting a sequence of electromagnetic signals in response to a transmit timing signal, a receiver for sampling only the initial direct RF path of the electromagnetic signal while excluding all other electromagnetic signals in response to a receive timing signal, and a signal processor for processing the sampled direct RF path electromagnetic signal and providing an indication of the characteristic of an object. Usually, the electromagnetic signal is a short RF burst and the obstruction must provide a substantially complete eclipse of the direct RF path. By employing time-of-flight techniques, a timing circuit controls the receiver to sample only the initial direct RF path of the electromagnetic signal while not sampling indirect path electromagnetic signals. The sensor system also incorporates circuitry for ultra-wideband spread spectrum operation that reduces interference to and from other RF services while allowing co-location of multiple electronic sensors without the need for frequency assignments.
Narrow field electromagnetic sensor system and method
McEwan, T.E.
1996-11-19
A narrow field electromagnetic sensor system and method of sensing a characteristic of an object provide the capability to realize a characteristic of an object such as density, thickness, or presence, for any desired coordinate position on the object. One application is imaging. The sensor can also be used as an obstruction detector or an electronic trip wire with a narrow field without the disadvantages of impaired performance when exposed to dirt, snow, rain, or sunlight. The sensor employs a transmitter for transmitting a sequence of electromagnetic signals in response to a transmit timing signal, a receiver for sampling only the initial direct RF path of the electromagnetic signal while excluding all other electromagnetic signals in response to a receive timing signal, and a signal processor for processing the sampled direct RF path electromagnetic signal and providing an indication of the characteristic of an object. Usually, the electromagnetic signal is a short RF burst and the obstruction must provide a substantially complete eclipse of the direct RF path. By employing time-of-flight techniques, a timing circuit controls the receiver to sample only the initial direct RF path of the electromagnetic signal while not sampling indirect path electromagnetic signals. The sensor system also incorporates circuitry for ultra-wideband spread spectrum operation that reduces interference to and from other RF services while allowing co-location of multiple electronic sensors without the need for frequency assignments. 12 figs.
Ogura, Toshihiko
2014-08-01
The high-resolution structural analysis of biological specimens by scanning electron microscopy (SEM) presents several advantages. Until now, wet bacterial specimens have been examined using atmospheric sample holders. However, images of unstained specimens in water using these holders exhibit very poor contrast and heavy radiation damage. Recently, we developed the frequency transmission electric-field (FTE) method, which facilitates the SEM observation of biological specimens in water without radiation damage. However, the signal detection system presents low sensitivity. Therefore, a high EB current is required to generate clear images, and thus reducing spatial resolution and inducing thermal damage to the samples. Here a high-sensitivity detection system is developed for the FTE method, which enhances the output signal amplitude by hundredfold. The detection signal was highly enhanced when voltage was applied to the metal layer on silicon nitride thin film. This enhancement reduced the EB current and improved the spatial resolution as well as the signal-to-noise ratio. The spatial resolution of a high-sensitive FTE system is 41nm, which is considerably higher than previous FTE system. New FTE system can easily be utilised to examine various unstained biological specimens in water, such as living bacteria and viruses. PMID:25058457
A field method for measurement of infiltration
Johnson, A.I.
1963-01-01
The determination of infiltration--the downward entry of water into a soil (or sediment)--is receiving increasing attention in hydrologic studies because of the need for more quantitative data on all phases of the hydrologic cycle. A measure of infiltration, the infiltration rate, is usually determined in the field by flooding basins or furrows, sprinkling, or measuring water entry from cylinders (infiltrometer rings). Rates determined by ponding in large areas are considered most reliable, but the high cost usually dictates that infiltrometer rings, preferably 2 feet in diameter or larger, be used. The hydrology of subsurface materials is critical in the study of infiltration. The zone controlling the rate of infiltration is usually the least permeable zone. Many other factors affect infiltration rate--the sediment (soil) structure, the condition of the sediment surface, the distribution of soil moisture or soil- moisture tension, the chemical and physical nature of the sediments, the head of applied water, the depth to ground water, the chemical quality and the turbidity of the applied water, the temperature of the water and the sediments, the percentage of entrapped air in the sediments, the atmospheric pressure, the length of time of application of water, the biological activity in the sediments, and the type of equipment or method used. It is concluded that specific values of the infiltration rate for a particular type of sediment are probably nonexistent and that measured rates are primarily for comparative use. A standard field-test method for determining infiltration rates by means of single- or double-ring infiltrometers is described and the construction, installation, and operation of the infiltrometers are discussed in detail.
NASA Astrophysics Data System (ADS)
Hayward, Nathan; Enkin, Randolph J.; Corriveau, Louise; Montreuil, Jean-François; Kerswill, John
2013-07-01
New techniques for the integration of gravity and aeromagnetic data through rock physical property relationships are tested for the rapid location of potential iron oxide-copper-gold (IOCG) exploration targets across the Great Bear magmatic zone (GBMZ). These techniques are based on the recognition of coincident or near-offset magnetic and gravity anomalies associated with IOCG deposits, resulting from their intense and combined iron-oxide and alkali alteration. In the GBMZ, the NICO (Au-Co-Bi-Cu) deposit is an atypical magnetite-group IOCG hosted within an intensely hydrothermally-altered metasedimentary sequence. Prospectivity maps for the NICO area are derived from the integration of high-resolution aeromagnetic and surface gravity data with physical property measurements of magnetic susceptibility and density. Method 1 combines the pseudo-gravity (derived from the aeromagnetic data) and Bouguer gravity data to determine the locations of superimposed high anomalies. Method 2 estimates the apparent susceptibility and density subsurface distribution based on vertical prism models of the magnetic and gravity data. The apparent susceptibility data are transformed to apparent density using physical property relationships. The two apparent density datasets are then combined to determine the location of coincident magnetic and gravity derived anomalies. The results of these methods are supported by, and compared with, similar prospectivity maps generated through weights of evidence techniques. At NICO, the prospectivity maps accurately locate the deposit and nearby occurrences. Despite the lower resolution of the regional gravity data, application of the techniques across the GBMZ is successful at locating mineralised IOCG systems including the magnetite-group systems at Grouard, Fab, DeVries and Cole Lake, the magnetite to hematite-group systems of the Port Radium-Echo Bay district, and has highlighted possible targets for future exploration.
Edison, John R.; Monson, Peter A.
2014-07-14
Recently we have developed a dynamic mean field theory (DMFT) for lattice gas models of fluids in porous materials [P. A. Monson, J. Chem. Phys. 128(8), 084701 (2008)]. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable states for fluids in pores and is especially useful for studying system exhibiting adsorption/desorption hysteresis. In this paper we discuss the extension of the theory to higher order by means of the path probability method (PPM) of Kikuchi and co-workers. We show that this leads to a treatment of the dynamics that is consistent with thermodynamics coming from the Bethe-Peierls or Quasi-Chemical approximation for the equilibrium or metastable equilibrium states of the lattice model. We compare the results from the PPM with those from DMFT and from dynamic Monte Carlo simulations. We find that the predictions from PPM are qualitatively similar to those from DMFT but give somewhat improved quantitative accuracy, in part due to the superior treatment of the underlying thermodynamics. This comes at the cost of greater computational expense associated with the larger number of equations that must be solved.
Field methods for measuring concentrated flow erosion
NASA Astrophysics Data System (ADS)
Castillo, C.; Pérez, R.; James, M. R.; Quinton, J. N.; Taguas, E. V.; Gómez, J. A.
2012-04-01
Many studies have stressed the importance of gully erosion in the overall soil loss and sediment yield of agricultural catchments, for instance in recent years (Vandaele and Poesen, 1995; De Santisteban et al., 2006; Wu el al, 2008). Several techniques have been used for determining gully erosion in field studies. The conventional techniques involved the use of different devices (i.e. ruler, pole, tape, micro-topographic profilers, total station) to calculate rill and gully volumes through the determination of cross sectional areas and length of reaches (Casalí et al, 1999; Hessel and van Asch, 2003). Optical devices (i.e. laser profilemeters) have also been designed for the purpose of rapid and detailed assessment of cross sectional areas in gully networks (Giménez et al., 2009). These conventional 2d methods provide a simple and un-expensive approach for erosion evaluation, but are time consuming to carry out if a good accuracy is required. On the other hand, remote sensing techniques are being increasingly applied to gully erosion investigation such as aerial photography used for big-scale, long-term, investigations (e.g. Martínez-Casasnovas et al., 2004; Ionita, 2006), airborne and terrestrial LiDAR datasets for gully volume evaluation (James et al., 2007; Evans and Lindsay, 2010) and recently, major advances in 3D photo-reconstruction techniques (Welty et al. 2010, James et al., 2011). Despite its interest, few studies simultaneously compare the accuracies of the range of conventional and remote sensing techniques used, or define the most suitable method for a particular scale, given and time and cost constraints. That was the reason behind the International Workshop Innovations in the evaluation and measurement of rill and gully erosion, held in Cordoba in May 2011 and from which derive part of the materials presented in this abstract. The main aim of this work was to compare the accuracy and time requirements of traditional (2D) and recently developed
New electric field methods in chemical relaxation spectrometry.
Persoons, A; Hellemans, L
1978-01-01
New stationary relaxation methods for the investigation of ionic and dipolar equilibria are presented. The methods are based on the measurement of non-linearities in conductance and permittivity under high electric field conditions. The chemical contributions to the nonlinear effects are discussed in their static as well as their dynamic behavior. A sampling of experimental results shows the potential and range of possible applications of the new techniques. It is shown that these methods will become useful in the study of nonlinear responses to perturbation, in view of the general applicability of the experimental principles involved. PMID:708817
Field testing method for photovaltaic modules
NASA Astrophysics Data System (ADS)
Ramos, Gerber N.
For remote areas, where solar photovoltaic modules are the only source of power, it is essential to perform preventive maintenance to insure that the PV system works properly; unfortunately, prices for PV testers range from 1,700 to 8,000. To address this issue, a portable inexpensive tester and analysis methodology have been developed. Assembling a simple tester, which costs $530 and weighs about 5 pounds, and using the Four-Parameters PV Model, we characterized the current-voltage (I-V) curve at environmental testing conditions; and then employing radiation, temperature, and age degradation sensitivity equations, we extrapolated the I-V curve to standard testing conditions. After applying the methodology to three kinds of silicon modules (mono-crystalline, multi-crystalline, and thin-film), we obtained maximum power points up to 97% of the manufacturer's specifications. Therefore, based on these results, it is reasonably accurate and affordable to verify the performance of solar modules in the field.
Potential theoretic methods for far field sound radiation calculations
NASA Technical Reports Server (NTRS)
Hariharan, S. I.; Stenger, Edward J.; Scott, J. R.
1995-01-01
In the area of computational acoustics, procedures which accurately predict the far-field sound radiation are much sought after. A systematic development of such procedures are found in a sequence of papers by Atassi. The method presented here is an alternate approach to predicting far field sound based on simple layer potential theoretic methods. The main advantages of this method are: it requires only a simple free space Green's function, it can accommodate arbitrary shapes of Kirchoff surfaces, and is readily extendable to three-dimensional problems. Moreover, the procedure presented here, though tested for unsteady lifting airfoil problems, can easily be adapted to other areas of interest, such as jet noise radiation problems. Results are presented for lifting airfoil problems and comparisons are made with the results reported by Atassi. Direct comparisons are also made for the flat plate case.
Knowledge-based flow field zoning
NASA Technical Reports Server (NTRS)
Andrews, Alison E.
1988-01-01
Automation flow field zoning in two dimensions is an important step towards easing the three-dimensional grid generation bottleneck in computational fluid dynamics. A knowledge based approach works well, but certain aspects of flow field zoning make the use of such an approach challenging. A knowledge based flow field zoner, called EZGrid, was implemented and tested on representative two-dimensional aerodynamic configurations. Results are shown which illustrate the way in which EZGrid incorporates the effects of physics, shape description, position, and user bias in a flow field zoning.
Zheng, Xiang; Yang, Chao; Cai, Xiao-Chuan; Keyes, David
2015-03-15
We present a numerical algorithm for simulating the spinodal decomposition described by the three dimensional Cahn–Hilliard–Cook (CHC) equation, which is a fourth-order stochastic partial differential equation with a noise term. The equation is discretized in space and time based on a fully implicit, cell-centered finite difference scheme, with an adaptive time-stepping strategy designed to accelerate the progress to equilibrium. At each time step, a parallel Newton–Krylov–Schwarz algorithm is used to solve the nonlinear system. We discuss various numerical and computational challenges associated with the method. The numerical scheme is validated by a comparison with an explicit scheme of high accuracy (and unreasonably high cost). We present steady state solutions of the CHC equation in two and three dimensions. The effect of the thermal fluctuation on the spinodal decomposition process is studied. We show that the existence of the thermal fluctuation accelerates the spinodal decomposition process and that the final steady morphology is sensitive to the stochastic noise. We also show the evolution of the energies and statistical moments. In terms of the parallel performance, it is found that the implicit domain decomposition approach scales well on supercomputers with a large number of processors.
NASA Astrophysics Data System (ADS)
Zheng, Xiang; Yang, Chao; Cai, Xiao-Chuan; Keyes, David
2015-03-01
We present a numerical algorithm for simulating the spinodal decomposition described by the three dimensional Cahn-Hilliard-Cook (CHC) equation, which is a fourth-order stochastic partial differential equation with a noise term. The equation is discretized in space and time based on a fully implicit, cell-centered finite difference scheme, with an adaptive time-stepping strategy designed to accelerate the progress to equilibrium. At each time step, a parallel Newton-Krylov-Schwarz algorithm is used to solve the nonlinear system. We discuss various numerical and computational challenges associated with the method. The numerical scheme is validated by a comparison with an explicit scheme of high accuracy (and unreasonably high cost). We present steady state solutions of the CHC equation in two and three dimensions. The effect of the thermal fluctuation on the spinodal decomposition process is studied. We show that the existence of the thermal fluctuation accelerates the spinodal decomposition process and that the final steady morphology is sensitive to the stochastic noise. We also show the evolution of the energies and statistical moments. In terms of the parallel performance, it is found that the implicit domain decomposition approach scales well on supercomputers with a large number of processors.
Abnormality degree detection method using negative potential field group detectors
NASA Astrophysics Data System (ADS)
Zhang, Hongli; Liu, Shulin; Li, Dong; Shi, Kunju; Wang, Bo; Cui, Jiqiang
2015-09-01
Online monitoring methods have been widely used in many major devices, however the normal and abnormal states of equipment are estimated mainly based on the monitoring results whether monitored parameters exceed the setting thresholds. Using these monitoring methods may cause serious false positive or false negative results. In order to precisely monitor the state of equipment, the problem of abnormality degree detection without fault sample is studied with a new detection method called negative potential field group detectors(NPFG-detectors). This method achieves the quantitative expression of abnormality degree and provides the better detection results compared with other methods. In the process of Iris data set simulation, the new algorithm obtains the successful results in abnormal detection. The detection rates for 3 types of Iris data set respectively reach 100%, 91.6%, and 95.24% with 50% training samples. The problem of Bearing abnormality degree detection via an abnormality degree curve is successfully solved.
Gravitational collapse of scalar fields via spectral methods
Oliveira, H. P. de; Rodrigues, E. L.; Skea, J. E. F.
2010-11-15
In this paper we present a new numerical code based on the Galerkin method to integrate the field equations for the spherical collapse of massive and massless scalar fields. By using a spectral decomposition in terms of the radial coordinate, the field equations were reduced to a finite set of ordinary differential equations in the space of modes associated with the Galerkin expansion of the scalar field, together with algebraic sets of equations connecting modes associated with the metric functions. The set of ordinary differential equations with respect to the null coordinate is then integrated using an eighth-order Runge-Kutta method. The numerical tests have confirmed the high accuracy and fast convergence of the code. As an application we have evaluated the whole spectrum of black hole masses which ranges from infinitesimal to large values obtained after varying the amplitude of the initial scalar field distribution. We have found strong numerical evidence that this spectrum is described by a nonextensive distribution law.
Magnetic field transfer device and method
Wipf, Stefan L.
1990-01-01
A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180.degree. from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180.degree. from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils.
Magnetic field transfer device and method
Wipf, S.L.
1990-02-13
A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180[degree] from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180[degree] from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils. 16 figs.
Process system and method for fabricating submicron field emission cathodes
Jankowski, Alan F.; Hayes, Jeffrey P.
1998-01-01
A process method and system for making field emission cathodes exists. The deposition source divergence is controlled to produce field emission cathodes with height-to-base aspect ratios that are uniform over large substrate surface areas while using very short source-to-substrate distances. The rate of hole closure is controlled from the cone source. The substrate surface is coated in well defined increments. The deposition source is apertured to coat pixel areas on the substrate. The entire substrate is coated using a manipulator to incrementally move the whole substrate surface past the deposition source. Either collimated sputtering or evaporative deposition sources can be used. The position of the aperture and its size and shape are used to control the field emission cathode size and shape.
Junction-based field emission structure for field emission display
Dinh, Long N.; Balooch, Mehdi; McLean, II, William; Schildbach, Marcus A.
2002-01-01
A junction-based field emission display, wherein the junctions are formed by depositing a semiconducting or dielectric, low work function, negative electron affinity (NEA) silicon-based compound film (SBCF) onto a metal or n-type semiconductor substrate. The SBCF can be doped to become a p-type semiconductor. A small forward bias voltage is applied across the junction so that electron transport is from the substrate into the SBCF region. Upon entering into this NEA region, many electrons are released into the vacuum level above the SBCF surface and accelerated toward a positively biased phosphor screen anode, hence lighting up the phosphor screen for display. To turn off, simply switch off the applied potential across the SBCF/substrate. May be used for field emission flat panel displays.
Thomer, Andrea; Vaidya, Gaurav; Guralnick, Robert; Bloom, David; Russell, Laura
2012-01-01
Part diary, part scientific record, biological field notebooks often contain details necessary to understanding the location and environmental conditions existent during collecting events. Despite their clear value for (and recent use in) global change studies, the text-mining outputs from field notebooks have been idiosyncratic to specific research projects, and impossible to discover or re-use. Best practices and workflows for digitization, transcription, extraction, and integration with other sources are nascent or non-existent. In this paper, we demonstrate a workflow to generate structured outputs while also maintaining links to the original texts. The first step in this workflow was to place already digitized and transcribed field notebooks from the University of Colorado Museum of Natural History founder, Junius Henderson, on Wikisource, an open text transcription platform. Next, we created Wikisource templates to document places, dates, and taxa to facilitate annotation and wiki-linking. We then requested help from the public, through social media tools, to take advantage of volunteer efforts and energy. After three notebooks were fully annotated, content was converted into XML and annotations were extracted and cross-walked into Darwin Core compliant record sets. Finally, these recordsets were vetted, to provide valid taxon names, via a process we call "taxonomic referencing." The result is identification and mobilization of 1,068 observations from three of Henderson's thirteen notebooks and a publishable Darwin Core record set for use in other analyses. Although challenges remain, this work demonstrates a feasible approach to unlock observations from field notebooks that enhances their discovery and interoperability without losing the narrative context from which those observations are drawn."Compose your notes as if you were writing a letter to someone a century in the future."Perrine and Patton (2011). PMID:22859891
Thomer, Andrea; Vaidya, Gaurav; Guralnick, Robert; Bloom, David; Russell, Laura
2012-01-01
Abstract Part diary, part scientific record, biological field notebooks often contain details necessary to understanding the location and environmental conditions existent during collecting events. Despite their clear value for (and recent use in) global change studies, the text-mining outputs from field notebooks have been idiosyncratic to specific research projects, and impossible to discover or re-use. Best practices and workflows for digitization, transcription, extraction, and integration with other sources are nascent or non-existent. In this paper, we demonstrate a workflow to generate structured outputs while also maintaining links to the original texts. The first step in this workflow was to place already digitized and transcribed field notebooks from the University of Colorado Museum of Natural History founder, Junius Henderson, on Wikisource, an open text transcription platform. Next, we created Wikisource templates to document places, dates, and taxa to facilitate annotation and wiki-linking. We then requested help from the public, through social media tools, to take advantage of volunteer efforts and energy. After three notebooks were fully annotated, content was converted into XML and annotations were extracted and cross-walked into Darwin Core compliant record sets. Finally, these recordsets were vetted, to provide valid taxon names, via a process we call “taxonomic referencing.” The result is identification and mobilization of 1,068 observations from three of Henderson’s thirteen notebooks and a publishable Darwin Core record set for use in other analyses. Although challenges remain, this work demonstrates a feasible approach to unlock observations from field notebooks that enhances their discovery and interoperability without losing the narrative context from which those observations are drawn. “Compose your notes as if you were writing a letter to someone a century in the future.” Perrine and Patton (2011) PMID:22859891
Dispersion-Corrected Mean-Field Electronic Structure Methods.
Grimme, Stefan; Hansen, Andreas; Brandenburg, Jan Gerit; Bannwarth, Christoph
2016-05-11
Mean-field electronic structure methods like Hartree-Fock, semilocal density functional approximations, or semiempirical molecular orbital (MO) theories do not account for long-range electron correlation (London dispersion interaction). Inclusion of these effects is mandatory for realistic calculations on large or condensed chemical systems and for various intramolecular phenomena (thermochemistry). This Review describes the recent developments (including some historical aspects) of dispersion corrections with an emphasis on methods that can be employed routinely with reasonable accuracy in large-scale applications. The most prominent correction schemes are classified into three groups: (i) nonlocal, density-based functionals, (ii) semiclassical C6-based, and (iii) one-electron effective potentials. The properties as well as pros and cons of these methods are critically discussed, and typical examples and benchmarks on molecular complexes and crystals are provided. Although there are some areas for further improvement (robustness, many-body and short-range effects), the situation regarding the overall accuracy is clear. Various approaches yield long-range dispersion energies with a typical relative error of 5%. For many chemical problems, this accuracy is higher compared to that of the underlying mean-field method (i.e., a typical semilocal (hybrid) functional like B3LYP). PMID:27077966
Forest health monitoring: Field methods guide
Tallent-Halsell, N.G.
1994-10-01
This guide is intended to instruct Forest Health Monitors when collecting data on forest health indicators; site condition, growth and regeneration, crown condition, tree damage and mortality assessment, photosynthetically active radiation, vegetation structure, ozone bioindicator species, lichen community structure and field logistics. This guide contains information on measuring, observing and recording data related to the above listed forest health indicators. Pertinent quality assurance information is also included.
Stream temperature investigations: field and analytic methods
Bartholow, J.M.
1989-01-01
Alternative public domain stream and reservoir temperature models are contrasted with SNTEMP. A distinction is made between steady-flow and dynamic-flow models and their respective capabilities. Regression models are offered as an alternative approach for some situations, with appropriate mathematical formulas suggested. Appendices provide information on State and Federal agencies that are good data sources, vendors for field instrumentation, and small computer programs useful in data reduction.
NASA Astrophysics Data System (ADS)
Chirouze, J.; Boulet, G.; Jarlan, L.; Fieuzal, R.; Rodriguez, J. C.; Ezzahar, J.; Er-Raki, S.; Bigeard, G.; Merlin, O.; Garatuza-Payan, J.; Watts, C.; Chehbouni, G.
2013-01-01
Remotely sensed surface temperature can provide a good proxy for water stress level and is therefore particularly useful to estimate spatially distributed evapotranspiration. Instantaneous stress levels or instantaneous latent heat flux are deduced from the surface energy balance equation constrained by this equilibrium temperature. Pixel average surface temperature depends on two main factors: stress and vegetation fraction cover. Methods estimating stress vary according to the way they treat each factor. Two families of methods can be defined: the contextual methods, where stress levels are scaled on a given image between hot/dry and cool/wet pixels for a particular vegetation cover, and single-pixel methods which evaluate latent heat as the residual of the surface energy balance for one pixel independently from the others. Four models, two contextual (S-SEBI and a triangle method, inspired by Moran et al., 1994) and two single-pixel (TSEB, SEBS) are applied at seasonal scale over a four by four km irrigated agricultural area in semi-arid northern Mexico. Their performances, both at local and spatial standpoints, are compared relatively to energy balance data acquired at seven locations within the area, as well as a more complex soil-vegetation-atmosphere transfer model forced with true irrigation and rainfall data. Stress levels are not always well retrieved by most models, but S-SEBI as well as TSEB, although slightly biased, show good performances. Drop in model performances is observed when vegetation is senescent, mostly due to a poor partitioning both between turbulent fluxes and between the soil/plant components of the latent heat flux and the available energy. As expected, contextual methods perform well when extreme hydric and vegetation conditions are encountered in the same image (therefore, esp. in spring and early summer) while they tend to exaggerate the spread in water status in more homogeneous conditions (esp. in winter).
This paper summarizes and discusses recent available U.S. and European information on
ammonia (NH3) emissions from swine farms and assesses the applicability for general use
in the United States. The emission rates for the swine barns calculated by various methods show
g...
Dispersion Method Using Focused Ultrasonic Field
NASA Astrophysics Data System (ADS)
Kim, Jungsoon; Kim, Moojoon; Ha, Kanglyel; Chu, Minchul
2010-07-01
The dispersion of powders into liquids has become one of the most important techniques in high-tech industries and it is a common process in the formulation of various products, such as paint, ink, shampoo, beverages, and polishing media. In this study, an ultrasonic system with a cylindrical transducer is newly introduced for pure nanoparticle dispersion. The acoustics pressure field and the characteristics of the shock pulse caused by cavitation are investigated. The frequency spectrum of the pulse from the collapse of air bubbles in the cavitation is analyzed theoretically. It was confirmed that a TiO2 water suspension can be dispersed effectively using the suggested system.
NASA Astrophysics Data System (ADS)
Chirouze, J.; Boulet, G.; Jarlan, L.; Fieuzal, R.; Rodriguez, J. C.; Ezzahar, J.; Er-Raki, S.; Bigeard, G.; Merlin, O.; Garatuza-Payan, J.; Watts, C.; Chehbouni, G.
2014-03-01
Instantaneous evapotranspiration rates and surface water stress levels can be deduced from remotely sensed surface temperature data through the surface energy budget. Two families of methods can be defined: the contextual methods, where stress levels are scaled on a given image between hot/dry and cool/wet pixels for a particular vegetation cover, and single-pixel methods, which evaluate latent heat as the residual of the surface energy balance for one pixel independently from the others. Four models, two contextual (S-SEBI and a modified triangle method, named VIT) and two single-pixel (TSEB, SEBS) are applied over one growing season (December-May) for a 4 km × 4 km irrigated agricultural area in the semi-arid northern Mexico. Their performance, both at local and spatial standpoints, are compared relatively to energy balance data acquired at seven locations within the area, as well as an uncalibrated soil-vegetation-atmosphere transfer (SVAT) model forced with local in situ data including observed irrigation and rainfall amounts. Stress levels are not always well retrieved by most models, but S-SEBI as well as TSEB, although slightly biased, show good performance. The drop in model performance is observed for all models when vegetation is senescent, mostly due to a poor partitioning both between turbulent fluxes and between the soil/plant components of the latent heat flux and the available energy. As expected, contextual methods perform well when contrasted soil moisture and vegetation conditions are encountered in the same image (therefore, especially in spring and early summer) while they tend to exaggerate the spread in water status in more homogeneous conditions (especially in winter). Surface energy balance models run with available remotely sensed products prove to be nearly as accurate as the uncalibrated SVAT model forced with in situ data.
Determination of traces of cobalt in soils: A field method
Almond, H.
1953-01-01
The growing use of geochemical prospecting methods in the search for ore deposits has led to the development of a field method for the determination of cobalt in soils. The determination is based on the fact that cobalt reacts with 2-nitroso-1-naphthol to yield a pink compound that is soluble in carbon tetrachloride. The carbon tetrachloride extract is shaken with dilute cyanide to complex interfering elements and to remove excess reagent. The cobalt content is estimated by comparing the pink color in the carbon tetrachloride with a standard series prepared from standard solutions. The cobalt 2-nitroso-1-naphtholate system in carbon tetrachloride follows Beer's law. As little as 1 p.p.m. can be determined in a 0.1-gram sample. The method is simple and fast and requires only simple equipment. More than 40 samples can be analyzed per man-day with an accuracy within 30% or better.
Yoshikawa, Takeshi; Nakai, Hiromi
2015-01-30
Graphical processing units (GPUs) are emerging in computational chemistry to include Hartree-Fock (HF) methods and electron-correlation theories. However, ab initio calculations of large molecules face technical difficulties such as slow memory access between central processing unit and GPU and other shortfalls of GPU memory. The divide-and-conquer (DC) method, which is a linear-scaling scheme that divides a total system into several fragments, could avoid these bottlenecks by separately solving local equations in individual fragments. In addition, the resolution-of-the-identity (RI) approximation enables an effective reduction in computational cost with respect to the GPU memory. The present study implemented the DC-RI-HF code on GPUs using math libraries, which guarantee compatibility with future development of the GPU architecture. Numerical applications confirmed that the present code using GPUs significantly accelerated the HF calculations while maintaining accuracy.
Advanced Fuzzy Potential Field Method for Mobile Robot Obstacle Avoidance
Park, Jong-Wook; Kwak, Hwan-Joo; Kang, Young-Chang; Kim, Dong W.
2016-01-01
An advanced fuzzy potential field method for mobile robot obstacle avoidance is proposed. The potential field method primarily deals with the repulsive forces surrounding obstacles, while fuzzy control logic focuses on fuzzy rules that handle linguistic variables and describe the knowledge of experts. The design of a fuzzy controller—advanced fuzzy potential field method (AFPFM)—that models and enhances the conventional potential field method is proposed and discussed. This study also examines the rule-explosion problem of conventional fuzzy logic and assesses the performance of our proposed AFPFM through simulations carried out using a mobile robot. PMID:27123001
Advanced Fuzzy Potential Field Method for Mobile Robot Obstacle Avoidance.
Park, Jong-Wook; Kwak, Hwan-Joo; Kang, Young-Chang; Kim, Dong W
2016-01-01
An advanced fuzzy potential field method for mobile robot obstacle avoidance is proposed. The potential field method primarily deals with the repulsive forces surrounding obstacles, while fuzzy control logic focuses on fuzzy rules that handle linguistic variables and describe the knowledge of experts. The design of a fuzzy controller--advanced fuzzy potential field method (AFPFM)--that models and enhances the conventional potential field method is proposed and discussed. This study also examines the rule-explosion problem of conventional fuzzy logic and assesses the performance of our proposed AFPFM through simulations carried out using a mobile robot. PMID:27123001
Path planning in uncertain flow fields using ensemble method
NASA Astrophysics Data System (ADS)
Wang, Tong; Le Maître, Olivier P.; Hoteit, Ibrahim; Knio, Omar M.
2016-08-01
An ensemble-based approach is developed to conduct optimal path planning in unsteady ocean currents under uncertainty. We focus our attention on two-dimensional steady and unsteady uncertain flows, and adopt a sampling methodology that is well suited to operational forecasts, where an ensemble of deterministic predictions is used to model and quantify uncertainty. In an operational setting, much about dynamics, topography, and forcing of the ocean environment is uncertain. To address this uncertainty, the flow field is parametrized using a finite number of independent canonical random variables with known densities, and the ensemble is generated by sampling these variables. For each of the resulting realizations of the uncertain current field, we predict the path that minimizes the travel time by solving a boundary value problem (BVP), based on the Pontryagin maximum principle. A family of backward-in-time trajectories starting at the end position is used to generate suitable initial values for the BVP solver. This allows us to examine and analyze the performance of the sampling strategy and to develop insight into extensions dealing with general circulation ocean models. In particular, the ensemble method enables us to perform a statistical analysis of travel times and consequently develop a path planning approach that accounts for these statistics. The proposed methodology is tested for a number of scenarios. We first validate our algorithms by reproducing simple canonical solutions, and then demonstrate our approach in more complex flow fields, including idealized, steady and unsteady double-gyre flows.
Path planning in uncertain flow fields using ensemble method
NASA Astrophysics Data System (ADS)
Wang, Tong; Le Maître, Olivier P.; Hoteit, Ibrahim; Knio, Omar M.
2016-10-01
An ensemble-based approach is developed to conduct optimal path planning in unsteady ocean currents under uncertainty. We focus our attention on two-dimensional steady and unsteady uncertain flows, and adopt a sampling methodology that is well suited to operational forecasts, where an ensemble of deterministic predictions is used to model and quantify uncertainty. In an operational setting, much about dynamics, topography, and forcing of the ocean environment is uncertain. To address this uncertainty, the flow field is parametrized using a finite number of independent canonical random variables with known densities, and the ensemble is generated by sampling these variables. For each of the resulting realizations of the uncertain current field, we predict the path that minimizes the travel time by solving a boundary value problem (BVP), based on the Pontryagin maximum principle. A family of backward-in-time trajectories starting at the end position is used to generate suitable initial values for the BVP solver. This allows us to examine and analyze the performance of the sampling strategy and to develop insight into extensions dealing with general circulation ocean models. In particular, the ensemble method enables us to perform a statistical analysis of travel times and consequently develop a path planning approach that accounts for these statistics. The proposed methodology is tested for a number of scenarios. We first validate our algorithms by reproducing simple canonical solutions, and then demonstrate our approach in more complex flow fields, including idealized, steady and unsteady double-gyre flows.
Symstad, Amy J.; Wienk, Cody L.; Thorstenson, Andy
2006-01-01
The Northern Great Plains Inventory & Monitoring (I&M) Network (Network) of the National Park Service (NPS) consists of 13 NPS units in North Dakota, South Dakota, Nebraska, and eastern Wyoming. The Network is in the planning phase of a long-term program to monitor the health of park ecosystems. Plant community composition is one of the 'Vital Signs,' or indicators, that will be monitored as part of this program for three main reasons. First, plant community composition is information-rich; a single sampling protocol can provide information on the diversity of native and non-native species, the abundance of individual dominant species, and the abundance of groups of plants. Second, plant community composition is of specific management concern. The abundance and diversity of exotic plants, both absolute and relative to native species, is one of the greatest management concerns in almost all Network parks (Symstad 2004). Finally, plant community composition reflects the effects of a variety of current or anticipated stressors on ecosystem health in the Network parks including invasive exotic plants, large ungulate grazing, lack of fire in a fire-adapted system, chemical exotic plant control, nitrogen deposition, increased atmospheric carbon dioxide concentrations, and climate change. Before the Network begins its Vital Signs monitoring, a detailed plan describing specific protocols used for each of the Vital Signs must go through rigorous development and review. The pilot study on which we report here is one of the components of this protocol development. The goal of the work we report on here was to determine a specific method to use for monitoring plant community composition of the herb layer (< 2 m tall).
On a spectral method for forward gravity field modelling
NASA Astrophysics Data System (ADS)
Root, B. C.; Novák, P.; Dirkx, D.; Kaban, M.; van der Wal, W.; Vermeersen, L. L. A.
2016-07-01
This article reviews a spectral forward gravity field modelling method that was initially designed for topographic/isostatic mass reduction of gravity data. The method transforms 3D spherical density models into gravitational potential fields using a spherical harmonic representation. The binomial series approximation in the approach, which is crucial for its computational efficiency, is examined and an error analysis is performed. It is shown that, this method cannot be used for density layers in crustal and upper mantle regions, because it results in large errors in the modelled potential field. Here, a correction is proposed to mitigate this erroneous behaviour. The improved method is benchmarked with a tesseroid gravity field modelling method and is shown to be accurate within ±4 mGal for a layer representing the Moho density interface, which is below other errors in gravity field studies. After the proposed adjustment the method can be used for the global gravity modelling of the complete Earth's density structure.
A squash preparation method for root meristem field studies.
Dubrovsky, J G; Contreras-Burciaga, L
1998-03-01
We present a field method for squash preparation of root apical meristem that does not require dry ice for cell adhesion to a slide. The method is based on the use of a weak gelatin solution as a stabilizing agent to prevent cell loss. Alcian blue 8GX was used as a counterstain for better recognition of cell shapes. Root meristems of Sonoran Desert succulents were used to illustrate the method. Fixed root tips were stained by Feulgen and squashes were prepared in a 1:2 mixture of solution A (45% acetic acid) and solution B (3:1 mixture of 0.5% gelatin in water:0.02% of alcian blue 8GX in 45% acetic acid). After squashing, the material was lightly dried for 5-6 min, then dehydrated and mounted in Canada balsam. Our method permits observation of chromosomes, recognition of meristematic and nonmeristematic cells, and estimation of mitotic indices and thus recognition of growing, dormant, and dead roots. The method can be used for estimation of cell division cycle time by colchicine and other methods where squash preparation is required.
NASA Astrophysics Data System (ADS)
Hamada, Shoji; Yamamoto, Osamu; Kobayashi, Tetsuo
This paper presents a generalized equivalent multipole-moment method for calculating three-dimensional Laplacian fields in multi-spherical system. The Greengard & Rokhlin's M2M, M2L, and L2L formulae enable the multipole-moment method to calculate the fields in general arrangement of multi-spheres, which involve exclusive and multi-layered spherical arrangement. We applied this method to electric field calculation in biological structures induced by ELF magnetic fields. The induced electric fields in a three eccentric and exclusive spheres system, which models human head with two eyeballs, are calculated under the application of homogeneous and magnetic-dipole fields. The validity of this method is successfully confirmed by comparing the calculated fields with those by the fast-multipole surface-charge-simulation method.
On conductance-based neural field models
Pinotsis, Dimitris A.; Leite, Marco; Friston, Karl J.
2013-01-01
This technical note introduces a conductance-based neural field model that combines biologically realistic synaptic dynamics—based on transmembrane currents—with neural field equations, describing the propagation of spikes over the cortical surface. This model allows for fairly realistic inter-and intra-laminar intrinsic connections that underlie spatiotemporal neuronal dynamics. We focus on the response functions of expected neuronal states (such as depolarization) that generate observed electrophysiological signals (like LFP recordings and EEG). These response functions characterize the model's transfer functions and implicit spectral responses to (uncorrelated) input. Our main finding is that both the evoked responses (impulse response functions) and induced responses (transfer functions) show qualitative differences depending upon whether one uses a neural mass or field model. Furthermore, there are differences between the equivalent convolution and conductance models. Overall, all models reproduce a characteristic increase in frequency, when inhibition was increased by increasing the rate constants of inhibitory populations. However, convolution and conductance-based models showed qualitatively different changes in power, with convolution models showing decreases with increasing inhibition, while conductance models show the opposite effect. These differences suggest that conductance based field models may be important in empirical studies of cortical gain control or pharmacological manipulations. PMID:24273508
NASA Astrophysics Data System (ADS)
Qi, Zhipeng; Li, Xiu; Lu, Xushan; Zhang, Yingying; Yao, Weihua
2015-04-01
We introduce a new and potentially useful method for wave field inverse transformation and its application in transient electromagnetic method (TEM) 3D interpretation. The diffusive EM field is known to have a unique integral representation in terms of a fictitious wave field that satisfies a wave equation. The continuous imaging of TEM can be accomplished using the imaging methods in seismic interpretation after the diffusion equation is transformed into a fictitious wave equation. The interpretation method based on the imaging of a fictitious wave field could be used as a fast 3D inversion method. Moreover, the fictitious wave field possesses some wave field features making it possible for the application of a wave field interpretation method in TEM to improve the prospecting resolution. Wave field transformation is a key issue in the migration imaging of a fictitious wave field. The equation in the wave field transformation belongs to the first class Fredholm integration equation, which is a typical ill-posed equation. Additionally, TEM has a large dynamic time range, which also facilitates the weakness of this ill-posed problem. The wave field transformation is implemented by using pre-conditioned regularized conjugate gradient method. The continuous imaging of a fictitious wave field is implemented by using Kirchhoff integration. A synthetic aperture and deconvolution algorithm is also introduced to improve the interpretation resolution. We interpreted field data by the method proposed in this paper, and obtained a satisfying interpretation result.
Classical fields method for a relativistic interacting Bose gas
Witkowska, Emilia; Zin, Pawel; Gajda, Mariusz
2009-01-15
We formulate a classical fields method for the description of relativistic interacting bosonic particles at nonzero temperatures. The method relies on the assumption that at low temperatures the Bose field can be described by a c-number function. We discuss a very important role of the cutoff momentum which divides the field into a dominant classical part and a small quantum correction. We illustrate the method by studying the thermodynamics of a relativistic Bose field which is governed by the Klein-Gordon equation with a {lambda}{psi}{sup 4} term responsible for the interactions.
Bootstrapping conformal field theories with the extremal functional method.
El-Showk, Sheer; Paulos, Miguel F
2013-12-13
The existence of a positive linear functional acting on the space of (differences between) conformal blocks has been shown to rule out regions in the parameter space of conformal field theories (CFTs). We argue that at the boundary of the allowed region the extremal functional contains, in principle, enough information to determine the dimensions and operator product expansion (OPE) coefficients of an infinite number of operators appearing in the correlator under analysis. Based on this idea we develop the extremal functional method (EFM), a numerical procedure for deriving the spectrum and OPE coefficients of CFTs lying on the boundary (of solution space). We test the EFM by using it to rederive the low lying spectrum and OPE coefficients of the two-dimensional Ising model based solely on the dimension of a single scalar quasiprimary--no Virasoro algebra required. Our work serves as a benchmark for applications to more interesting, less known CFTs in the near future. PMID:24483643
Bootstrapping conformal field theories with the extremal functional method.
El-Showk, Sheer; Paulos, Miguel F
2013-12-13
The existence of a positive linear functional acting on the space of (differences between) conformal blocks has been shown to rule out regions in the parameter space of conformal field theories (CFTs). We argue that at the boundary of the allowed region the extremal functional contains, in principle, enough information to determine the dimensions and operator product expansion (OPE) coefficients of an infinite number of operators appearing in the correlator under analysis. Based on this idea we develop the extremal functional method (EFM), a numerical procedure for deriving the spectrum and OPE coefficients of CFTs lying on the boundary (of solution space). We test the EFM by using it to rederive the low lying spectrum and OPE coefficients of the two-dimensional Ising model based solely on the dimension of a single scalar quasiprimary--no Virasoro algebra required. Our work serves as a benchmark for applications to more interesting, less known CFTs in the near future.
Some equivalences between the auxiliary field method and envelope theory
Buisseret, Fabien; Semay, Claude; Silvestre-Brac, Bernard
2009-03-15
The auxiliary field method has been recently proposed as an efficient technique to compute analytical approximate solutions of eigenequations in quantum mechanics. We show that the auxiliary field method is completely equivalent to the envelope theory, which is another well-known procedure to analytically solve eigenequations, although relying on different principles a priori. This equivalence leads to a deeper understanding of both frameworks.
Ocean Wave Simulation Based on Wind Field.
Li, Zhongyi; Wang, Hao
2016-01-01
Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates. PMID:26808718
Ocean Wave Simulation Based on Wind Field.
Li, Zhongyi; Wang, Hao
2016-01-01
Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates.
Ocean Wave Simulation Based on Wind Field
2016-01-01
Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates. PMID:26808718
NASA Astrophysics Data System (ADS)
Su, Xiaoru; Shu, Longcang; Chen, Xunhong; Lu, Chengpeng; Wen, Zhonghui
2016-08-01
Interactions between surface waters and groundwater are of great significance for evaluating water resources and protecting ecosystem health. Heat as a tracer method is widely used in determination of the interactive exchange with high precision, low cost and great convenience. The flow in a river-bank cross-section occurs in vertical and lateral directions. In order to depict the flow path and its spatial distribution in bank areas, a genetic algorithm (GA) two-dimensional (2-D) heat-transport nested-loop method for variably saturated sediments, GA-VS2DH, was developed based on Microsoft Visual Basic 6.0. VS2DH was applied to model a 2-D bank-water flow field and GA was used to calibrate the model automatically by minimizing the difference between observed and simulated temperatures in bank areas. A hypothetical model was developed to assess the reliability of GA-VS2DH in inverse modeling in a river-bank system. Some benchmark tests were conducted to recognize the capability of GA-VS2DH. The results indicated that the simulated seepage velocity and parameters associated with GA-VS2DH were acceptable and reliable. Then GA-VS2DH was applied to two field sites in China with different sedimentary materials, to verify the reliability of the method. GA-VS2DH could be applied in interpreting the cross-sectional 2-D water flow field. The estimates of horizontal hydraulic conductivity at the Dawen River and Qinhuai River sites are 1.317 and 0.015 m/day, which correspond to sand and clay sediment in the two sites, respectively.
Evaluation of field methods for vertical high resolution aquifer characterization
NASA Astrophysics Data System (ADS)
Vienken, T.; Tinter, M.; Rogiers, B.; Leven, C.; Dietrich, P.
2012-12-01
The delineation and characterization of subsurface (hydro)-stratigraphic structures is one of the challenging tasks of hydrogeological site investigations. The knowledge about the spatial distribution of soil specific properties and hydraulic conductivity (K) is the prerequisite for understanding flow and fluid transport processes. This is especially true for heterogeneous unconsolidated sedimentary deposits with a complex sedimentary architecture. One commonly used approach to investigate and characterize sediment heterogeneity is soil sampling and lab analyses, e.g. grain size distribution. Tests conducted on 108 samples show that calculation of K based on grain size distribution is not suitable for high resolution aquifer characterization of highly heterogeneous sediments due to sampling effects and large differences of calculated K values between applied formulas (Vienken & Dietrich 2011). Therefore, extensive tests were conducted at two test sites under different geological conditions to evaluate the performance of innovative Direct Push (DP) based approaches for the vertical high resolution determination of K. Different DP based sensor probes for the in-situ subsurface characterization based on electrical, hydraulic, and textural soil properties were used to obtain high resolution vertical profiles. The applied DP based tools proved to be a suitable and efficient alternative to traditional approaches. Despite resolution differences, all of the applied methods captured the main aquifer structure. Correlation of the DP based K estimates and proxies with DP based slug tests show that it is possible to describe the aquifer hydraulic structure on less than a meter scale by combining DP slug test data and continuous DP measurements. Even though correlations are site specific and appropriate DP tools must be chosen, DP is reliable and efficient alternative for characterizing even strongly heterogeneous sites with complex structured sedimentary aquifers (Vienken et
Combining Monte Carlo and mean-field-like methods for inference in hidden Markov random fields.
Forbes, Florence; Fort, Gersende
2007-03-01
Issues involving missing data are typical settings where exact inference is not tractable as soon as nontrivial interactions occur between the missing variables. Approximations are required, and most of them are based either on simulation methods or on deterministic variational methods. While variational methods provide fast and reasonable approximate estimates in many scenarios, simulation methods offer more consideration of important theoretical issues such as accuracy of the approximation and convergence of the algorithms but at a much higher computational cost. In this work, we propose a new class of algorithms that combine the main features and advantages of both simulation and deterministic methods and consider applications to inference in hidden Markov random fields (HMRFs). These algorithms can be viewed as stochastic perturbations of variational expectation maximization (VEM) algorithms, which are not tractable for HMRF. We focus more specifically on one of these perturbations and we prove their (almost sure) convergence to the same limit set as the limit set of VEM. In addition, experiments on synthetic and real-world images show that the algorithm performance is very close and sometimes better than that of other existing simulation-based and variational EM-like algorithms.
Classification method based on KCCA
NASA Astrophysics Data System (ADS)
Wang, Zhanqing; Zhang, Guilin; Zhao, Guangzhou
2007-11-01
Nonlinear CCA extends the linear CCA in that it operates in the kernel space and thus implies the nonlinear combinations in the original space. This paper presents a classification method based on the kernel canonical correlation analysis (KCCA). We introduce the probabilistic label vectors (PLV) for a give pattern which extend the conventional concept of class label, and investigate the correlation between feature variables and PLV variables. A PLV predictor is presented based on KCCA, and then classification is performed on the predicted PLV. We formulate a frame for classification by integrating class information through PLV. Experimental results on Iris data set classification and facial expression recognition show the efficiencies of the proposed method.
Classical-field methods for atom-molecule systems
NASA Astrophysics Data System (ADS)
Sahlberg, Catarina E.; Gardiner, C. W.
2013-02-01
We extend classical-field methods [Blakie , Adv. Phys.ADPHAH0001-873210.1080/00018730802564254 57, 363 (2008)] to provide a description of atom-molecule systems. We use a model of Bose-Einstein condensation of atoms close to a Feshbach resonance, in which the tunable scattering length of the atoms is described using a system of coupled atom and molecule fields [Holland , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.86.1915 86, 1915 (2001)]. We formulate the basic theoretical methods for a coupled atom-molecule system, including the determination of the phenomenological parameters in our system, the Thomas-Fermi description of Bose-Einstein condensate, the Bogoliubov-de Gennes equations, and the Bogoliubov excitation spectrum for a homogenous condensed system. We apply this formalism to the special case of Bragg scattering from a uniform condensate and find that for moderate and large scattering lengths, there is a dramatic difference in the shift of the peak of the Bragg spectra, compared to that based on a structureless atom model. The result is compatible with the experimental results of Papp [Phys. Rev. LettPRLTAO0031-900710.1103/PhysRevLett.101.135301 101, 135301 (2008)] for Bragg scattering from a nonuniform condensate.
Geostatistical joint inversion of seismic and potential field methods
NASA Astrophysics Data System (ADS)
Shamsipour, Pejman; Chouteau, Michel; Giroux, Bernard
2016-04-01
Interpretation of geophysical data needs to integrate different types of information to make the proposed model geologically realistic. Multiple data sets can reduce uncertainty and non-uniqueness present in separate geophysical data inversions. Seismic data can play an important role in mineral exploration, however processing and interpretation of seismic data is difficult due to complexity of hard-rock geology. On the other hand, the recovered model from potential field methods is affected by inherent non uniqueness caused by the nature of the physics and by underdetermination of the problem. Joint inversion of seismic and potential field data can mitigate weakness of separate inversion of these methods. A stochastic joint inversion method based on geostatistical techniques is applied to estimate density and velocity distributions from gravity and travel time data. The method fully integrates the physical relations between density-gravity, on one hand, and slowness-travel time, on the other hand. As a consequence, when the data are considered noise-free, the responses from the inverted slowness and density data exactly reproduce the observed data. The required density and velocity auto- and cross-covariance are assumed to follow a linear model of coregionalization (LCM). The recent development of nonlinear model of coregionalization could also be applied if needed. The kernel function for the gravity method is obtained by the closed form formulation. For ray tracing, we use the shortest-path methods (SPM) to calculate the operation matrix. The jointed inversion is performed on structured grid; however, it is possible to extend it to use unstructured grid. The method is tested on two synthetic models: a model consisting of two objects buried in a homogeneous background and a model with stochastic distribution of parameters. The results illustrate the capability of the method to improve the inverted model compared to the separate inverted models with either gravity
Light Field Imaging Based Accurate Image Specular Highlight Removal.
Wang, Haoqian; Xu, Chenxue; Wang, Xingzheng; Zhang, Yongbing; Peng, Bo
2016-01-01
Specular reflection removal is indispensable to many computer vision tasks. However, most existing methods fail or degrade in complex real scenarios for their individual drawbacks. Benefiting from the light field imaging technology, this paper proposes a novel and accurate approach to remove specularity and improve image quality. We first capture images with specularity by the light field camera (Lytro ILLUM). After accurately estimating the image depth, a simple and concise threshold strategy is adopted to cluster the specular pixels into "unsaturated" and "saturated" category. Finally, a color variance analysis of multiple views and a local color refinement are individually conducted on the two categories to recover diffuse color information. Experimental evaluation by comparison with existed methods based on our light field dataset together with Stanford light field archive verifies the effectiveness of our proposed algorithm. PMID:27253083
Light Field Imaging Based Accurate Image Specular Highlight Removal
Wang, Haoqian; Xu, Chenxue; Wang, Xingzheng; Zhang, Yongbing; Peng, Bo
2016-01-01
Specular reflection removal is indispensable to many computer vision tasks. However, most existing methods fail or degrade in complex real scenarios for their individual drawbacks. Benefiting from the light field imaging technology, this paper proposes a novel and accurate approach to remove specularity and improve image quality. We first capture images with specularity by the light field camera (Lytro ILLUM). After accurately estimating the image depth, a simple and concise threshold strategy is adopted to cluster the specular pixels into “unsaturated” and “saturated” category. Finally, a color variance analysis of multiple views and a local color refinement are individually conducted on the two categories to recover diffuse color information. Experimental evaluation by comparison with existed methods based on our light field dataset together with Stanford light field archive verifies the effectiveness of our proposed algorithm. PMID:27253083
Method of using triaxial magnetic fields for making particle structures
Martin, James E.; Anderson, Robert A.; Williamson, Rodney L.
2005-01-18
A method of producing three-dimensional particle structures with enhanced magnetic susceptibility in three dimensions by applying a triaxial energetic field to a magnetic particle suspension and subsequently stabilizing said particle structure. Combinations of direct current and alternating current fields in three dimensions produce particle gel structures, honeycomb structures, and foam-like structures.
Field Comparison of Methods for Measuring Soil CO2 Flux
Technology Transfer Automated Retrieval System (TEKTRAN)
A variety of techniques are available for measurement of soil carbon dioxide (CO2) flux in the field, and each method has inherent advantages and disadvantages. On five dates in October, 2005 we measured soil CO2 emissions in a central Iowa soybean field using: i)eddy covariance, ii)a commercially a...
FIELD ANALYTICAL SCREENING PROGRAM: PCB METHOD - INNOVATIVE TECHNOLOGY REPORT
This innovative technology evaluation report (ITER) presents information on the demonstration of the U.S. Environmental Protection Agency (EPA) Region 7 Superfund Field Analytical Screening Program (FASP) method for determining polychlorinated biphenyl (PCB) contamination in soil...
New light field camera based on physical based rendering tracing
NASA Astrophysics Data System (ADS)
Chung, Ming-Han; Chang, Shan-Ching; Lee, Chih-Kung
2014-03-01
Even though light field technology was first invented more than 50 years ago, it did not gain popularity due to the limitation imposed by the computation technology. With the rapid advancement of computer technology over the last decade, the limitation has been uplifted and the light field technology quickly returns to the spotlight of the research stage. In this paper, PBRT (Physical Based Rendering Tracing) was introduced to overcome the limitation of using traditional optical simulation approach to study the light field camera technology. More specifically, traditional optical simulation approach can only present light energy distribution but typically lack the capability to present the pictures in realistic scenes. By using PBRT, which was developed to create virtual scenes, 4D light field information was obtained to conduct initial data analysis and calculation. This PBRT approach was also used to explore the light field data calculation potential in creating realistic photos. Furthermore, we integrated the optical experimental measurement results with PBRT in order to place the real measurement results into the virtually created scenes. In other words, our approach provided us with a way to establish a link of virtual scene with the real measurement results. Several images developed based on the above-mentioned approaches were analyzed and discussed to verify the pros and cons of the newly developed PBRT based light field camera technology. It will be shown that this newly developed light field camera approach can circumvent the loss of spatial resolution associated with adopting a micro-lens array in front of the image sensors. Detailed operational constraint, performance metrics, computation resources needed, etc. associated with this newly developed light field camera technique were presented in detail.
New Method for Solving Inductive Electric Fields in the Ionosphere
NASA Astrophysics Data System (ADS)
Vanhamäki, H.
2005-12-01
We present a new method for calculating inductive electric fields in the ionosphere. It is well established that on large scales the ionospheric electric field is a potential field. This is understandable, since the temporal variations of large scale current systems are generally quite slow, in the timescales of several minutes, so inductive effects should be small. However, studies of Alfven wave reflection have indicated that in some situations inductive phenomena could well play a significant role in the reflection process, and thus modify the nature of ionosphere-magnetosphere coupling. The input to our calculation method are the time series of the potential part of the ionospheric electric field together with the Hall and Pedersen conductances. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called Cartesian Elementary Current Systems (CECS). This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfven wave reflection from uniformly conducting ionosphere.
NASA Technical Reports Server (NTRS)
Baxes, Gregory A. (Inventor); Linger, Timothy C. (Inventor)
2011-01-01
Systems and methods are provided for progressive mesh storage and reconstruction using wavelet-encoded height fields. A method for progressive mesh storage includes reading raster height field data, and processing the raster height field data with a discrete wavelet transform to generate wavelet-encoded height fields. In another embodiment, a method for progressive mesh storage includes reading texture map data, and processing the texture map data with a discrete wavelet transform to generate wavelet-encoded texture map fields. A method for reconstructing a progressive mesh from wavelet-encoded height field data includes determining terrain blocks, and a level of detail required for each terrain block, based upon a viewpoint. Triangle strip constructs are generated from vertices of the terrain blocks, and an image is rendered utilizing the triangle strip constructs. Software products that implement these methods are provided.
NASA Technical Reports Server (NTRS)
Baxes, Gregory A. (Inventor)
2010-01-01
Systems and methods are provided for progressive mesh storage and reconstruction using wavelet-encoded height fields. A method for progressive mesh storage includes reading raster height field data, and processing the raster height field data with a discrete wavelet transform to generate wavelet-encoded height fields. In another embodiment, a method for progressive mesh storage includes reading texture map data, and processing the texture map data with a discrete wavelet transform to generate wavelet-encoded texture map fields. A method for reconstructing a progressive mesh from wavelet-encoded height field data includes determining terrain blocks, and a level of detail required for each terrain block, based upon a viewpoint. Triangle strip constructs are generated from vertices of the terrain blocks, and an image is rendered utilizing the triangle strip constructs. Software products that implement these methods are provided.
Using force fields methods for locating transition structures
NASA Astrophysics Data System (ADS)
Jensen, Frank
2003-11-01
A previously proposed strategy of using force field methods for generating approximations to the geometry of transition structures is extended to also estimating an approximate Hessian matrix. These two components allow an automated method for locating first order saddle points, which is an essential requisite for studying chemical reactions of systems with many degrees of freedom. The efficiency of using an approximate force field Hessian matrix for initiating the geometry optimization is compared with the use of an exact Hessian. The force field Hessian in general requires more geometry steps to converge, but the additional computational cost is offset by the savings from not calculating the exact Hessian at the initial geometry.
A cavitation model based on Eulerian stochastic fields
NASA Astrophysics Data System (ADS)
Magagnato, F.; Dumond, J.
2013-12-01
Non-linear phenomena can often be described using probability density functions (pdf) and pdf transport models. Traditionally the simulation of pdf transport requires Monte-Carlo codes based on Lagrangian "particles" or prescribed pdf assumptions including binning techniques. Recently, in the field of combustion, a novel formulation called the stochastic-field method solving pdf transport based on Eulerian fields has been proposed which eliminates the necessity to mix Eulerian and Lagrangian techniques or prescribed pdf assumptions. In the present work, for the first time the stochastic-field method is applied to multi-phase flow and in particular to cavitating flow. To validate the proposed stochastic-field cavitation model, two applications are considered. Firstly, sheet cavitation is simulated in a Venturi-type nozzle. The second application is an innovative fluidic diode which exhibits coolant flashing. Agreement with experimental results is obtained for both applications with a fixed set of model constants. The stochastic-field cavitation model captures the wide range of pdf shapes present at different locations.
Force-free magnetic fields - The magneto-frictional method
NASA Technical Reports Server (NTRS)
Yang, W. H.; Sturrock, P. A.; Antiochos, S. K.
1986-01-01
The problem under discussion is that of calculating magnetic field configurations in which the Lorentz force j x B is everywhere zero, subject to specified boundary conditions. We choose to represent the magnetic field in terms of Clebsch variables in the form B = grad alpha x grad beta. These variables are constant on any field line so that each field line is labeled by the corresponding values of alpha and beta. When the field is described in this way, the most appropriate choice of boundary conditions is to specify the values of alpha and beta on the bounding surface. We show that such field configurations may be calculated by a magneto-frictional method. We imagine that the field lines move through a stationary medium, and that each element of magnetic field is subject to a frictional force parallel to and opposing the velocity of the field line. This concept leads to an iteration procedure for modifying the variables alpha and beta, that tends asymptotically towards the force-free state. We apply the method first to a simple problem in two rectangular dimensions, and then to a problem of cylindrical symmetry that was previously discussed by Barnes and Sturrock (1972). In one important respect, our new results differ from the earlier results of Barnes and Sturrock, and we conclude that the earlier article was in error.
Comparison of electric field exposure measurement methods under power lines.
Korpinen, Leena; Kuisti, Harri; Tarao, Hiroo; Pääkkönen, Rauno; Elovaara, Jarmo
2014-01-01
The object of the study was to investigate extremely low frequency (ELF) electric field exposure measurement methods under power lines. The authors compared two different methods under power lines: in Method A, the sensor was placed on a tripod; and Method B required the measurer to hold the meter horizontally so that the distance from him/her was at least 1.5 m. The study includes 20 measurements in three places under 400 kV power lines. The authors used two commercial three-axis meters, EFA-3 and EFA-300. In statistical analyses, they did not find significant differences between Methods A and B. However, in the future, it is important to take into account that measurement methods can, in some cases, influence ELF electric field measurement results, and it is important to report the methods used so that it is possible to repeat the measurements.
FIELD ANALYTICAL SCREENING PROGRAM: PCP METHOD - INNOVATIVE TECHNOLOGY EVALUATION REPORT
The Field Analytical Screening Program (FASP) pentachlorophenol (PCP) method uses a gas chromatograph (GC) equipped with a megabore capillary column and flame ionization detector (FID) and electron capture detector (ECD) to identify and quantify PCP. The FASP PCP method is design...
Geochemical field method for determination of nickel in plants
Reichen, L.E.
1951-01-01
The use of biogeochemical data in prospecting for nickel emphasizes the need for a simple, moderately accurate field method for the determination of nickel in plants. In order to follow leads provided by plants of unusual nickel content without loss of time, the plants should be analyzed and the results given to the field geologist promptly. The method reported in this paper was developed to meet this need. Speed is acquired by elimination of the customary drying and controlled ashing; the fresh vegetation is ashed in an open dish over a gasoline stove. The ash is put into solution with hydrochloric acid and the solution buffered. A chromograph is used to make a confined spot with an aliquot of the ash solution on dimethylglyoxime reagent paper. As little as 0.025% nickel in plant ash can be determined. With a simple modification, 0.003% can be detected. Data are given comparing the results obtained by an accepted laboratory procedure. Results by the field method are within 30% of the laboratory values. The field method for nickel in plants meets the requirements of biogeochemical prospecting with respect to accuracy, simplicity, speed, and ease of performance in the field. With experience, an analyst can make 30 determinations in an 8-hour work day in the field.
[Development and application of electroanalytical methods in biomedical fields].
Kusu, Fumiyo
2015-01-01
To summarize our electroanalytical research in the biomedical field over the past 43 years, this review describes studies on specular reflection measurement, redox potential determination, amperometric acid sensing, HPLC with electrochemical detection, and potential oscillation across a liquid membrane. The specular reflection method was used for clarifying the adsorption of neurotransmitters and their related drugs onto a gold electrode and the interaction between dental alloys and compound iodine glycerin. A voltammetric screening test using a redox potential for the antioxidative effect of flavonoids was proposed. Amperometric acid sensing based on the measurement of the reduction prepeak current of 2-methyl-1,4-naphthoquinone (VK3) or 3,5-di-tert-buty1-1,2-benzoquinone (DBBQ) was applied to determine acid values of fats and oils, titrable acidity of coffee, and enzyme activity of lipase, free fatty acids (FFAs) in serum, short-chain fatty acids in feces, etc. The electrode reactions of phenothiazines, catechins, and cholesterol were applied to biomedical analysis using HPLC with electrochemical detection. A three-channel electrochemical detection system was utilized for the sensitive determination of redox compounds in Chinese herbal medicines. The behavior of barbituric acid derivatives was examined based on potential oscillation measurements.
Field calibration of binocular stereo vision based on fast reconstruction of 3D control field
NASA Astrophysics Data System (ADS)
Zhang, Haijun; Liu, Changjie; Fu, Luhua; Guo, Yin
2015-08-01
Construction of high-speed railway in China has entered a period of rapid growth. To accurately and quickly obtain the dynamic envelope curve of high-speed vehicle is an important guarantee for safe driving. The measuring system is based on binocular stereo vision. Considering the difficulties in field calibration such as environmental changes and time limits, carried out a field calibration method based on fast reconstruction of three-dimensional control field. With the rapid assembly of pre-calibrated three-dimensional control field, whose coordinate accuracy is guaranteed by manufacture accuracy and calibrated by V-STARS, two cameras take a quick shot of it at the same time. The field calibration parameters are then solved by the method combining linear solution with nonlinear optimization. Experimental results showed that the measurement accuracy can reach up to +/- 0.5mm, and more importantly, in the premise of guaranteeing accuracy, the speed of the calibration and the portability of the devices have been improved considerably.
Stevens, Fred J.
1992-01-01
A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.
Direct field method for root biomass quantification in agroecosystems.
Frasier, Ileana; Noellemeyer, Elke; Fernández, Romina; Quiroga, Alberto
2016-01-01
The present article describes a field auger sampling method for row-crop root measurements. In agroecosystems where crops are planted in a specific design (row crops), sampling procedures for root biomass quantification need to consider the spatial variability of the root system. This article explains in detail how to sample and calculate root biomass considering the sampling position in the field and the differential weight of the root biomass in the inter-row compared to the crop row when expressing data per area unit. This method is highly reproducible in the field and requires no expensive equipment and/or special skills. It proposes to use a narrow auger thus reducing field labor with less destructive sampling, and decreases laboratory time because samples are smaller. The small sample size also facilitates the washing and root separation with tweezers. This method is suitable for either winter- or summer crop roots. •Description of a direct field method for row-crop root measurements.•Description of data calculation for total root-biomass estimation per unit area.•The proposed method is simple, less labor- and less time consuming. PMID:27630821
A regularization method for extrapolation of solar potential magnetic fields
NASA Technical Reports Server (NTRS)
Gary, G. A.; Musielak, Z. E.
1992-01-01
The mathematical basis of a Tikhonov regularization method for extrapolating the chromospheric-coronal magnetic field using photospheric vector magnetograms is discussed. The basic techniques show that the Cauchy initial value problem can be formulated for potential magnetic fields. The potential field analysis considers a set of linear, elliptic partial differential equations. It is found that, by introducing an appropriate smoothing of the initial data of the Cauchy potential problem, an approximate Fourier integral solution is found, and an upper bound to the error in the solution is derived. This specific regularization technique, which is a function of magnetograph measurement sensitivities, provides a method to extrapolate the potential magnetic field above an active region into the chromosphere and low corona.
Method of determining interwell oil field fluid saturation distribution
Donaldson, Erle C.; Sutterfield, F. Dexter
1981-01-01
A method of determining the oil and brine saturation distribution in an oil field by taking electrical current and potential measurements among a plurality of open-hole wells geometrically distributed throughout the oil field. Poisson's equation is utilized to develop fluid saturation distributions from the electrical current and potential measurement. Both signal generating equipment and chemical means are used to develop current flow among the several open-hole wells.
E-field extraction from Hx- and Hy- near field values by using plane wave spectrum method
NASA Astrophysics Data System (ADS)
Ravelo, B.; Riah, Z.; Baudry, D.; Mazari, B.
2011-01-01
This paper deals with a technique for calculating the 3D E-field components knowing only the two components (Hx and Hy) of the H-field in near-zone. The originality of the under study technique lies on the possibility to take into account the evanescent wave influences. The presented E-field extraction process is based on the exploitation of the Maxwell-Ampere relation combined with the plane wave spectrum (PWS) method. The efficiency of the proposed technique is evidenced by comparing the E-field deduced from H-field and the own E-field radiated by the association of electrical- and also magnetic- elementary dipoles in different configurations by using Matlab text programming environment. In addition, as a concrete demonstrator, the concept was also validated with the computation of EM-wave radiated by an open-end microstrip transmission line. As result of comparison, very good agreement between the exact E-field and that one extracted from the H-field was realized by considering the near-field scanned at the height, z = 5 mm and 8 mm above the under test structure at the operating frequency, f = 1 GHz. The presented technique can simplify the difficulties about the E-near-field measurement in EMC applications.
Phase unwrapping using region-based markov random field model.
Dong, Ying; Ji, Jim
2010-01-01
Phase unwrapping is a classical problem in Magnetic Resonance Imaging (MRI), Interferometric Synthetic Aperture Radar and Sonar (InSAR/InSAS), fringe pattern analysis, and spectroscopy. Although many methods have been proposed to address this problem, robust and effective phase unwrapping remains a challenge. This paper presents a novel phase unwrapping method using a region-based Markov Random Field (MRF) model. Specifically, the phase image is segmented into regions within which the phase is not wrapped. Then, the phase image is unwrapped between different regions using an improved Highest Confidence First (HCF) algorithm to optimize the MRF model. The proposed method has desirable theoretical properties as well as an efficient implementation. Simulations and experimental results on MRI images show that the proposed method provides similar or improved phase unwrapping than Phase Unwrapping MAx-flow/min-cut (PUMA) method and ZpM method.
Phase unwrapping using region-based markov random field model.
Dong, Ying; Ji, Jim
2010-01-01
Phase unwrapping is a classical problem in Magnetic Resonance Imaging (MRI), Interferometric Synthetic Aperture Radar and Sonar (InSAR/InSAS), fringe pattern analysis, and spectroscopy. Although many methods have been proposed to address this problem, robust and effective phase unwrapping remains a challenge. This paper presents a novel phase unwrapping method using a region-based Markov Random Field (MRF) model. Specifically, the phase image is segmented into regions within which the phase is not wrapped. Then, the phase image is unwrapped between different regions using an improved Highest Confidence First (HCF) algorithm to optimize the MRF model. The proposed method has desirable theoretical properties as well as an efficient implementation. Simulations and experimental results on MRI images show that the proposed method provides similar or improved phase unwrapping than Phase Unwrapping MAx-flow/min-cut (PUMA) method and ZpM method. PMID:21096819
Method of improving field emission characteristics of diamond thin films
Krauss, Alan R.; Gruen, Dieter M.
1999-01-01
A method of preparing diamond thin films with improved field emission properties. The method includes preparing a diamond thin film on a substrate, such as Mo, W, Si and Ni. An atmosphere of hydrogen (molecular or atomic) can be provided above the already deposited film to form absorbed hydrogen to reduce the work function and enhance field emission properties of the diamond film. In addition, hydrogen can be absorbed on intergranular surfaces to enhance electrical conductivity of the diamond film. The treated diamond film can be part of a microtip array in a flat panel display.
Method of improving field emission characteristics of diamond thin films
Krauss, A.R.; Gruen, D.M.
1999-05-11
A method of preparing diamond thin films with improved field emission properties is disclosed. The method includes preparing a diamond thin film on a substrate, such as Mo, W, Si and Ni. An atmosphere of hydrogen (molecular or atomic) can be provided above the already deposited film to form absorbed hydrogen to reduce the work function and enhance field emission properties of the diamond film. In addition, hydrogen can be absorbed on intergranular surfaces to enhance electrical conductivity of the diamond film. The treated diamond film can be part of a microtip array in a flat panel display. 3 figs.
NASA Technical Reports Server (NTRS)
Glatt, C. R.; Hague, D. S.; Reiners, S. J.
1975-01-01
A computerized procedure for predicting sonic boom from experimental near-field overpressure data has been developed. The procedure extrapolates near-field pressure signatures for a specified flight condition to the ground by the Thomas method. Near-field pressure signatures are interpolated from a data base of experimental pressure signatures. The program is an independently operated ODIN (Optimal Design Integration) program which obtains flight path information from other ODIN programs or from input.
Localized Dictionaries Based Orientation Field Estimation for Latent Fingerprints.
Xiao Yang; Jianjiang Feng; Jie Zhou
2014-05-01
Dictionary based orientation field estimation approach has shown promising performance for latent fingerprints. In this paper, we seek to exploit stronger prior knowledge of fingerprints in order to further improve the performance. Realizing that ridge orientations at different locations of fingerprints have different characteristics, we propose a localized dictionaries-based orientation field estimation algorithm, in which noisy orientation patch at a location output by a local estimation approach is replaced by real orientation patch in the local dictionary at the same location. The precondition of applying localized dictionaries is that the pose of the latent fingerprint needs to be estimated. We propose a Hough transform-based fingerprint pose estimation algorithm, in which the predictions about fingerprint pose made by all orientation patches in the latent fingerprint are accumulated. Experimental results on challenging latent fingerprint datasets show the proposed method outperforms previous ones markedly.
Lagrangian based methods for coherent structure detection.
Allshouse, Michael R; Peacock, Thomas
2015-09-01
There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We present a review of four approaches and demonstrate the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other two approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also present a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows. PMID:26428570
Lagrangian based methods for coherent structure detection
Allshouse, Michael R.; Peacock, Thomas
2015-09-15
There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We present a review of four approaches and demonstrate the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other two approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also present a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows.
NASA Technical Reports Server (NTRS)
Ransom, Jonathan B.
2002-01-01
A multifunctional interface method with capabilities for variable-fidelity modeling and multiple method analysis is presented. The methodology provides an effective capability by which domains with diverse idealizations can be modeled independently to exploit the advantages of one approach over another. The multifunctional method is used to couple independently discretized subdomains, and it is used to couple the finite element and the finite difference methods. The method is based on a weighted residual variational method and is presented for two-dimensional scalar-field problems. A verification test problem and a benchmark application are presented, and the computational implications are discussed.
NASA Astrophysics Data System (ADS)
Frassinetti, L.; Olofsson, K. E. J.; Fridström, R.; Setiadi, A. C.; Brunsell, P. R.; Volpe, F. A.; Drake, J.
2013-08-01
A new method for the estimate of the wall diffusion time of non-axisymmetric fields is developed. The method based on rotating external fields and on the measurement of the wall frequency response is developed and tested in EXTRAP T2R. The method allows the experimental estimate of the wall diffusion time for each Fourier harmonic and the estimate of the wall diffusion toroidal asymmetries. The method intrinsically considers the effects of three-dimensional structures and of the shell gaps. Far from the gaps, experimental results are in good agreement with the diffusion time estimated with a simple cylindrical model that assumes a homogeneous wall. The method is also applied with non-standard configurations of the coil array, in order to mimic tokamak-relevant settings with a partial wall coverage and active coils of large toroidal extent. The comparison with the full coverage results shows good agreement if the effects of the relevant sidebands are considered.
Accurate force fields and methods for modelling organic molecular crystals at finite temperatures.
Nyman, Jonas; Pundyke, Orla Sheehan; Day, Graeme M
2016-06-21
We present an assessment of the performance of several force fields for modelling intermolecular interactions in organic molecular crystals using the X23 benchmark set. The performance of the force fields is compared to several popular dispersion corrected density functional methods. In addition, we present our implementation of lattice vibrational free energy calculations in the quasi-harmonic approximation, using several methods to account for phonon dispersion. This allows us to also benchmark the force fields' reproduction of finite temperature crystal structures. The results demonstrate that anisotropic atom-atom multipole-based force fields can be as accurate as several popular DFT-D methods, but have errors 2-3 times larger than the current best DFT-D methods. The largest error in the examined force fields is a systematic underestimation of the (absolute) lattice energy.
Design of traveling wave tubes based on field theory
Vanderplaats, N.R.; Kodis, M.A. . Vacuum Electronics Branch); Freund, H.P. )
1994-07-01
A method is described for the design of helix traveling wave tubes (TWT) which is based on the linear field analysis of the coupled beam-wave system. The dispersion relations are obtained by matching of radial admittances at boundaries instead of the individual field components. This approach provides flexibility in modeling various beam and circuit configurations with relative ease by choosing the appropriate admittance functions for each case. The method is illustrated for the case of a solid beam inside a sheath helix which is loaded externally by lossy dielectric material, a conducting cylinder, and axial vanes. Extension of the analysis to include a thin tape helix model is anticipated in the near future. The TWT model may be divided into axial regions to include velocity tapers, lossy materials and severs, with the helix geometry in each region varied arbitrarily. The relations between the ac velocities, current densities, and axial electric fields are used to derive a general expression for the new amplitudes of the three forward waves at each axial boundary. The sum of the fields for the three forward waves (two waves in a drift region) is followed to the circuit output. Numerical results of the field analysis are compared with the coupled-mode Pierce theory. A method is suggested for applying the field analysis to accurate design of practical TWT's that have a more complex circuit geometry, which starts with a simple measurement of the dispersion of the helix circuit. The field analysis may then be used to generate a circuit having properties very nearly equivalent to those of the actual circuit.
Field-based physiological testing of wheelchair athletes.
Goosey-Tolfrey, Victoria L; Leicht, Christof A
2013-02-01
The volume of literature on field-based physiological testing of wheelchair sports, such as basketball, rugby and tennis, is considerably smaller when compared with that available for individuals and team athletes in able-bodied (AB) sports. In analogy to the AB literature, it is recognized that performance in wheelchair sports not only relies on fitness, but also sport-specific skills, experience and technical proficiency. However, in contrast to AB sports, two major components contribute towards 'wheeled sports' performance, which are the athlete and the wheelchair. It is the interaction of these two that enable wheelchair propulsion and the sporting movements required within a given sport. Like any other athlete, participants of wheelchair sports are looking for efficient ways to train and/or analyse their technique and fitness to improve their performance. Consequently, laboratory and/or field-based physiological monitoring tools used at regular intervals at key time points throughout the year must be considered to help with training evaluation. The present review examines methods available in the literature to assess wheelchair sports fitness in a field-based environment, with special attention on outcome variables, validity and reliability issues, and non-physiological influences on performance. It also lays out the context of field-based testing by providing details about the Paralympic court sports and the impacts of a disability on sporting performance. Due to the limited availability of specialized equipment for testing wheelchair-dependent participants in the laboratory, the adoption of field-based testing has become the preferred option by team coaches of wheelchair athletes. An obvious advantage of field-based testing is that large groups of athletes can be tested in less time. Furthermore, athletes are tested in their natural environment (using their normal sports wheelchair set-up and floor surface), potentially making the results of such testing
Field-based physiological testing of wheelchair athletes.
Goosey-Tolfrey, Victoria L; Leicht, Christof A
2013-02-01
The volume of literature on field-based physiological testing of wheelchair sports, such as basketball, rugby and tennis, is considerably smaller when compared with that available for individuals and team athletes in able-bodied (AB) sports. In analogy to the AB literature, it is recognized that performance in wheelchair sports not only relies on fitness, but also sport-specific skills, experience and technical proficiency. However, in contrast to AB sports, two major components contribute towards 'wheeled sports' performance, which are the athlete and the wheelchair. It is the interaction of these two that enable wheelchair propulsion and the sporting movements required within a given sport. Like any other athlete, participants of wheelchair sports are looking for efficient ways to train and/or analyse their technique and fitness to improve their performance. Consequently, laboratory and/or field-based physiological monitoring tools used at regular intervals at key time points throughout the year must be considered to help with training evaluation. The present review examines methods available in the literature to assess wheelchair sports fitness in a field-based environment, with special attention on outcome variables, validity and reliability issues, and non-physiological influences on performance. It also lays out the context of field-based testing by providing details about the Paralympic court sports and the impacts of a disability on sporting performance. Due to the limited availability of specialized equipment for testing wheelchair-dependent participants in the laboratory, the adoption of field-based testing has become the preferred option by team coaches of wheelchair athletes. An obvious advantage of field-based testing is that large groups of athletes can be tested in less time. Furthermore, athletes are tested in their natural environment (using their normal sports wheelchair set-up and floor surface), potentially making the results of such testing
Background field method and the cohomology of renormalization
NASA Astrophysics Data System (ADS)
Anselmi, Damiano
2016-03-01
Using the background field method and the Batalin-Vilkovisky formalism, we prove a key theorem on the cohomology of perturbatively local functionals of arbitrary ghost numbers in renormalizable and nonrenormalizable quantum field theories whose gauge symmetries are general covariance, local Lorentz symmetry, non-Abelian Yang-Mills symmetries and Abelian gauge symmetries. Interpolating between the background field approach and the usual, nonbackground approach by means of a canonical transformation, we take advantage of the properties of both approaches and prove that a closed functional is the sum of an exact functional plus a functional that depends only on the physical fields and possibly the ghosts. The assumptions of the theorem are the mathematical versions of general properties that characterize the counterterms and the local contributions to the potential anomalies. This makes the outcome a theorem on the cohomology of renormalization, rather than the whole local cohomology. The result supersedes numerous involved arguments that are available in the literature.
Field Science Ethnography: Methods For Systematic Observation on an Expedition
NASA Technical Reports Server (NTRS)
Clancey, William J.; Clancy, Daniel (Technical Monitor)
2001-01-01
The Haughton-Mars expedition is a multidisciplinary project, exploring an impact crater in an extreme environment to determine how people might live and work on Mars. The expedition seeks to understand and field test Mars facilities, crew roles, operations, and computer tools. I combine an ethnographic approach to establish a baseline understanding of how scientists prefer to live and work when relatively unemcumbered, with a participatory design approach of experimenting with procedures and tools in the context of use. This paper focuses on field methods for systematically recording and analyzing the expedition's activities. Systematic photography and time-lapse video are combined with concept mapping to organize and present information. This hybrid approach is generally applicable to the study of modern field expeditions having a dozen or more multidisciplinary participants, spread over a large terrain during multiple field seasons.
Hyperspectral Imaging and Related Field Methods: Building the Science
NASA Technical Reports Server (NTRS)
Goetz, Alexander F. H.; Steffen, Konrad; Wessman, Carol
1999-01-01
The proposal requested funds for the computing power to bring hyperspectral image processing into undergraduate and graduate remote sensing courses. This upgrade made it possible to handle more students in these oversubscribed courses and to enhance CSES' summer short course entitled "Hyperspectral Imaging and Data Analysis" provided for government, industry, university and military. Funds were also requested to build field measurement capabilities through the purchase of spectroradiometers, canopy radiation sensors and a differential GPS system. These instruments provided systematic and complete sets of field data for the analysis of hyperspectral data with the appropriate radiometric and wavelength calibration as well as atmospheric data needed for application of radiative transfer models. The proposed field equipment made it possible to team-teach a new field methods course, unique in the country, that took advantage of the expertise of the investigators rostered in three different departments, Geology, Geography and Biology.
Work function measurements by the field emission retarding potential method
NASA Technical Reports Server (NTRS)
Swanson, L. W.; Strayer, R. W.; Mackie, W. A.
1971-01-01
Using the field emission retarding potential method true work functions have been measured for the following monocrystalline substrates: W(110), W(111), W(100), Nb(100), Ni(100), Cu(100), Ir(110) and Ir(111). The electron elastic and inelastic reflection coefficients from several of these surfaces have also been examined near zero primary beam energy.
Unsaturated soil hydraulic conductivity: The field infiltrometer method
Technology Transfer Automated Retrieval System (TEKTRAN)
Theory: Field methods to measure the unsaturated soil hydraulic conductivity assume presence of steady-state water flow. Soil infiltrometers are desired to apply water onto the soil surface at constant negative pressure. Water is applied to the soil from the Marriott device through a porous membrane...
Susan S. Sorini; John F. Schabron
1997-04-01
A new screening method for fuel contamination in soils was recently developed as American Society for Testing and Materials (ASTM) Method D-583 1-95, Standard Test Method for Screening Fuels in Soils. This method uses low-toxicity chemicals and can be used to screen organic-rich soils. In addition, it is fast, easy, and inexpensive to perform. The screening method calls for extracting a sample of soil with isopropyl alcohol following treatment with calcium oxide. The resulting extract is filtered, and the ultraviolet absorbance of the extract is measured at 254 nm. Depending on the available information concerning the contaminant fuel type and availability of the contaminant fuel for calibration, the method can be used to determine the approximate concentration of fuel contamination, an estimated value of fuel contamination, or an indication of the presence or absence of fuel contamination. Fuels containing aromatic compounds, such as diesel fuel and gasoline, as well as other aromatic-containing hydrocarbon materials, such as motor oil, crude oil, and coal oil, can be determined. The screening method for fuels in soils was evaluated by conducting a collaborative study on the method and by using the method to screen soil samples at an actual field site. In the collaborative study, a sand and an organic soil spiked with various concentrations of diesel fuel were tested. Data from the collaborative study were used to determine the reproducibility (between participants) and repeatability (within participant) precision of the method for screening the test materials. The collaborative study data also provide information on the performance of portable field equipment versus laboratory equipment for performing the screening method and a comparison of diesel concentration values determined using the screening method versus a laboratory method. Data generated using the method to screen soil samples in the field provide information on the performance of the method in
Field Deployable Method for Arsenic Speciation in Water
Voice, Thomas C.; Flores del Pino, Lisveth V.; Havezov, Ivan; Long, David T.
2010-01-01
Contamination of drinking water supplies by arsenic is a world-wide problem. Total arsenic measurements are commonly used to investigate and regulate arsenic in water, but it is well understood that arsenic occurs in several chemical forms, and these exhibit different toxicities. It is problematic to use laboratory-based speciation techniques to assess exposure as it has been suggested that the distribution of species is not stable during transport in some types of samples. A method was developed in this study for the on-site speciation of the most toxic dissolved arsenic species: As (III), As (V), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA). Development criteria included ease of use under field conditions, applicable at levels of concern for drinking water, and analytical performance. The approach is based on selective retention of arsenic species on specific ion-exchange chromatography cartridges followed by selective elution and quantification using graphite furnace atomic absorption spectroscopy. Water samples can be delivered to a set of three cartridges using either syringes or peristaltic pumps. Species distribution is stable at this point, and the cartridges can be transported to the laboratory for elution and quantitative analysis. A set of ten replicate spiked samples of each compound, having concentrations between 1 and 60 µg/L, were analyzed. Arsenic recoveries ranged from 78–112 % and relative standard deviations were generally below 10%. Resolution between species was shown to be outstanding, with the only limitation being that the capacity for As (V) was limited to approximately 50 µg/L. This could be easily remedied by changes in either cartridge design, or the extraction procedure. Recoveries were similar for two spiked hard groundwater samples indicating that dissolved minerals are not likely to be problematic. These results suggest that this methodology can be use for analysis of the four primary arsenic species of concern in
Field Deployable Method for Arsenic Speciation in Water.
Voice, Thomas C; Flores Del Pino, Lisveth V; Havezov, Ivan; Long, David T
2011-01-01
Contamination of drinking water supplies by arsenic is a world-wide problem. Total arsenic measurements are commonly used to investigate and regulate arsenic in water, but it is well understood that arsenic occurs in several chemical forms, and these exhibit different toxicities. It is problematic to use laboratory-based speciation techniques to assess exposure as it has been suggested that the distribution of species is not stable during transport in some types of samples. A method was developed in this study for the on-site speciation of the most toxic dissolved arsenic species: As (III), As (V), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA). Development criteria included ease of use under field conditions, applicable at levels of concern for drinking water, and analytical performance.The approach is based on selective retention of arsenic species on specific ion-exchange chromatography cartridges followed by selective elution and quantification using graphite furnace atomic absorption spectroscopy. Water samples can be delivered to a set of three cartridges using either syringes or peristaltic pumps. Species distribution is stable at this point, and the cartridges can be transported to the laboratory for elution and quantitative analysis. A set of ten replicate spiked samples of each compound, having concentrations between 1 and 60 µg/L, were analyzed. Arsenic recoveries ranged from 78-112 % and relative standard deviations were generally below 10%. Resolution between species was shown to be outstanding, with the only limitation being that the capacity for As (V) was limited to approximately 50 µg/L. This could be easily remedied by changes in either cartridge design, or the extraction procedure. Recoveries were similar for two spiked hard groundwater samples indicating that dissolved minerals are not likely to be problematic. These results suggest that this methodology can be use for analysis of the four primary arsenic species of concern in
Field deployable method for arsenic speciation in water
NASA Astrophysics Data System (ADS)
Voice, Thomas C.; Flores del Pino, Lisveth V.; Havezov, Ivan; Long, David T.
Contamination of drinking water supplies by arsenic is a world-wide problem. Total arsenic measurements are commonly used to investigate and regulate arsenic in water, but it is well understood that arsenic occurs in several chemical forms, and these exhibit different toxicities. It is problematic to use laboratory-based speciation techniques to assess exposure as it has been suggested that the distribution of species is not stable during transport in some types of samples. A method was developed in this study for the on-site speciation of the most toxic dissolved arsenic species: As (III), As (V), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA). Development criteria included ease of use under field conditions, applicable at levels of concern for drinking water, and analytical performance. The approach is based on selective retention of arsenic species on specific ion-exchange chromatography cartridges followed by selective elution and quantification using graphite furnace atomic absorption spectroscopy. Water samples can be delivered to a set of three cartridges using either syringes or peristaltic pumps. Species distribution is stable at this point, and the cartridges can be transported to the laboratory for elution and quantitative analysis. A set of ten replicate spiked samples of each compound, having concentrations between 1 and 60 μg/L, were analyzed. Arsenic recoveries ranged from 78% to 112% and relative standard deviations were generally below 10%. Resolution between species was shown to be outstanding, with the only limitation being that the capacity for As (V) was limited to approximately 50 μg/L. This could be easily remedied by changes in either cartridge design, or the extraction procedure. Recoveries were similar for two spiked hard groundwater samples indicating that dissolved minerals are not likely to be problematic. These results suggest that this methodology can be use for analysis of the four primary arsenic species of concern in
DC-based magnetic field controller
Kotter, D.K.; Rankin, R.A.; Morgan, J.P.
1994-05-31
A magnetic field controller is described for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a Hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage. 1 fig.
DC-based magnetic field controller
Kotter, Dale K.; Rankin, Richard A.; Morgan, John P,.
1994-01-01
A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.
NASA Astrophysics Data System (ADS)
Meng, Qing-Xin; Pan, He-Ping; Luo, Miao
2015-12-01
We conducted a study on the numerical calculation and response analysis of a transient electromagnetic field generated by a ground source in geological media. One solution method, the traditional discrete image method, involves complex operation, and its digital filtering algorithm requires a large number of calculations. To solve these problems, we proposed an improved discrete image method, where the following are realized: the real number of the electromagnetic field solution based on the Gaver-Stehfest algorithm for approximate inversion, the exponential approximation of the objective kernel function using the Prony method, the transient electromagnetic field according to discrete image theory, and closed-form solution of the approximate coefficients. To verify the method, we tentatively calculated the transient electromagnetic field in a homogeneous model and compared it with the results obtained from the Hankel transform digital filtering method. The results show that the method has considerable accuracy and good applicability. We then used this method to calculate the transient electromagnetic field generated by a ground magnetic dipole source in a typical geoelectric model and analyzed the horizontal component response of the induced magnetic field obtained from the "ground excitation-stratum measurement" method. We reached the conclusion that the horizontal component response of a transient field is related to the geoelectric structure, observation time, spatial location, and others. The horizontal component response of the induced magnetic field reflects the eddy current field distribution and its vertical gradient variation. During the detection of abnormal objects, positions with a zero or comparatively large offset were selected for the drillhole measurements or a comparatively long observation delay was adopted to reduce the influence of the ambient field on the survey results. The discrete image method and forward calculation results in this paper
Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces.
Goldschmidt, Benjamin S; Rudy, Anna M; Nowak, Charissa A; Tsay, Yowting; Whiteside, Paul J D; Hunt, Heather K
2016-01-01
Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. Optical property evaluation of thin films and the surfaces of bulk materials is an important step in understanding new optical material systems and their applications. The method presented can estimate thickness, refractive index, and use absorptive properties of materials for detection. This metrology system uses evanescent field-based photoacoustics (EFPA), a field of research based upon the interaction of an evanescent field with the photoacoustic effect. This interaction and its resulting family of techniques allow the technique to probe optical properties within a few hundred nanometers of the sample surface. This optical near field allows for the highly accurate estimation of material properties on the same scale as the field itself such as refractive index and film thickness. With the use of EFPA and its sub techniques such as total internal reflection photoacoustic spectroscopy (TIRPAS) and optical tunneling photoacoustic spectroscopy (OTPAS), it is possible to evaluate a material at the nanoscale in a consolidated instrument without the need for many instruments and experiments that may be cost prohibitive. PMID:27500652
Statistical Downscaling Based on Spartan Spatial Random Fields
NASA Astrophysics Data System (ADS)
Hristopulos, Dionissios
2010-05-01
Stochastic methods of space-time interpolation and conditional simulation have been used in statistical downscaling approaches to increase the resolution of measured fields. One of the popular interpolation methods in geostatistics is kriging, also known as optimal interpolation in data assimilation. Kriging is a stochastic, linear interpolator which incorporates time/space variability by means of the variogram function. However, estimation of the variogram from data involves various assumptions and simplifications. At the same time, the high numerical complexity of kriging makes it difficult to use for very large data sets. We present a different approach based on the so-called Spartan Spatial Random Fields (SSRFs). SSRFs were motivated from classical field theories of statistical physics [1]. The SSRFs provide a different approach of parametrizing spatial dependence based on 'effective interactions,' which can be formulated based on general statistical principles or even incorporate physical constraints. This framework leads to a broad family of covariance functions [2], and it provides new perspectives in covariance parameter estimation and interpolation [3]. A significant advantage offered by SSRFs is reduced numerical complexity, which can lead to much faster codes for spatial interpolation and conditional simulation. In addition, on grids composed of rectangular cells, the SSRF representation leads to an explicit expression for the precision matrix (the inverse covariance). Therefore SSRFs could provide useful models of error covariance for data assimilation methods. We use simulated and real data to demonstrate SSRF properties and downscaled fields. keywords: interpolation, conditional simulation, precision matrix References [1] Hristopulos, D.T., 2003. Spartan Gibbs random field models for geostatistical applications, SIAM Journal in Scientific Computation, 24, 2125-2162. [2] Hristopulos, D.T., Elogne, S. N. 2007. Analytic properties and covariance
Interferometric methods for mapping static electric and magnetic fields
NASA Astrophysics Data System (ADS)
Pozzi, Giulio; Beleggia, Marco; Kasama, Takeshi; Dunin-Borkowski, Rafal E.
2014-02-01
The mapping of static electric and magnetic fields using electron probes with a resolution and sensitivity that are sufficient to reveal nanoscale features in materials requires the use of phase-sensitive methods such as the shadow technique, coherent Foucault imaging and the Transport of Intensity Equation. Among these approaches, image-plane off-axis electron holography in the transmission electron microscope has acquired a prominent role thanks to its quantitative capabilities and broad range of applicability. After a brief overview of the main ideas and methods behind field mapping, we focus on theoretical models that form the basis of the quantitative interpretation of electron holographic data. We review the application of electron holography to a variety of samples (including electric fields associated with p-n junctions in semiconductors, quantized magnetic flux in superconductors and magnetization topographies in nanoparticles and other magnetic materials) and electron-optical geometries (including multiple biprism, amplitude and mixed-type set-ups). We conclude by highlighting the emerging perspectives of (i) three-dimensional field mapping using electron holographic tomography and (ii) the model-independent determination of the locations and magnitudes of field sources (electric charges and magnetic dipoles) directly from electron holographic data.
Multiresolution and Explicit Methods for Vector Field Analysis and Visualization
NASA Technical Reports Server (NTRS)
Nielson, Gregory M.
1997-01-01
This is a request for a second renewal (3d year of funding) of a research project on the topic of multiresolution and explicit methods for vector field analysis and visualization. In this report, we describe the progress made on this research project during the second year and give a statement of the planned research for the third year. There are two aspects to this research project. The first is concerned with the development of techniques for computing tangent curves for use in visualizing flow fields. The second aspect of the research project is concerned with the development of multiresolution methods for curvilinear grids and their use as tools for visualization, analysis and archiving of flow data. We report on our work on the development of numerical methods for tangent curve computation first.
Fast Field Calibration of MIMU Based on the Powell Algorithm
Ma, Lin; Chen, Wanwan; Li, Bin; You, Zheng; Chen, Zhigang
2014-01-01
The calibration of micro inertial measurement units is important in ensuring the precision of navigation systems, which are equipped with microelectromechanical system sensors that suffer from various errors. However, traditional calibration methods cannot meet the demand for fast field calibration. This paper presents a fast field calibration method based on the Powell algorithm. As the key points of this calibration, the norm of the accelerometer measurement vector is equal to the gravity magnitude, and the norm of the gyro measurement vector is equal to the rotational velocity inputs. To resolve the error parameters by judging the convergence of the nonlinear equations, the Powell algorithm is applied by establishing a mathematical error model of the novel calibration. All parameters can then be obtained in this manner. A comparison of the proposed method with the traditional calibration method through navigation tests shows the classic performance of the proposed calibration method. The proposed calibration method also saves more time compared with the traditional calibration method. PMID:25177801
Evolutionary Based Techniques for Fault Tolerant Field Programmable Gate Arrays
NASA Technical Reports Server (NTRS)
Larchev, Gregory V.; Lohn, Jason D.
2006-01-01
The use of SRAM-based Field Programmable Gate Arrays (FPGAs) is becoming more and more prevalent in space applications. Commercial-grade FPGAs are potentially susceptible to permanently debilitating Single-Event Latchups (SELs). Repair methods based on Evolutionary Algorithms may be applied to FPGA circuits to enable successful fault recovery. This paper presents the experimental results of applying such methods to repair four commonly used circuits (quadrature decoder, 3-by-3-bit multiplier, 3-by-3-bit adder, 440-7 decoder) into which a number of simulated faults have been introduced. The results suggest that evolutionary repair techniques can improve the process of fault recovery when used instead of or as a supplement to Triple Modular Redundancy (TMR), which is currently the predominant method for mitigating FPGA faults.
Real-Time Tracking Method for a Magnetic Target Using Total Geomagnetic Field Intensity
NASA Astrophysics Data System (ADS)
Fan, Liming; Kang, Chong; Zhang, Xiaojun; Wan, Shengwei
2016-06-01
We propose an efficient and effective method for real-time tracking a long-range magnetic target using total geomagnetic field intensity. This method is based on a scalar magnetometer sensor array and an improved particle swarm optimization algorithm. Due to the effect of the geomagnetic field variations, the detection distance range of the method based on the gradient tensor is short. To increase the detection range, the geomagnetic field variations must be eliminated in the method. In this paper, the geomagnetic quasi-gradient calculated from total geomagnetic field intensity in the sensor array is used. We design a sensor array with five magnetometers and use the geomagnetic quasi-gradient to eliminate the geomagnetic field variations. The improved particle swarm optimization (IPSO) algorithm, which minimizes the errors of total geomagnetic field values between measurements and calculations, is applied in this real-time tracking method to track a long-range magnetic target position. The detailed principle of the method and the steps of the IPSO algorithm are described in detail. The method is validated with a numerical simulation. The results show that the average relative error of position is less than 2 % and the execution time is less than 1.5 s.
Extending methods: using Bourdieu's field analysis to further investigate taste
NASA Astrophysics Data System (ADS)
Schindel Dimick, Alexandra
2015-06-01
In this commentary on Per Anderhag, Per-Olof Wickman and Karim Hamza's article Signs of taste for science, I consider how their study is situated within the concern for the role of science education in the social and cultural production of inequality. Their article provides a finely detailed methodology for analyzing the constitution of taste within science education classrooms. Nevertheless, because the authors' socially situated methodology draws upon Bourdieu's theories, it seems equally important to extend these methods to consider how and why students make particular distinctions within a relational context—a key aspect of Bourdieu's theory of cultural production. By situating the constitution of taste within Bourdieu's field analysis, researchers can explore the ways in which students' tastes and social positionings are established and transformed through time, space, place, and their ability to navigate the field. I describe the process of field analysis in relation to the authors' paper and suggest that combining the authors' methods with a field analysis can provide a strong methodological and analytical framework in which theory and methods combine to create a detailed understanding of students' interest in relation to their context.
Subjective perceptual methods for comparing backpacks in the field.
Legg, S J; Barr A, A; Hedderley, D I
2003-07-15
Subjective perceptual methods have provided useful information in the laboratory about small differences in backpack design when physiological and biomechanical comparisons are ineffective, but have never been used in the field. This study therefore evaluated, in a controlled field trial with 10 male participants, the suitability of quantitative and qualitative subjective perceptual approaches to distinguish between subtle design differences in two backpacks, each loaded to 15 kg. In addition, initial quantitative subjective impressions about the two backpacks during a 15 min simulated 'in-shop' trial were compared with post-field trial backpack preference. In the simulated 'in-shop' trial the participants 'tried out' the backpack in a manner that was very similar to the way that they would normally try out a backpack as if they were considering buying one in an 'outdoor' shop. It included donning and doffing the pack several times and walking around the room wearing the backpack. In the controlled field trial, participants carried the two backpacks for approximately 15 min around a 1313 m hilly outdoor track at a self-selected walking pace which elicited a moderate exercise intensity. Seven participants preferred backpack A. Three preferred backpack B. The qualitative approach, which required participants to provide free-format written responses to semi-structured open-ended questions immediately after the field trial, successfully identified specific reasons underlying participants' preferences. The main reasons for preferring backpack A were better balance, weight distribution, stability up and down hill and over obstacles, fewer pressure points on their back and easier strap location and adjustment. The quantitative approach, which involved participants responding to written post-field trial questions on visual analogue or category ratio rating scales, was generally unsuccessful in distinguishing between backpacks. Thus, qualitative subjective perceptual
Ray, J.; Lee, J.; Yadav, V.; Lefantzi, S.; Michalak, A. M.; van Bloemen Waanders, B.
2014-08-20
We present a sparse reconstruction scheme that can also be used to ensure non-negativity when fitting wavelet-based random field models to limited observations in non-rectangular geometries. The method is relevant when multiresolution fields are estimated using linear inverse problems. Examples include the estimation of emission fields for many anthropogenic pollutants using atmospheric inversion or hydraulic conductivity in aquifers from flow measurements. The scheme is based on three new developments. Firstly, we extend an existing sparse reconstruction method, Stagewise Orthogonal Matching Pursuit (StOMP), to incorporate prior information on the target field. Secondly, we develop an iterative method that uses StOMP tomore » impose non-negativity on the estimated field. Finally, we devise a method, based on compressive sensing, to limit the estimated field within an irregularly shaped domain. We demonstrate the method on the estimation of fossil-fuel CO2 (ffCO2) emissions in the lower 48 states of the US. The application uses a recently developed multiresolution random field model and synthetic observations of ffCO2 concentrations from a limited set of measurement sites. We find that our method for limiting the estimated field within an irregularly shaped region is about a factor of 10 faster than conventional approaches. It also reduces the overall computational cost by a factor of two. Further, the sparse reconstruction scheme imposes non-negativity without introducing strong nonlinearities, such as those introduced by employing log-transformed fields, and thus reaps the benefits of simplicity and computational speed that are characteristic of linear inverse problems.« less
Field methods to measure surface displacement and strain with the Video Image Correlation method
NASA Technical Reports Server (NTRS)
Maddux, Gary A.; Horton, Charles M.; Mcneill, Stephen R.; Lansing, Matthew D.
1994-01-01
The objective of this project was to develop methods and application procedures to measure displacement and strain fields during the structural testing of aerospace components using paint speckle in conjunction with the Video Image Correlation (VIC) system.
An Efficient Method for Far-field Tsunami Forecasting
NASA Astrophysics Data System (ADS)
Hossen, M. J.; Cummins, P. R.; Dettmer, J.; Baba, T.
2015-12-01
We have developed a hybrid method to forecast far-field tsunamis by combining traditional, least-squares inversion for initial sea surface displacement (LSQ) and time reverse imaging (TRI). This method has the same source representation as LSQ, which involves dividing the source region into a grid of "point" sources. For each of these, a tsunami Green's function (GF) is computed using a basis function for sea surface displacement whose support is concentrated near the grid point. Instead of solving the linear inverse problem for initial sea surface displacement using regularized least-squares, we apply the TRI method to estimate initial sea surface displacement at each source grid point by convolving GFs with time-reversed observed waveforms recorded near the source region. This tsunami-source estimate is then used to forecast tsunami waveforms at greater distance. We apply this method to the 2011 Tohoku, Japan tsunami because of the availability of an extensive set of high-quality tsunami waveform recordings. The results show that the method can predict tsunami waveforms having good agreement with observed waveforms at near-field stations not part of the source estimation, and excellent agreement with far-field waveforms. The spatial distribution of cumulative sea surface displacement agrees well with other models obtained in more sophisticated inversions, but the temporal resolution of this method does not resolve source kinematics. The method has potential for application in tsunami warning systems, as it is computationally efficient and can be applied to estimate the initial source model by applying precomputed Green's functions in order to provide more accurate and realistic tsunami predictions.
New method of asymmetric flow field measurement in hypersonic shock tunnel.
Yan, D P; He, A Z; Ni, X W
1991-03-01
In this paper a method of large aperture (?500 mm) high sensitivity moire deflectometry is used to obtain multidirectional deflectograms of the asymmetric flow field in hypersonic (M = 10.29) shock tunnel. At the same time, a 3-D reconstructive method of the asymmetric flow field is presented which is based on the integration of the moire deflective angle and the double-cubic many-knot interpolating splines; it is used to calculate the 3-D density distribution of the asymmetric flow field.
Magnetic space-based field measurements
NASA Technical Reports Server (NTRS)
Langel, R. A.
1981-01-01
Because the near Earth magnetic field is a complex combination of fields from outside the Earth of fields from its core and of fields from its crust, measurements from space prove to be the only practical way to obtain timely, global surveys. Due to difficulty in making accurate vector measurements, early satellites such as Sputnik and Vanguard measured only the magnitude survey. The attitude accuracy was 20 arc sec. Both the Earth's core fields and the fields arising from its crust were mapped from satellite data. The standard model of the core consists of a scalar potential represented by a spherical harmonics series. Models of the crustal field are relatively new. Mathematical representation is achieved in localized areas by arrays of dipoles appropriately located in the Earth's crust. Measurements of the Earth's field are used in navigation, to map charged particles in the magnetosphere, to study fluid properties in the Earth's core, to infer conductivity of the upper mantels, and to delineate regional scale geological features.
A self-consistent field method for galactic dynamics
NASA Technical Reports Server (NTRS)
Hernquist, Lars; Ostriker, Jeremiah P.
1992-01-01
The present study describes an algorithm for evolving collisionless stellar systems in order to investigate the evolution of systems with density profiles like the R exp 1/4 law, using only a few terms in the expansions. A good fit is obtained for a truncated isothermal distribution, which renders the method appropriate for galaxies with flat rotation curves. Calculations employing N of about 10 exp 6-7 are straightforward on existing supercomputers, making possible simulations having significantly smoother fields than with direct methods such as tree-codes. Orbits are found in a given static or time-dependent gravitational field; the potential, phi(r, t) is revised from the resultant density, rho(r, t). Possible scientific uses of this technique are discussed, including tidal perturbations of dwarf galaxies, the adiabatic growth of central masses in spheroidal galaxies, instabilities in realistic galaxy models, and secular processes in galactic evolution.
A Method for Evaluating Volt-VAR Optimization Field Demonstrations
Schneider, Kevin P.; Weaver, T. F.
2014-08-31
In a regulated business environment a utility must be able to validate that deployed technologies provide quantifiable benefits to the end-use customers. For traditional technologies there are well established procedures for determining what benefits will be derived from the deployment. But for many emerging technologies procedures for determining benefits are less clear and completely absent in some cases. Volt-VAR Optimization is a technology that is being deployed across the nation, but there are still numerous discussions about potential benefits and how they are achieved. This paper will present a method for the evaluation, and quantification of benefits, for field deployments of Volt-VAR Optimization technologies. In addition to the basic methodology, the paper will present a summary of results, and observations, from two separate Volt-VAR Optimization field evaluations using the proposed method.
Method for imaging with low frequency electromagnetic fields
Lee, K.H.; Xie, G.Q.
1994-12-13
A method is described for imaging with low frequency electromagnetic fields, and for interpreting the electromagnetic data using ray tomography, in order to determine the earth conductivity with high accuracy and resolution. The imaging method includes the steps of placing one or more transmitters, at various positions in a plurality of transmitter holes, and placing a plurality of receivers in a plurality of receiver holes. The transmitters generate electromagnetic signals which diffuse through a medium, such as earth, toward the receivers. The measured diffusion field data H is then transformed into wavefield data U. The travel times corresponding to the wavefield data U, are then obtained, by charting the wavefield data U, using a different regularization parameter [alpha] for each transform. The desired property of the medium, such as conductivity, is then derived from the velocity, which in turn is constructed from the wavefield data U using ray tomography. 13 figures.
Method for imaging with low frequency electromagnetic fields
Lee, Ki H.; Xie, Gan Q.
1994-01-01
A method for imaging with low frequency electromagnetic fields, and for interpreting the electromagnetic data using ray tomography, in order to determine the earth conductivity with high accuracy and resolution. The imaging method includes the steps of placing one or more transmitters, at various positions in a plurality of transmitter holes, and placing a plurality of receivers in a plurality of receiver holes. The transmitters generate electromagnetic signals which diffuse through a medium, such as earth, toward the receivers. The measured diffusion field data H is then transformed into wavefield data U. The traveltimes corresponding to the wavefield data U, are then obtained, by charting the wavefield data U, using a different regularization parameter .alpha. for each transform. The desired property of the medium, such as conductivity, is then derived from the velocity, which in turn is constructed from the wavefield data U using ray tomography.
The reduced basis method for the electric field integral equation
Fares, M.; Hesthaven, J.S.; Maday, Y.; Stamm, B.
2011-06-20
We introduce the reduced basis method (RBM) as an efficient tool for parametrized scattering problems in computational electromagnetics for problems where field solutions are computed using a standard Boundary Element Method (BEM) for the parametrized electric field integral equation (EFIE). This combination enables an algorithmic cooperation which results in a two step procedure. The first step consists of a computationally intense assembling of the reduced basis, that needs to be effected only once. In the second step, we compute output functionals of the solution, such as the Radar Cross Section (RCS), independently of the dimension of the discretization space, for many different parameter values in a many-query context at very little cost. Parameters include the wavenumber, the angle of the incident plane wave and its polarization.
Field's stain--a rapid staining method for Acanthamoeba spp.
Pirehma, M; Suresh, K; Sivanandam, S; Anuar, A K; Ramakrishnan, K; Kumar, G S
1999-10-01
Acanthamoeba sp. is a free-living amoeba known to cause chronic central nervous system infection or eye infection in humans. Many cases remain undetected for want of a good detection system. We report for the first time a rapid staining method to facilitate the identification of Acanthamoeba sp. using the modified Field's staining technique. A. castellanii, which was used in the present experiment, is maintained in our laboratory in mycological peptone medium (Gibco). The cultures were pooled together and smears were made on glass slides for staining purposes. Different types of stains such as Field's stain, modified Field's stain, Wright's stain, Giemsa stain, Ziehl-Neelsen stain, and trichrome stain were used to determine the best stain for the identification of this amoeba. The concentration of various stains and the duration of staining were varied to provide the best color and contrast for each stain. Acanthamoeba was also obtained from the brain of experimentally infected mice and was stained with various stains as mentioned above to determine the best stain for use in identifying the presence of this parasite in experimentally infected animals. The modified Field's stain gives a very good color contrast as compared with other stains. Furthermore, it takes only 20 s to be carried out using the least number of reagents, making it suitable for both laboratory and field use.
Tattoli, F.; Casavola, C.; Pierron, F.; Rotinat, R.; Pappalettere, C.
2011-01-17
One of the main problems in welding is the microstructural transformation within the area affected by the thermal history. The resulting heterogeneous microstructure within the weld nugget and the heat affected zones is often associated with changes in local material properties. The present work deals with the identification of material parameters governing the elasto--plastic behaviour of the fused and heat affected zones as well as the base material for titanium hybrid welded joints (Ti6Al4V alloy). The material parameters are identified from heterogeneous strain fields with the Virtual Fields Method. This method is based on a relevant use of the principle of virtual work and it has been shown to be useful and much less time consuming than classical finite element model updating approaches applied to similar problems. The paper will present results and discuss the problem of selection of the weld zones for the identification.
Work function measurements by the field emission retarding potential method.
NASA Technical Reports Server (NTRS)
Strayer, R. W.; Mackie, W.; Swanson, L. W.
1973-01-01
Description of the theoretical foundation of the field electron retarding potential method, and review of its experimental application to the measurement of single crystal face work functions. The results obtained from several substrates are discussed. An interesting and useful fallout from the experimental approach described is the ability to accurately measure the elastic and inelastic reflection coefficient for impinging electrons to near zero-volt energy.
Lidar Tracking of Multiple Fluorescent Tracers: Method and Field Test
NASA Technical Reports Server (NTRS)
Eberhard, Wynn L.; Willis, Ron J.
1992-01-01
Past research and applications have demonstrated the advantages and usefulness of lidar detection of a single fluorescent tracer to track air motions. Earlier researchers performed an analytical study that showed good potential for lidar discrimination and tracking of two or three different fluorescent tracers at the same time. The present paper summarizes the multiple fluorescent tracer method, discusses its expected advantages and problems, and describes our field test of this new technique.
[Methods of dosimetry in evaluation of electromagnetic fields' biological action].
Rubtsova, N B; Perov, S Iu
2012-01-01
Theoretical and experimental dosimetry can be used for adequate evaluation of the effects of radiofrequency electromagnetic fields. In view of the tough electromagnetic environment in aircraft, pilots' safety is of particular topicality. The dosimetric evaluation is made from the quantitative characteristics of the EMF interaction with bio-objects depending on EM energy absorption in a unit of tissue volume or mass calculated as a specific absorbed rate (SAR) and measured in W/kg. Theoretical dosimetry employs a number of computational methods to determine EM energy, as well as the augmented method of boundary conditions, iterative augmented method of boundary conditions, moments method, generalized multipolar method, finite-element method, time domain finite-difference method, and hybrid methods combining several decision plans modeling the design philosophy of navigation, radiolocation and human systems. Because of difficulties with the experimental SAR estimate, theoretical dosimetry is regarded as the first step in analysis of the in-aircraft conditions of exposure and possible bio-effects.
Performance of FFT methods in local gravity field modelling
NASA Technical Reports Server (NTRS)
Forsberg, Rene; Solheim, Dag
1989-01-01
Fast Fourier transform (FFT) methods provide a fast and efficient means of processing large amounts of gravity or geoid data in local gravity field modelling. The FFT methods, however, has a number of theoretical and practical limitations, especially the use of flat-earth approximation, and the requirements for gridded data. In spite of this the method often yields excellent results in practice when compared to other more rigorous (and computationally expensive) methods, such as least-squares collocation. The good performance of the FFT methods illustrate that the theoretical approximations are offset by the capability of taking into account more data in larger areas, especially important for geoid predictions. For best results good data gridding algorithms are essential. In practice truncated collocation approaches may be used. For large areas at high latitudes the gridding must be done using suitable map projections such as UTM, to avoid trivial errors caused by the meridian convergence. The FFT methods are compared to ground truth data in New Mexico (xi, eta from delta g), Scandinavia (N from delta g, the geoid fits to 15 cm over 2000 km), and areas of the Atlantic (delta g from satellite altimetry using Wiener filtering). In all cases the FFT methods yields results comparable or superior to other methods.
NASA Astrophysics Data System (ADS)
Boblest, S.; Meyer, D.; Wunner, G.
2014-11-01
We present a quantum Monte Carlo application for the computation of energy eigenvalues for atoms and ions in strong magnetic fields. The required guiding wave functions are obtained with the Hartree-Fock-Roothaan code described in the accompanying publication (Schimeczek and Wunner, 2014). Our method yields highly accurate results for the binding energies of symmetry subspace ground states and at the same time provides a means for quantifying the quality of the results obtained with the above-mentioned Hartree-Fock-Roothaan method. Catalogue identifier: AETV_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETV_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 72 284 No. of bytes in distributed program, including test data, etc.: 604 948 Distribution format: tar.gz Programming language: C++. Computer: Cluster of 1-˜500 HP Compaq dc5750. Operating system: Linux. Has the code been vectorized or parallelized?: Yes. Code includes MPI directives. RAM: 500 MB per node Classification: 2.1. External routines: Boost::Serialization, Boost::MPI, LAPACK BLAS Nature of problem: Quantitative modelings of features observed in the X-ray spectra of isolated neutron stars are hampered by the lack of sufficiently large and accurate databases for atoms and ions up to the last fusion product iron, at high magnetic field strengths. The predominant amount of line data in the literature has been calculated with Hartree-Fock methods, which are intrinsically restricted in precision. Our code is intended to provide a powerful tool for calculating very accurate energy values from, and thereby improving the quality of, existing Hartree-Fock results. Solution method: The Fixed-phase quantum Monte Carlo method is used in combination with guiding functions obtained in Hartree
ALTERNATIVE FIELD METHODS TO TREAT MERCURY IN SOIL
Ernest F. Stine Jr; Steven T. Downey
2002-08-14
U.S. Department of Energy (DOE) used large quantities of mercury in the uranium separating process from the 1950s until the late 1980s in support of national defense. Some of this mercury, as well as other hazardous metals and radionuclides, found its way into, and under, several buildings, soil and subsurface soils and into some of the surface waters. Several of these areas may pose potential health or environmental risks and must be dealt with under current environmental regulations. DOE's National Energy Technology Laboratory (NETL) awarded a contract ''Alternative Field Methods to Treat Mercury in Soil'' to IT Group, Knoxville TN (IT) and its subcontractor NFS, Erwin, TN to identify remedial methods to clean up mercury-contaminated high-clay content soils using proven treatment chemistries. The sites of interest were the Y-12 National Security Complex located in Oak Ridge, Tennessee, the David Witherspoon properties located in Knoxville, Tennessee, and at other similarly contaminated sites. The primary laboratory-scale contract objectives were (1) to safely retrieve and test samples of contaminated soil in an approved laboratory and (2) to determine an acceptable treatment method to ensure that the mercury does not leach from the soil above regulatory levels. The leaching requirements were to meet the TC (0.2 mg/l) and UTS (0.025 mg/l) TCLP criteria. In-situ treatments were preferred to control potential mercury vapors emissions and liquid mercury spills associated with ex-situ treatments. All laboratory work was conducted in IT's and NFS laboratories. Mercury contaminated nonradioactive soil from under the Alpha 2 building in the Y-12 complex was used. This soils contained insufficient levels of leachable mercury and resulted in TCLP mercury concentrations that were similar to the applicable LDR limits. The soil was spiked at multiple levels with metallic (up to 6000 mg/l) and soluble mercury compounds (up to 500 mg/kg) to simulate expected ranges of mercury
DOM Based XSS Detecting Method Based on Phantomjs
NASA Astrophysics Data System (ADS)
Dong, Ri-Zhan; Ling, Jie; Liu, Yi
Because malicious code does not appear in html source code, DOM based XSS cannot be detected by traditional methods. By analyzing the causes of DOM based XSS, this paper proposes a detection method of DOM based XSS based on phantomjs. This paper uses function hijacking to detect dangerous operation and achieves a prototype system. Comparing with existing tools shows that the system improves the detection rate and the method is effective to detect DOM based XSS.
Methods for classification of agricultural fields in aerial sequences: a comparative study
NASA Astrophysics Data System (ADS)
Houkes, Zweitze; Chen, Haijun; Blacquiere, Jan-Friso
1998-12-01
A comparative study of a selection of classification methods for agricultural fields in sequences of aerial images is presented. The image sequences are acquired by an RGB-CCD video camera which is assumed to be on board of an airplane, moving linear over the scene. The objects in the scenes being considered are agricultural fields. The classes of agricultural fields to be distinguished are determined by the type of crop, e.g. potatoes, sugar beet, wheat, etc. In order to recognize and classify these fields obtained from the aerial sequences of images, a common approach is in the use of surface texture. Textural features are extracted from the images to effectively characterize the vegetation. Methods based on Circular Symmetric Auto-Regression, Co-Occurrence Matrix and Local Binary Patterns are selected for the comparative study. The experiments are carried out with image sequences taken from a scaled model of a landscape and a selection from the Brodatz set. A few training images are used to set up the model bases for the three methods. The methods are tested using the same regions from other images of the sequence, and other sequences of images of similar fields. Comparison fa the methods is based on the confusion matrix. Sensitivity to variations in flight direction, variations in altitude and luminance conditions are being considered.
DNA-based methods of geochemical prospecting
Ashby, Matthew
2011-12-06
The present invention relates to methods for performing surveys of the genetic diversity of a population. The invention also relates to methods for performing genetic analyses of a population. The invention further relates to methods for the creation of databases comprising the survey information and the databases created by these methods. The invention also relates to methods for analyzing the information to correlate the presence of nucleic acid markers with desired parameters in a sample. These methods have application in the fields of geochemical exploration, agriculture, bioremediation, environmental analysis, clinical microbiology, forensic science and medicine.
Modeling enzymatic transition states by force field methods
NASA Astrophysics Data System (ADS)
Hansen, M. B.; Jensen, H. J. A.; Jensen, F.
The SEAM method, which models a transition structure as a minimum on the seam of two diabatic surfaces represented by force field functions, has been used to generate 20 transition structures for the decarboxylation of orotidine by the orotidine-5prime-monophosphate decarboxylase enzyme. The dependence of the TS geometry on the flexibility of the system has been probed by fixing layers of atoms around the active site and using increasingly larger nonbonded cutoffs. The variability over the 20 structures is found to decrease as the system is made more flexible. Relative energies have been calculated by various electronic structure methods, where part of the enzyme is represented by a force field description and the effects of the solvent are represented by a continuum model. The relative energies vary by several hundreds of kJ/mol between the transition structures, and tests showed that a large part of this variation is due to changes in the enzyme structure at distances more than 5 Å from the active site. There are significant differences between the results obtained by pure quantum methods and those from mixed quantum and molecular mechanics methods.
Vision Sensor-Based Road Detection for Field Robot Navigation
Lu, Keyu; Li, Jian; An, Xiangjing; He, Hangen
2015-01-01
Road detection is an essential component of field robot navigation systems. Vision sensors play an important role in road detection for their great potential in environmental perception. In this paper, we propose a hierarchical vision sensor-based method for robust road detection in challenging road scenes. More specifically, for a given road image captured by an on-board vision sensor, we introduce a multiple population genetic algorithm (MPGA)-based approach for efficient road vanishing point detection. Superpixel-level seeds are then selected in an unsupervised way using a clustering strategy. Then, according to the GrowCut framework, the seeds proliferate and iteratively try to occupy their neighbors. After convergence, the initial road segment is obtained. Finally, in order to achieve a globally-consistent road segment, the initial road segment is refined using the conditional random field (CRF) framework, which integrates high-level information into road detection. We perform several experiments to evaluate the common performance, scale sensitivity and noise sensitivity of the proposed method. The experimental results demonstrate that the proposed method exhibits high robustness compared to the state of the art. PMID:26610514
Vision Sensor-Based Road Detection for Field Robot Navigation.
Lu, Keyu; Li, Jian; An, Xiangjing; He, Hangen
2015-11-24
Road detection is an essential component of field robot navigation systems. Vision sensors play an important role in road detection for their great potential in environmental perception. In this paper, we propose a hierarchical vision sensor-based method for robust road detection in challenging road scenes. More specifically, for a given road image captured by an on-board vision sensor, we introduce a multiple population genetic algorithm (MPGA)-based approach for efficient road vanishing point detection. Superpixel-level seeds are then selected in an unsupervised way using a clustering strategy. Then, according to the GrowCut framework, the seeds proliferate and iteratively try to occupy their neighbors. After convergence, the initial road segment is obtained. Finally, in order to achieve a globally-consistent road segment, the initial road segment is refined using the conditional random field (CRF) framework, which integrates high-level information into road detection. We perform several experiments to evaluate the common performance, scale sensitivity and noise sensitivity of the proposed method. The experimental results demonstrate that the proposed method exhibits high robustness compared to the state of the art.
Vision Sensor-Based Road Detection for Field Robot Navigation.
Lu, Keyu; Li, Jian; An, Xiangjing; He, Hangen
2015-01-01
Road detection is an essential component of field robot navigation systems. Vision sensors play an important role in road detection for their great potential in environmental perception. In this paper, we propose a hierarchical vision sensor-based method for robust road detection in challenging road scenes. More specifically, for a given road image captured by an on-board vision sensor, we introduce a multiple population genetic algorithm (MPGA)-based approach for efficient road vanishing point detection. Superpixel-level seeds are then selected in an unsupervised way using a clustering strategy. Then, according to the GrowCut framework, the seeds proliferate and iteratively try to occupy their neighbors. After convergence, the initial road segment is obtained. Finally, in order to achieve a globally-consistent road segment, the initial road segment is refined using the conditional random field (CRF) framework, which integrates high-level information into road detection. We perform several experiments to evaluate the common performance, scale sensitivity and noise sensitivity of the proposed method. The experimental results demonstrate that the proposed method exhibits high robustness compared to the state of the art. PMID:26610514
Lattice-based flow field modeling.
Wei, Xiaoming; Zhao, Ye; Fan, Zhe; Li, Wei; Qiu, Feng; Yoakum-Stover, Suzanne; Kaufman, Arie E
2004-01-01
We present an approach for simulating the natural dynamics that emerge from the interaction between a flow field and immersed objects. We model the flow field using the Lattice Boltzmann Model (LBM) with boundary conditions appropriate for moving objects and accelerate the computation on commodity graphics hardware (GPU) to achieve real-time performance. The boundary conditions mediate the exchange of momentum between the flow field and the moving objects resulting in forces exerted by the flow on the objects as well as the back-coupling on the flow. We demonstrate our approach using soap bubbles and a feather. The soap bubbles illustrate Fresnel reflection, reveal the dynamics of the unseen flow field in which they travel, and display spherical harmonics in their undulations. Our simulation allows the user to directly interact with the flow field to influence the dynamics in real time. The free feather flutters and gyrates in response to lift and drag forces created by its motion relative to the flow. Vortices are created as the free feather falls in an otherwise quiescent flow. PMID:15527053
Camera array based light field microscopy
Lin, Xing; Wu, Jiamin; Zheng, Guoan; Dai, Qionghai
2015-01-01
This paper proposes a novel approach for high-resolution light field microscopy imaging by using a camera array. In this approach, we apply a two-stage relay system for expanding the aperture plane of the microscope into the size of an imaging lens array, and utilize a sensor array for acquiring different sub-apertures images formed by corresponding imaging lenses. By combining the rectified and synchronized images from 5 × 5 viewpoints with our prototype system, we successfully recovered color light field videos for various fast-moving microscopic specimens with a spatial resolution of 0.79 megapixels at 30 frames per second, corresponding to an unprecedented data throughput of 562.5 MB/s for light field microscopy. We also demonstrated the use of the reported platform for different applications, including post-capture refocusing, phase reconstruction, 3D imaging, and optical metrology. PMID:26417490
METHOD AND APPARATUS FOR TRAPPING IONS IN A MAGNETIC FIELD
Luce, J.S.
1962-04-17
A method and apparatus are described for trapping ions within an evacuated container and within a magnetic field utilizing dissociation and/or ionization of molecular ions to form atomic ions and energetic neutral particles. The atomic ions are magnetically trapped as a result of a change of charge-to- mass ratio. The molecular ions are injected into the container and into the path of an energetic carbon arc discharge which dissociates and/or ionizes a portion of the molecular ions into atomic ions and energetic neutrals. The resulting atomic ions are trapped by the magnetic field to form a circulating beam of atomic ions, and the energetic neutrals pass out of the system and may be utilized in a particle accelerator. (AEC)
Magnetic Field Configuration Models and Reconstruction Methods: a comparative study
NASA Astrophysics Data System (ADS)
Al-haddad, Nada; Möstl, Christian; Roussev, Ilia; Nieves-Chinchilla, Teresa; Poedts, Stefaan; Hidalgo, Miguel Angel; Marubashi, Katsuhide; Savani, Neel
2012-07-01
This study aims to provide a reference to different magnetic field models and reconstruction methods. In order to understand the dissimilarities of those models and codes, we analyze 59 events from the CDAW list, using four different magnetic field models and reconstruction techniques; force- free reconstruction (Lepping et al.(1990); Lynch et al.(2003)), magnetostatic reconstruction, referred as Grad-Shafranov (Hu & Sonnerup(2001); Mostl et al.(2009)), cylinder reconstruction (Marubashi & Lepping(2007)), elliptical, non-force free (Hidalgo et al.(2002)). The resulted parameters of the reconstructions, for the 59 events are compared, statistically, as well as in more details for some cases. The differences between the reconstruction codes are discussed, and suggestions are provided as how to enhance them. Finally we look at 2 unique cases under the microscope, to provide a comprehensive idea of the different aspects of how the fitting codes work.
Magnetic field adjustment structure and method for a tapered wiggler
Halbach, Klaus
1988-03-01
An improved method and structure is disclosed for adjusting the magnetic field generated by a group of electromagnet poles spaced along the path of a charged particle beam to compensate for energy losses in the charged particles which comprises providing more than one winding on at least some of the electromagnet poles; connecting one respective winding on each of several consecutive adjacent electromagnet poles to a first power supply, and the other respective winding on the electromagnet pole to a different power supply in staggered order; and independently adjusting one power supply to independently vary the current in one winding on each electromagnet pole in a group whereby the magnetic field strength of each of a group of electromagnet poles may be changed in smaller increments.
Magnetic field adjustment structure and method for a tapered wiggler
Halbach, Klaus
1988-01-01
An improved method and structure is disclosed for adjusting the magnetic field generated by a group of electromagnet poles spaced along the path of a charged particle beam to compensate for energy losses in the charged particles which comprises providing more than one winding on at least some of the electromagnet poles; connecting one respective winding on each of several consecutive adjacent electromagnet poles to a first power supply, and the other respective winding on the electromagnet pole to a different power supply in staggered order; and independently adjusting one power supply to independently vary the current in one winding on each electromagnet pole in a group whereby the magnetic field strength of each of a group of electromagnet poles may be changed in smaller increments.
An Empirical Method for Fast Prediction of Rarefied Flow Field around a Vertical Plate
NASA Astrophysics Data System (ADS)
He, Tao; Wang, Jiang-Feng
2016-06-01
Numerical study is conducted to investigate the effects of free-stream Knudsen (Kn) number on rarefied flow field around a vertical plate employing an unstructured DSMC method, and an empirical method for fast prediction of flow-field structure at different Kn numbers in a given inflow velocity is proposed. First, the flow at a velocity 7500m/s is simulated using a perfect-gas model with free-stream Kn changing from 0.035 to 13.36. The flow-field characteristics in these cases with varying Kn numbers are analyzed and a linear-expansion phenomenon as a function of the square of Kn is discovered. An empirical method is proposed for fast flow-field prediction at different Kn based on the least-square-fitting method. Further, the effects of chemical reactions on flow field are investigated to verify the applicability of the empirical method in the real gas conditions. Three of the cases in perfect-gas flow are simulated again by introducing five-species air chemical module. The flow properties with and without chemical reactions are compared. In the end, the variation of chemical-reaction flow field as a function of Kn is analyzed and it is shown that the empirical method are also suitable when considering chemical reactions.
Reconstruction of radiating sound fields using minimum energy method.
Bader, Rolf
2010-01-01
A method for reconstructing a pressure field at the surface of a radiating body or source is presented using recording data of a microphone array. The radiation is assumed to consist of many spherical radiators, as microphone positions are present in the array. These monopoles are weighted using a parameter alpha, which broadens or narrows the overall radiation directivity as an effective and highly intuitive parameter of the radiation characteristics. A radiation matrix is built out of these weighted monopole radiators, and for different assumed values of alpha, a linear equation solver reconstructs the pressure field at the body's surface. It appears that from these many arbitrary reconstructions, the correct one minimizes the reconstruction energy. The method is tested, localizing the radiation points of a Balinese suling flute, reconstructing complex radiation from a duff frame drum, and determining the radiation directivity for the first seven modes of an Usbek tambourine. Stability in terms of measurement noise is demonstrated for the plain method, and additional highly effective algorithm is added for a noise level up to 0 dB. The stability of alpha in terms of minimal reconstruction energy is shown over the whole range of possible values for alpha. Additionally, the treatment of unwanted room reflections is discussed, still leading to satisfactory results in many cases. PMID:20058977
Iterative Methods to Solve Linear RF Fields in Hot Plasma
NASA Astrophysics Data System (ADS)
Spencer, Joseph; Svidzinski, Vladimir; Evstatiev, Evstati; Galkin, Sergei; Kim, Jin-Soo
2014-10-01
Most magnetic plasma confinement devices use radio frequency (RF) waves for current drive and/or heating. Numerical modeling of RF fields is an important part of performance analysis of such devices and a predictive tool aiding design and development of future devices. Prior attempts at this modeling have mostly used direct solvers to solve the formulated linear equations. Full wave modeling of RF fields in hot plasma with 3D nonuniformities is mostly prohibited, with memory demands of a direct solver placing a significant limitation on spatial resolution. Iterative methods can significantly increase spatial resolution. We explore the feasibility of using iterative methods in 3D full wave modeling. The linear wave equation is formulated using two approaches: for cold plasmas the local cold plasma dielectric tensor is used (resolving resonances by particle collisions), while for hot plasmas the conductivity kernel (which includes a nonlocal dielectric response) is calculated by integrating along test particle orbits. The wave equation is discretized using a finite difference approach. The initial guess is important in iterative methods, and we examine different initial guesses including the solution to the cold plasma wave equation. Work is supported by the U.S. DOE SBIR program.
C-Field Methods for Non-Equilibrium Bose Gases
NASA Astrophysics Data System (ADS)
Davis, Matthew J.; Wright, Tod M.; Blakie, P. Blair; Bradley, Ashton S.; Ballagh, Rob J.; Gardiner, Crispin W.
2013-02-01
We review c-field methods for simulating the non-equilibrium dynamics of degenerate Bose gases beyond the mean-field Gross-Pitaevskii approximation. We describe three separate approaches that utilise similar numerical methods, but have distinct regimes of validity. Systems at finite temperature can be treated with either the closed-system projected Gross-Pitaevskii equation (PGPE), or the open-system stochastic projected Gross-Pitaevskii equation (SPGPE). These are both applicable in quantum degenerate regimes in which thermal fluctuations are significant. At low or zero temperature, the truncated Wigner projected Gross Pitaevskii equation (TWPGPE) allows for the simulation of systems in which spontaneous collision processes seeded by quantum fluctuations are important. We describe the regimes of validity of each of these methods, and discuss their relationships to one another, and to other simulation techniques for the dynamics of Bose gases. The utility of the SPGPE formalism in modelling non-equilibrium Bose gases is illustrated by its application to the dynamics of spontaneous vortex formation in the growth of a Bose-Einstein condensate.
Mappings of Fields Based on Nominations.
ERIC Educational Resources Information Center
Lenk, Peter
1983-01-01
Graphical representations of nominations and citations of colleagues in seven scientific fields--information science, human systems management, future studies, general systems, topology and differential geometry, and polymer chemistry--are presented. Conomination analysis and cocitation analysis are compared as techniques to study structure of…
Ray, J.; Lee, J.; Yadav, V.; Lefantzi, S.; Michalak, A. M.; van Bloemen Waanders, B.
2015-04-29
Atmospheric inversions are frequently used to estimate fluxes of atmospheric greenhouse gases (e.g., biospheric CO2 flux fields) at Earth's surface. These inversions typically assume that flux departures from a prior model are spatially smoothly varying, which are then modeled using a multi-variate Gaussian. When the field being estimated is spatially rough, multi-variate Gaussian models are difficult to construct and a wavelet-based field model may be more suitable. Unfortunately, such models are very high dimensional and are most conveniently used when the estimation method can simultaneously perform data-driven model simplification (removal of model parameters that cannot be reliably estimated) and fitting.more » Such sparse reconstruction methods are typically not used in atmospheric inversions. In this work, we devise a sparse reconstruction method, and illustrate it in an idealized atmospheric inversion problem for the estimation of fossil fuel CO2 (ffCO2) emissions in the lower 48 states of the USA. Our new method is based on stagewise orthogonal matching pursuit (StOMP), a method used to reconstruct compressively sensed images. Our adaptations bestow three properties to the sparse reconstruction procedure which are useful in atmospheric inversions. We have modified StOMP to incorporate prior information on the emission field being estimated and to enforce non-negativity on the estimated field. Finally, though based on wavelets, our method allows for the estimation of fields in non-rectangular geometries, e.g., emission fields inside geographical and political boundaries. Our idealized inversions use a recently developed multi-resolution (i.e., wavelet-based) random field model developed for ffCO2 emissions and synthetic observations of ffCO2 concentrations from a limited set of measurement sites. We find that our method for limiting the estimated field within an irregularly shaped region is about a factor of 10 faster than conventional approaches. It also
Nondestructive acoustic electric field probe apparatus and method
Migliori, Albert
1982-01-01
The disclosure relates to a nondestructive acoustic electric field probe and its method of use. A source of acoustic pulses of arbitrary but selected shape is placed in an oil bath along with material to be tested across which a voltage is disposed and means for receiving acoustic pulses after they have passed through the material. The received pulses are compared with voltage changes across the material occurring while acoustic pulses pass through it and analysis is made thereof to determine preselected characteristics of the material.
Phase-field elasticity model based on mechanical jump conditions
NASA Astrophysics Data System (ADS)
Schneider, Daniel; Tschukin, Oleg; Choudhury, Abhik; Selzer, Michael; Böhlke, Thomas; Nestler, Britta
2015-05-01
Computational models based on the phase-field method typically operate on a mesoscopic length scale and resolve structural changes of the material and furthermore provide valuable information about microstructure and mechanical property relations. An accurate calculation of the stresses and mechanical energy at the transition region is therefore indispensable. We derive a quantitative phase-field elasticity model based on force balance and Hadamard jump conditions at the interface. Comparing the simulated stress profiles calculated with Voigt/Taylor (Annalen der Physik 274(12):573, 1889), Reuss/Sachs (Z Angew Math Mech 9:49, 1929) and the proposed model with the theoretically predicted stress fields in a plate with a round inclusion under hydrostatic tension, we show the quantitative characteristics of the model. In order to validate the elastic contribution to the driving force for phase transition, we demonstrate the absence of excess energy, calculated by Durga et al. (Model Simul Mater Sci Eng 21(5):055018, 2013), in a one-dimensional equilibrium condition of serial and parallel material chains. To validate the driving force for systems with curved transition regions, we relate simulations to the Gibbs-Thompson equilibrium condition (Johnson and Alexander, J Appl Phys 59(8):2735, 1986).
Recent methods for the determination of peroxide-based explosives.
Schulte-Ladbeck, Rasmus; Vogel, Martin; Karst, Uwe
2006-10-01
In the last few years, the need to determine peroxide-based explosives in solid samples and air samples has resulted in the development of a series of new analytical methods for triacetonetriperoxide (TATP, acetone peroxide) and hexamethylenetriperoxidediamine (HMTD). In this review, after a short introduction describing the state of the art in the field, these new analytical methods are critically discussed. Particular emphasis is placed on spectroscopic and mass spectrometric methods as well as on chromatographic techniques with selective detection schemes. The potential of these methods to analyse unknown solid samples that might contain one or more of the explosives and to analyse peroxide-based explosives in air is evaluated.
Correlation theory-based signal processing method for CMF signals
NASA Astrophysics Data System (ADS)
Shen, Yan-lin; Tu, Ya-qing
2016-06-01
Signal processing precision of Coriolis mass flowmeter (CMF) signals affects measurement accuracy of Coriolis mass flowmeters directly. To improve the measurement accuracy of CMFs, a correlation theory-based signal processing method for CMF signals is proposed, which is comprised of the correlation theory-based frequency estimation method and phase difference estimation method. Theoretical analysis shows that the proposed method eliminates the effect of non-integral period sampling signals on frequency and phase difference estimation. The results of simulations and field experiments demonstrate that the proposed method improves the anti-interference performance of frequency and phase difference estimation and has better estimation performance than the adaptive notch filter, discrete Fourier transform and autocorrelation methods in terms of frequency estimation and the data extension-based correlation, Hilbert transform, quadrature delay estimator and discrete Fourier transform methods in terms of phase difference estimation, which contributes to improving the measurement accuracy of Coriolis mass flowmeters.
NASA Astrophysics Data System (ADS)
Feng, Xueshang; Zhang, Man
2016-03-01
This paper presents a comparative study of divergence cleaning methods of magnetic field in the solar coronal three-dimensional numerical simulation. For such purpose, the diffusive method, projection method, generalized Lagrange multiplier method and constrained-transport method are used. All these methods are combined with a finite-volume scheme based on a six-component grid system in spherical coordinates. In order to see the performance between the four divergence cleaning methods, solar coronal numerical simulation for Carrington rotation 2056 has been studied. Numerical results show that the average relative divergence error is around 10^{-4.5} for the constrained-transport method, while about 10^{-3.1}- 10^{-3.6} for the other three methods. Although there exist some differences in the average relative divergence errors for the four employed methods, our tests show they can all produce basic structured solar wind.
The methods and instructions for field operations presented in this manual for surveys of non-wadeable streams and rivers were developed and tested based on 55 sample sites in the Mid-Atlantic region and 53 sites in an Oregon study during two years of pilot and demonstration proj...
B. Julia-Diaz, H. Kamano, T.-S. H. Lee, A. Matsuyama, T. Sato, N. Suzuki
2009-04-01
Within the relativistic quantum field theory, we analyze the differences between the $\\pi N$ reaction models constructed from using (1) three-dimensional reductions of Bethe-Salpeter Equation, (2) method of unitary transformation, and (3) time-ordered perturbation theory. Their relations with the approach based on the dispersion relations of S-matrix theory are dicusssed.
Global gravimetric geoid model based a new method
NASA Astrophysics Data System (ADS)
Shen, W. B.; Han, J. C.
2012-04-01
The geoid, defined as the equipotential surface nearest to the mean sea level, plays a key role in physical geodesy and unification of height datum system. In this study, we introduce a new method, which is quite different from the conventional geoid modeling methods (e.g., Stokes method, Molodensky method), to determine the global gravimetric geoid (GGG). Based on the new method, using the dada base of the external Earth gravity field model EGM2008, digital topographic model DTM2006.0 and crust density distribution model CRUST2.0, we first determined the inner geopotential field until to the depth of D, and then established a GGG model , the accuracy of which is evaluated by comparing with the observations from USA, AUS, some parts of Canada, and some parts of China. The main idea of the new method is stated as follows. Given the geopotential field (e.g. EGM2008) outside the Earth, we may determine the inner geopotential field until to the depth of D by using Newtonian integral, once the density distribution model (e.g. CRUST2.0) of a shallow layer until to the depth D is given. Then, based on the definition of the geoid (i.e. an equipotential surface nearest to the mean sea level) one may determine the GGG. This study is supported by Natural Science Foundation China (grant No.40974015; No.41174011; No.41021061; No.41128003).
Plouff, Donald
2000-01-01
Gravity observations are directly made or are obtained from other sources by the U.S. Geological Survey in order to prepare maps of the anomalous gravity field and consequently to interpret the subsurface distribution of rock densities and associated lithologic or geologic units. Observations are made in the field with gravity meters at new locations and at reoccupations of previously established gravity "stations." This report illustrates an interactively-prompted series of steps needed to convert gravity "readings" to values that are tied to established gravity datums and includes computer programs to implement those steps. Inasmuch as individual gravity readings have small variations, gravity-meter (instrument) drift may not be smoothly variable, and acommodations may be needed for ties to previously established stations, the reduction process is iterative. Decision-making by the program user is prompted by lists of best values and graphical displays. Notes about irregularities of topography, which affect the value of observed gravity but are not shown in sufficient detail on topographic maps, must be recorded in the field. This report illustrates ways to record field notes (distances, heights, and slope angles) and includes computer programs to convert field notes to gravity terrain corrections. This report includes approaches that may serve as models for other applications, for example: portrayal of system flow; style of quality control to document and validate computer applications; lack of dependence on proprietary software except source code compilation; method of file-searching with a dwindling list; interactive prompting; computer code to write directly in the PostScript (Adobe Systems Incorporated) printer language; and high-lighting the four-digit year on the first line of time-dependent data sets for assured Y2K compatibility. Computer source codes provided are written in the Fortran scientific language. In order for the programs to operate, they first
Field methods for rapidly characterizing paint waste during bridge rehabilitation.
Shu, Zhan; Axe, Lisa; Jahan, Kauser; Ramanujachary, Kandalam V
2015-09-01
For Department of Transportation (DOT) agencies, bridge rehabilitation involving paint removal results in waste that is often managed as hazardous. Hence, an approach that provides field characterization of the waste classification would be beneficial. In this study, an analysis of variables critical to the leaching process was conducted to develop a predictive tool for waste classification. This approach first involved identifying mechanistic processes that control leaching. Because steel grit is used to remove paint, elevated iron concentrations remain in the paint waste. As such, iron oxide coatings provide an important surface for metal adsorption. The diffuse layer model was invoked (logKMe=4.65 for Pb and logKMe=2.11 for Cr), where 90% of the data were captured within the 95% confidence level. Based on an understanding of mechanistic processes along with principal component analysis (PCA) of data obtained from field-portable X-ray fluorescence (FP-XRF), statistically-based models for leaching from paint waste were developed. Modeling resulted in 96% of the data falling within the 95% confidence level for Pb (R(2) 0.6-0.9, p ⩽ 0.04), Ba (R(2) 0.5-0.7, p ⩽ 0.1), and Zn (R(2) 0.6-0.7, p ⩽ 0.08). However, the regression model obtained for Cr leaching was not significant (R(2) 0.3-0.5, p ⩽ 0.75). The results of this work may assist DOT agencies with applying a predictive tool in the field that addresses the mobility of trace metals as well as disposal and management of paint waste during bridge rehabilitation.
A stabilized finite element method for the two-field and three-field Stokes eigenvalue problems
NASA Astrophysics Data System (ADS)
Türk, Önder; Boffi, Daniele; Codina, Ramon
2016-10-01
In this paper, the stabilized finite element approximation of the Stokes eigenvalue problems is considered for both the two-field (displacement-pressure) and the three-field (stress-displacement-pressure) formulations. The method presented is based on a subgrid scale concept, and depends on the approximation of the unresolvable scales of the continuous solution. In general, subgrid scale techniques consist in the addition of a residual based term to the basic Galerkin formulation. The application of a standard residual based stabilization method to a linear eigenvalue problem leads to a quadratic eigenvalue problem in discrete form which is physically inconvenient. As a distinguished feature of the present study, we take the space of the unresolved subscales orthogonal to the finite element space, which promises a remedy to the above mentioned complication. In essence, we put forward that only if the orthogonal projection is used, the residual is simplified and the use of term by term stabilization is allowed. Thus, we do not need to put the whole residual in the formulation, and the linear eigenproblem form is recovered properly. We prove that the method applied is convergent, and present the error estimates for the eigenvalues and the eigenfunctions. We report several numerical tests in order to illustrate that the theoretical results are validated.
Impulse-based methods for fluid flow
Cortez, R.
1995-05-01
A Lagrangian numerical method based on impulse variables is analyzed. A relation between impulse vectors and vortex dipoles with a prescribed dipole moment is presented. This relation is used to adapt the high-accuracy cutoff functions of vortex methods for use in impulse-based methods. A source of error in the long-time implementation of the impulse method is explained and two techniques for avoiding this error are presented. An application of impulse methods to the motion of a fluid surrounded by an elastic membrane is presented.
Field evaluation of endotoxin air sampling assay methods.
Thorne, P S; Reynolds, S J; Milton, D K; Bloebaum, P D; Zhang, X; Whitten, P; Burmeister, L F
1997-11-01
This study tested the importance of filter media, extraction and assay protocol, and bioaerosol source on the determination of endotoxin under field conditions in swine and poultry confinement buildings. Multiple simultaneous air samples were collected using glass fiber (GF) and polycarbonate (PC) filters, and these were assayed using two methods in two separate laboratories: an endpoint chromogenic Limulus amebocyte lysate (LAL) assay (QCL) performed in water and a kinetic chromogenic LAL assay (KQCL) performed in buffer with resistant-parallel line estimation analysis (KLARE). In addition, two aqueous filter extraction methods were compared in the QCL assay: 120 min extraction at 22 degrees C with vigorous shaking and 30 min extraction at 68 degrees C with gentle rocking. These extraction methods yielded endotoxin activities that were not significantly different and were very highly correlated. Reproducibility of endotoxin determinations from duplicate air sampling filters was very high (Cronbach alpha all > 0.94). When analyzed by the QCL method GF filters yielded significantly higher endotoxin activity than PC filters. QCL and KLARE methods gave similar estimates for endotoxin activity from PC filters; however, GF filters analyzed by the QCL method yielded significantly higher endotoxin activity estimates, suggesting enhancement of the QCL assay or inhibition of the KLARE asay with GF filters. Correlation between QCL-GF and QCL-PC was high (r = 0.98) while that between KLARE-GF and KLARE-PC was moderate (r = 0.68). Analysis of variance demonstrated that assay methodology, filter-type, barn-type, and interactions between assay and filter-type and between assay and barn-type were important factors influencing endotoxin exposure assessment.
Enzyme catalysis enhanced dark-field imaging as a novel immunohistochemical method.
Fan, Lin; Tian, Yanyan; Yin, Rong; Lou, Doudou; Zhang, Xizhi; Wang, Meng; Ma, Ming; Luo, Shouhua; Li, Suyi; Gu, Ning; Zhang, Yu
2016-04-28
Conventional immunohistochemistry is limited to subjective judgment based on human experience and thus it is clinically required to develop a quantitative immunohistochemical detection. 3,3'-Diaminobenzidin (DAB) aggregates, a type of staining product formed by conventional immunohistochemistry, were found to have a special optical property of dark-field imaging for the first time, and the mechanism was explored. On this basis, a novel immunohistochemical method based on dark-field imaging for detecting HER2 overexpressed in breast cancer was established, and the quantitative analysis standard and relevant software for measuring the scattering intensity was developed. In order to achieve a more sensitive detection, the HRP (horseradish peroxidase)-labeled secondary antibodies conjugated gold nanoparticles were constructed as nanoprobes to load more HRP enzymes, resulting in an enhanced DAB deposition as a dark-field label. Simultaneously, gold nanoparticles also act as a synergistically enhanced agent due to their mimicry of enzyme catalysis and dark-field scattering properties. PMID:26786242
An easy field method for estimating the abundance of culicid larval instars.
Carron, Alexandre; Duchet, Claire; Gaven, Bruno; Lagneau, Christophe
2003-12-01
A new method is proposed that avoids manual counting of mosquito larvae in order to estimate larval abundance in the field. This method is based on the visual comparison between abundance, in a standardized sampling tray (called an abacus), with 5 (abacus 5) or 10 (abacus 10) diagrammatically prepared abundance classes. Accuracy under laboratory and field conditions and individual bias have been evaluated and both abaci provide a reliable estimation of abundance in both conditions. There is no individual bias, whether people are familiar or not with its use. They could also be used for a quick estimation of larval treatment effectiveness, for the study of population dynamics and spatial distribution.
NASA Astrophysics Data System (ADS)
H, Dhaouadi; R, Zgueb; O, Riahi; F, Trabelsi; T, Othman
2016-05-01
In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the (E,T) phase diagram of the studied product can be obtained. In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.
Bi-color near infrared thermoreflectometry: a method for true temperature field measurement.
Sentenac, Thierry; Gilblas, Rémi; Hernandez, Daniel; Le Maoult, Yannick
2012-12-01
In a context of radiative temperature field measurement, this paper deals with an innovative method, called bicolor near infrared thermoreflectometry, for the measurement of true temperature fields without prior knowledge of the emissivity field of an opaque material. This method is achieved by a simultaneous measurement, in the near infrared spectral band, of the radiance temperature fields and of the emissivity fields measured indirectly by reflectometry. The theoretical framework of the method is introduced and the principle of the measurements at two wavelengths is detailed. The crucial features of the indirect measurement of emissivity are the measurement of bidirectional reflectivities in a single direction and the introduction of an unknown variable, called the "diffusion factor." Radiance temperature and bidirectional reflectivities are then merged into a bichromatic system based on Kirchhoff's laws. The assumption of the system, based on the invariance of the diffusion factor for two near wavelengths, and the value of the chosen wavelengths, are then discussed in relation to a database of several material properties. A thermoreflectometer prototype was developed, dimensioned, and evaluated. Experiments were carried out to outline its trueness in challenging cases. First, experiments were performed on a metallic sample with a high emissivity value. The bidirectional reflectivity was then measured from low signals. The results on erbium oxide demonstrate the power of the method with materials with high emissivity variations in near infrared spectral band.
Phase field approaches of bone remodeling based on TIP
NASA Astrophysics Data System (ADS)
Ganghoffer, Jean-François; Rahouadj, Rachid; Boisse, Julien; Forest, Samuel
2016-01-01
The process of bone remodeling includes a cycle of repair, renewal, and optimization. This adaptation process, in response to variations in external loads and chemical driving factors, involves three main types of bone cells: osteoclasts, which remove the old pre-existing bone; osteoblasts, which form the new bone in a second phase; osteocytes, which are sensing cells embedded into the bone matrix, trigger the aforementioned sequence of events. The remodeling process involves mineralization of the bone in the diffuse interface separating the marrow, which contains all specialized cells, from the newly formed bone. The main objective advocated in this contribution is the setting up of a modeling and simulation framework relying on the phase field method to capture the evolution of the diffuse interface between the new bone and the marrow at the scale of individual trabeculae. The phase field describes the degree of mineralization of this diffuse interface; it varies continuously between the lower value (no mineral) and unity (fully mineralized phase, e.g. new bone), allowing the consideration of a diffuse moving interface. The modeling framework is the theory of continuous media, for which field equations for the mechanical, chemical, and interfacial phenomena are written, based on the thermodynamics of irreversible processes. Additional models for the cellular activity are formulated to describe the coupling of the cell activity responsible for bone production/resorption to the kinetics of the internal variables. Kinetic equations for the internal variables are obtained from a pseudo-potential of dissipation. The combination of the balance equations for the microforce associated to the phase field and the kinetic equations lead to the Ginzburg-Landau equation satisfied by the phase field with a source term accounting for the dissipative microforce. Simulations illustrating the proposed framework are performed in a one-dimensional situation showing the evolution of
Surface profile and stress field evaluation using digital gradient sensing method
NASA Astrophysics Data System (ADS)
Miao, C.; Sundaram, B. M.; Huang, L.; Tippur, H. V.
2016-09-01
Shape and surface topography evaluation from measured orthogonal slope/gradient data is of considerable engineering significance since many full-field optical sensors and interferometers readily output such a data accurately. This has applications ranging from metrology of optical and electronic elements (lenses, silicon wafers, thin film coatings), surface profile estimation, wave front and shape reconstruction, to name a few. In this context, a new methodology for surface profile and stress field determination based on a recently introduced non-contact, full-field optical method called digital gradient sensing (DGS) capable of measuring small angular deflections of light rays coupled with a robust finite-difference-based least-squares integration (HFLI) scheme in the Southwell configuration is advanced here. The method is demonstrated by evaluating (a) surface profiles of mechanically warped silicon wafers and (b) stress gradients near growing cracks in planar phase objects.
Shalchi, A.
2010-08-15
To study the wandering of magnetic field lines is an important subject in theoretical physics. Results of field line random walk theories can be applied in plasma physics as well as astrophysics. Previous investigations are based on magnetostatic models. These models have been used in analytical work as well as in computer simulations to warrant mathematical and numerical tractability. To replace the magnetostatic model by a dynamical turbulence model is a difficult task. In the present article, a field line tracing method is used to describe field line wandering in dynamical magnetic turbulence. As examples different models are employed, namely, the plasma wave model, the damping model of dynamical turbulence, and the random sweeping model. It is demonstrated that the choice of the turbulence model has a very strong influence on the field line structure. It seems that if dynamical turbulence effects are included, Markovian diffusion can be found for other forms of the wave spectrum as in the magnetostatic model. Therefore, the results of the present paper are useful to specify turbulence models. As a further application we consider charged particle transport at early times.
The Influences of University-Based Coursework on Field Experience
ERIC Educational Resources Information Center
Beeth, Michael E.; Adadan, Emine
2006-01-01
This study explored the influence of university-based teacher education courses on preservice teachers as they engaged in the field-based portion of their preparation. Forty-two preservice teachers contributed reflective writings about the successes and challenges they faced during field experiences in light of knowledge and skills learned during…
How to Plan a Theme Based Field Day
ERIC Educational Resources Information Center
Shea, Scott A.; Fagala, Lisa M.
2006-01-01
Having a theme-based field day is a great way to get away from doing the traditional track-and-field type events, such as the softball throw, 50 yard dash, and sack race, year after year. In a theme-based field day format all stations or events are planned around a particular theme. This allows the teacher to be creative while also adding…
A new automatic baseline correction method based on iterative method
NASA Astrophysics Data System (ADS)
Bao, Qingjia; Feng, Jiwen; Chen, Fang; Mao, Wenping; Liu, Zao; Liu, Kewen; Liu, Chaoyang
2012-05-01
A new automatic baseline correction method for Nuclear Magnetic Resonance (NMR) spectra is presented. It is based on an improved baseline recognition method and a new iterative baseline modeling method. The presented baseline recognition method takes advantages of three baseline recognition algorithms in order to recognize all signals in spectra. While in the iterative baseline modeling method, besides the well-recognized baseline points in signal-free regions, the 'quasi-baseline points' in the signal-crowded regions are also identified and then utilized to improve robustness by preventing the negative regions. The experimental results on both simulated data and real metabolomics spectra with over-crowded peaks show the efficiency of this automatic method.
Precise full-field distortion rectification and evaluation method for a digital projector
NASA Astrophysics Data System (ADS)
Wang, Zhangying; Liu, Miao; Yang, Shourui; Huang, Shujun; Bai, Xuefei; Liu, Xiaohong; Zhu, Jigui; Liu, Xiaoli; Zhang, Zonghua
2016-10-01
Digital projectors have been widely used in many accuracy-sensitive fields. Although some calibration methods have been proposed to obtain the intrinsic parameters for a digital projector, especially the radial and tangential distortion, there are few studies on how to rectify the projected image to obtain an ideal projection pattern and further evaluate the results. In this paper, a precise full-field image rectification technique is proposed based on the principle of projector calibration. The pixel remapping and interpolation techniques are detailed step by step. All of the method's steps maintain subpixel accuracy. Moreover, a full-field verification method is presented to evaluate the effectiveness of the projector distortion procedure using a full-field phase map. A full-field non-linear distortion distribution map can be generated to represent distortion characteristics of nearly all the pixels of a projector in a very intuitive way. The experimental results validate and show the effectiveness of the proposed full-field rectification technique and evaluation method.
Precise full-field distortion rectification and evaluation method for a digital projector
NASA Astrophysics Data System (ADS)
Wang, Zhangying; Liu, Miao; Yang, Shourui; Huang, Shujun; Bai, Xuefei; Liu, Xiaohong; Zhu, Jigui; Liu, Xiaoli; Zhang, Zonghua
2016-08-01
Digital projectors have been widely used in many accuracy-sensitive fields. Although some calibration methods have been proposed to obtain the intrinsic parameters for a digital projector, especially the radial and tangential distortion, there are few studies on how to rectify the projected image to obtain an ideal projection pattern and further evaluate the results. In this paper, a precise full-field image rectification technique is proposed based on the principle of projector calibration. The pixel remapping and interpolation techniques are detailed step by step. All of the method's steps maintain subpixel accuracy. Moreover, a full-field verification method is presented to evaluate the effectiveness of the projector distortion procedure using a full-field phase map. A full-field non-linear distortion distribution map can be generated to represent distortion characteristics of nearly all the pixels of a projector in a very intuitive way. The experimental results validate and show the effectiveness of the proposed full-field rectification technique and evaluation method.
Reliability of field methods for estimating body fat.
Loenneke, Jeremy P; Barnes, Jeremy T; Wilson, Jacob M; Lowery, Ryan P; Isaacs, Melissa N; Pujol, Thomas J
2013-09-01
When health professionals measure the fitness levels of clients, body composition is usually estimated. In practice, the reliability of the measurement may be more important than the actual validity, as reliability determines how much change is needed to be considered meaningful. Therefore, the purpose of this study was to determine the reliability of two bioelectrical impedance analysis (BIA) devices (in athlete and non-athlete mode) and compare that to 3-site skinfold (SKF) readings. Twenty-one college students attended the laboratory on two occasions and had their measurements taken in the following order: body mass, height, SKF, Tanita body fat-350 (BF-350) and Omron HBF-306C. There were no significant pairwise differences between Visit 1 and Visit 2 for any of the estimates (P>0.05). The Pearson product correlations ranged from r = 0.933 for HBF-350 in the athlete mode (A) to r = 0.994 for SKF. The ICC's ranged from 0.93 for HBF-350(A) to 0.992 for SKF, and the MD's ranged from 1.8% for SKF to 5.1% for BF-350(A). The current study found that SKF and HBF-306C(A) were the most reliable (<2%) methods of estimating BF%, with the other methods (BF-350, BF-350(A), HBF-306C) producing minimal differences greater than 2%. In conclusion, the SKF method presented with the best reliability because of its low minimal difference, suggesting this method may be the best field method to track changes over time if you have an experienced tester. However, if technical error is a concern, the practitioner may use the HBF-306C(A) because it had a minimal difference value comparable to SKF. PMID:23701358
Vocabulary Teaching Based on Semantic-Field
ERIC Educational Resources Information Center
Wangru, Cao
2016-01-01
Vocabulary is an indispensable part of language and it is of vital importance for second language learners. Wilkins (1972) points out: "without grammar very little can be conveyed, without vocabulary nothing can be conveyed." Vocabulary teaching has experienced several stages characterized by grammatical-translation method, audio-lingual…
A Multipole Expansion Method for Analyzing Lightning Field Changes
NASA Technical Reports Server (NTRS)
Koshak, William J.; Krider, E. Philip; Murphy, Martin J.
1999-01-01
Changes in the surface electric field are frequently used to infer the locations and magnitudes of lightning-caused changes in thundercloud charge distributions. The traditional procedure is to assume that the charges that are effectively deposited by the flash can be modeled either as a single point charge (the Q model) or a point dipole (the P model). The Q model has four unknown parameters and provides a good description of many cloud-to-ground (CG) flashes. The P model has six unknown parameters and describes many intracloud (IC) discharges. In this paper we introduce a new analysis method that assumes that the change in the cloud charge can be described by a truncated multipole expansion, i.e., there are both monopole and dipole terms in the unknown source distribution, and both terms are applied simultaneously. This method can be used to analyze CG flashes that are accompanied by large changes in the cloud dipole moment and complex IC discharges. If there is enough information content in the measurements, the model can also be generalized to include quadrupole and higher order terms. The parameters of the charge moments are determined using a dme-dimensional grid search in combination with a linear inversion, and because of this, local minima in the error function and the associated solution ambiguities are avoided. The multipole method has been tested on computer-simulated sources and on natural lightning at the NASA Kennedy Space Center and U.S. Air Force Eastern Range.
63,65Cu NMR Method in a Local Field for Investigation of Copper Ore Concentrates
NASA Astrophysics Data System (ADS)
Gavrilenko, A. N.; Starykh, R. V.; Khabibullin, I. Kh.; Matukhin, V. L.
2015-01-01
To choose the most efficient method and ore beneficiation flow diagram, it is important to know physical and chemical properties of ore concentrates. The feasibility of application of the 63,65Cu nuclear magnetic resonance (NMR) method in a local field aimed at studying the properties of copper ore concentrates in the copper-iron-sulfur system is demonstrated. 63,65Cu NMR spectrum is measured in a local field for a copper concentrate sample and relaxation parameters (times T1 and T2) are obtained. The spectrum obtained was used to identify a mineral (chalcopyrite) contained in the concentrate. Based on the experimental data, comparative characteristics of natural chalcopyrite and beneficiated copper concentrate are given. The feasibility of application of the NMR method in a local field to explore mineral deposits is analyzed.
NASA Astrophysics Data System (ADS)
Wang, Xueying; Li, Jun; Sheng, Weidong; An, Wei; Du, Qinfeng
2015-10-01
ABSTRACT In Space-based optical system, during the tracking for closely spaced objects (CSOs), the traditional method with a constant false alarm rate(CFAR) detecting brings either more clutter measurements or the loss of target information. CSOs can be tracked as Extended targets because their features on optical sensor's pixel-plane. A pixel partition method under the framework of Markov random field(MRF) is proposed, simulation results indicate: the method proposed provides higher pixel partition performance than traditional method, especially when the signal-noise-rate is poor.
James, Kevin R; Dowling, David R
2008-09-01
In underwater acoustics, the accuracy of computational field predictions is commonly limited by uncertainty in environmental parameters. An approximate technique for determining the probability density function (PDF) of computed field amplitude, A, from known environmental uncertainties is presented here. The technique can be applied to several, N, uncertain parameters simultaneously, requires N+1 field calculations, and can be used with any acoustic field model. The technique implicitly assumes independent input parameters and is based on finding the optimum spatial shift between field calculations completed at two different values of each uncertain parameter. This shift information is used to convert uncertain-environmental-parameter distributions into PDF(A). The technique's accuracy is good when the shifted fields match well. Its accuracy is evaluated in range-independent underwater sound channels via an L(1) error-norm defined between approximate and numerically converged results for PDF(A). In 50-m- and 100-m-deep sound channels with 0.5% uncertainty in depth (N=1) at frequencies between 100 and 800 Hz, and for ranges from 1 to 8 km, 95% of the approximate field-amplitude distributions generated L(1) values less than 0.52 using only two field calculations. Obtaining comparable accuracy from traditional methods requires of order 10 field calculations and up to 10(N) when N>1.
Apparatus and method for producing an artificial gravitational field
NASA Technical Reports Server (NTRS)
Mccanna, Jason (Inventor)
1993-01-01
An apparatus and method is disclosed for producing an artificial gravitational field in a spacecraft by rotating the same around a spin axis. The centrifugal force thereby created acts as an artificial gravitational force. The apparatus includes an engine which produces a drive force offset from the spin axis to drive the spacecraft towards a destination. The engine is also used as a counterbalance for a crew cabin for rotation of the spacecraft. Mass of the spacecraft, which may include either the engine or crew cabin, is shifted such that the centrifugal force acting on that mass is no longer directed through the center of mass of the craft. This off-center centrifugal force creates a moment that counterbalances the moment produced by the off-center drive force to eliminate unwanted rotation which would otherwise be precipitated by the offset drive force.
Methods for Quantitative Interpretation of Retarding Field Analyzer Data
Calvey, J.R.; Crittenden, J.A.; Dugan, G.F.; Palmer, M.A.; Furman, M.; Harkay, K.
2011-03-28
Over the course of the CesrTA program at Cornell, over 30 Retarding Field Analyzers (RFAs) have been installed in the CESR storage ring, and a great deal of data has been taken with them. These devices measure the local electron cloud density and energy distribution, and can be used to evaluate the efficacy of different cloud mitigation techniques. Obtaining a quantitative understanding of RFA data requires use of cloud simulation programs, as well as a detailed model of the detector itself. In a drift region, the RFA can be modeled by postprocessing the output of a simulation code, and one can obtain best fit values for important simulation parameters with a chi-square minimization method.
Hybrid star structure with the Field Correlator Method
NASA Astrophysics Data System (ADS)
Burgio, G. F.; Zappalà, D.
2016-03-01
We explore the relevance of the color-flavor locking phase in the equation of state (EoS) built with the Field Correlator Method (FCM) for the description of the quark matter core of hybrid stars. For the hadronic phase, we use the microscopic Brueckner-Hartree-Fock (BHF) many-body theory, and its relativistic counterpart, i.e. the Dirac-Brueckner (DBHF). We find that the main features of the phase transition are directly related to the values of the quark-antiquark potential V1, the gluon condensate G2 and the color-flavor superconducting gap Δ. We confirm that the mapping between the FCM and the CSS (constant speed of sound) parameterization holds true even in the case of paired quark matter. The inclusion of hyperons in the hadronic phase and its effect on the mass-radius relation of hybrid stars is also investigated.
METHOD OF JOINING CARBIDES TO BASE METALS
Krikorian, N.H.; Farr, J.D.; Witteman, W.G.
1962-02-13
A method is described for joining a refractory metal carbide such as UC or ZrC to a refractory metal base such as Ta or Nb. The method comprises carburizing the surface of the metal base and then sintering the base and carbide at temperatures of about 2000 deg C in a non-oxidizing atmosphere, the base and carbide being held in contact during the sintering step. To reduce the sintering temperature and time, a sintering aid such as iron, nickel, or cobait is added to the carbide, not to exceed 5 wt%. (AEC)
Tls Field Data Based Intensity Correction for Forest Environments
NASA Astrophysics Data System (ADS)
Heinzel, J.; Huber, M. O.
2016-06-01
Terrestrial laser scanning (TLS) is increasingly used for forestry applications. Besides the three dimensional point coordinates, the 'intensity' of the reflected signal plays an important role in forestry and vegetation studies. The benefit of the signal intensity is caused by the wavelength of the laser that is within the near infrared (NIR) for most scanners. The NIR is highly indicative for various vegetation characteristics. However, the intensity as recorded by most terrestrial scanners is distorted by both external and scanner specific factors. Since details about system internal alteration of the signal are often unknown to the user, model driven approaches are impractical. On the other hand, existing data driven calibration procedures require laborious acquisition of separate reference datasets or areas of homogenous reflection characteristics from the field data. In order to fill this gap, the present study introduces an approach to correct unwanted intensity variations directly from the point cloud of the field data. The focus is on the variation over range and sensor specific distortions. Instead of an absolute calibration of the values, a relative correction within the dataset is sufficient for most forestry applications. Finally, a method similar to time series detrending is presented with the only pre-condition of a relative equal distribution of forest objects and materials over range. Our test data covers 50 terrestrial scans captured with a FARO Focus 3D S120 scanner using a laser wavelength of 905 nm. Practical tests demonstrate that our correction method removes range and scanner based alterations of the intensity.
Singular boundary method for global gravity field modelling
NASA Astrophysics Data System (ADS)
Cunderlik, Robert
2014-05-01
The singular boundary method (SBM) and method of fundamental solutions (MFS) are meshless boundary collocation techniques that use the fundamental solution of a governing partial differential equation (e.g. the Laplace equation) as their basis functions. They have been developed to avoid singular numerical integration as well as mesh generation in the traditional boundary element method (BEM). SBM have been proposed to overcome a main drawback of MFS - its controversial fictitious boundary outside the domain. The key idea of SBM is to introduce a concept of the origin intensity factors that isolate singularities of the fundamental solution and its derivatives using some appropriate regularization techniques. Consequently, the source points can be placed directly on the real boundary and coincide with the collocation nodes. In this study we deal with SBM applied for high-resolution global gravity field modelling. The first numerical experiment presents a numerical solution to the fixed gravimetric boundary value problem. The achieved results are compared with the numerical solutions obtained by MFS or the direct BEM indicating efficiency of all methods. In the second numerical experiments, SBM is used to derive the geopotential and its first derivatives from the Tzz components of the gravity disturbing tensor observed by the GOCE satellite mission. A determination of the origin intensity factors allows to evaluate the disturbing potential and gravity disturbances directly on the Earth's surface where the source points are located. To achieve high-resolution numerical solutions, the large-scale parallel computations are performed on the cluster with 1TB of the distributed memory and an iterative elimination of far zones' contributions is applied.
Defeaturing CAD models using a geometry-based size field and facet-based reduction operators.
Quadros, William Roshan; Owen, Steven James
2010-04-01
We propose a method to automatically defeature a CAD model by detecting irrelevant features using a geometry-based size field and a method to remove the irrelevant features via facet-based operations on a discrete representation. A discrete B-Rep model is first created by obtaining a faceted representation of the CAD entities. The candidate facet entities are then marked for reduction by using a geometry-based size field. This is accomplished by estimating local mesh sizes based on geometric criteria. If the field value at a facet entity goes below a user specified threshold value then it is identified as an irrelevant feature and is marked for reduction. The reduction of marked facet entities is primarily performed using an edge collapse operator. Care is taken to retain a valid geometry and topology of the discrete model throughout the procedure. The original model is not altered as the defeaturing is performed on a separate discrete model. Associativity between the entities of the discrete model and that of original CAD model is maintained in order to decode the attributes and boundary conditions applied on the original CAD entities onto the mesh via the entities of the discrete model. Example models are presented to illustrate the effectiveness of the proposed approach.
Using Field Trips and Field-Based Laboratories to Teach Undergraduate Soil Science
NASA Astrophysics Data System (ADS)
Brevik, Eric C.; Steffan, Joshua; Hopkins, David
2015-04-01
Classroom activities can provide important background information allowing students to understand soils. However, soils are formed in nature; therefore, understanding their properties and spatial relationships in the field is a critical component for gaining a comprehensive and holistic understanding of soils. Field trips and field-based laboratories provide students with the field experiences and skills needed to gain this understanding. Field studies can 1) teach students the fundamentals of soil descriptions, 2) expose students to features (e.g., structure, redoximorphic features, clay accumulation, etc.) discussed in the classroom, and 3) allow students to verify for themselves concepts discussed in the more theoretical setting of the classroom. In each case, actually observing these aspects of soils in the field reinforces and improves upon classroom learning and comprehension. In addition, the United States Department of Agriculture's Natural Resources Conservation Service has identified a lack of fundamental field skills as a problem when they hire recent soil science graduates, thereby demonstrating the need for increased field experiences for the modern soil science student. In this presentation we will provide examples of field trips and field-based laboratories that we have designed for our undergraduate soil science classes, discuss the learning objectives, and provide several examples of comments our students have made in response to these field experiences.
A free-field method to calibrate bone conduction transducers.
Pollard, Kimberly A; Tran, Phuong K; Letowski, Tomasz R
2013-02-01
Bone conduction communication systems employ a variety of transducers with different physical and electroacoustic properties, and these transducers may be worn at various skull locations. Testing these systems thus requires a reliable means of transducer calibration that can be implemented across different devices, skull locations, and settings. Unfortunately, existing calibration standards do not meet these criteria. Audiometric bone conduction standards focus on only one device model and on limited skull locations. Furthermore, while mechanical couplers may be used for calibration, the general human validity of their results is suspect. To address the need for more flexible, human-centered calibration methods, the authors investigated a procedure for bone transducer calibration, analogous to free-field methods for calibrating air conduction headphones. Participants listened to1s third-octave noise bands (125-12,500 Hz) alternating between a bone transducer and a loudspeaker and adjusted the bone transducer to match the perceived loudness of the loudspeaker at each test frequency. Participants tested two transducer models and two skull locations. Intra- and inter-subject reliability was high, and the resulting data differed by transducer, by location, and from the mechanical coupler. The described procedure is flexible to transducer model and skull location, requires only basic equipment, and directly yields perceptual data. PMID:23363104
Generalized method of eigenoscillations for near-field optical microscopy
NASA Astrophysics Data System (ADS)
Jiang, Bor-Yuan; Zhang, Lingfeng; Castro Neto, Antonio; Basov, Dimitri; Fogler, Michael
2015-03-01
Electromagnetic interaction between a sub-wavelength particle (the ``probe'') and a material surface (the ``sample'') is studied theoretically. The interaction is shown to be governed by a series of resonances (eigenoscillations), corresponding to surface polariton modes localized near the probe. The resonance parameters depend on the dielectric function and geometry of the probe, as well as the surface reflectivity of the material. Calculation of such resonances is carried out for several axisymmetric particle shapes (spherical, spheroidal, and pear-shaped). For spheroids an efficient numerical method is proposed, capable of handling cases of large or strongly momentum-dependent surface reflectivity. The method is applied to modeling near-field spectroscopy studies of various materials. For highly resonant materials such as aluminum oxide (by itself or covered with graphene) a rich structure of the simulated signal is found, including multi-peak spectra and nonmonotonic approach curves. These features have a strong dependence on physical parameters, e.g., the probe shape. For less resonant materials such as silicon oxide the dependence is weaker, and the spheroid model is generally applicable.
Comparison of aquatic macroinvertebrate samples collected using different field methods
Lenz, Bernard N.; Miller, Michael A.
1996-01-01
Government agencies, academic institutions, and volunteer monitoring groups in the State of Wisconsin collect aquatic macroinvertebrate data to assess water quality. Sampling methods differ among agencies, reflecting the differences in the sampling objectives of each agency. Lack of infor- mation about data comparability impedes data shar- ing among agencies, which can result in duplicated sampling efforts or the underutilization of avail- able information. To address these concerns, com- parisons were made of macroinvertebrate samples collected from wadeable streams in Wisconsin by personnel from the U.S. Geological Survey- National Water Quality Assessment Program (USGS-NAWQA), the Wisconsin Department of Natural Resources (WDNR), the U.S. Department of Agriculture-Forest Service (USDA-FS), and volunteers from the Water Action Volunteer-Water Quality Monitoring Program (WAV). This project was part of the Intergovernmental Task Force on Monitoring Water Quality (ITFM) Wisconsin Water Resources Coordination Project. The numbers, types, and environmental tolerances of the organ- isms collected were analyzed to determine if the four different field methods that were used by the different agencies and volunteer groups provide comparable results. Additionally, this study com- pared the results of samples taken from different locations and habitats within the same streams.
An acoustic intensity-based method and its aeroacoustic applications
NASA Astrophysics Data System (ADS)
Yu, Chao
Aircraft noise prediction and control is one of the most urgent and challenging tasks worldwide. A hybrid approach is usually considered for predicting the aerodynamic noise. The approach separates the field into aerodynamic source and acoustic propagation regions. Conventional CFD solvers are typically used to evaluate the flow field in the source region. Once the sound source is predicted, the linearized Euler Equations (LEE) can be used to extend the near-field CFD solution to the mid-field acoustic radiation. However, the far-field extension is very time consuming and always prohibited by the excessive computer memory requirements. The FW-H method, instead, predicts the far-field radiation using the flow-field quantities on a closed control surface (that encloses the entire aerodynamic source region) if the wave equation is assumed outside. The surface integration, however, has to be carried out for each far-field location. This would be still computationally intensive for a practical 3D problem even though the intensity in terms of the CPU time has been much decreased compared with that required by the LEE methods. For an accurate far-field prediction, the other difficulty of using the FW-H method is that the complete control surface may be infeasible to accomplish for most practical applications. Motivated by the need for the accurate and efficient far-field prediction techniques, an Acoustic Intensity-Based Method (AIBM) has been developed based on an acoustic input from an OPEN control surface. The AIBM assumes that the sound propagation is governed by the modified Helmholtz equation on and outside a control surface that encloses all the nonlinear effects and noise sources. The prediction of the acoustic radiation field is carried out by the inverse method with an input of acoustic pressure derivative and its simultaneous, co-located acoustic pressure. The reconstructed acoustic radiation field using the AIBM is unique due to the unique continuation theory
Flexible and Transparent Field Emission Devices based on Graphene-Nanowire Hybrid Structures
NASA Astrophysics Data System (ADS)
Arif, Muhammad; Heo, Kwang; Lee, Byung Yang; Seo, David H.; Seo, Sunae; Jian, Jikang; Hong, Seunghun
2011-03-01
Recent developments in wafer scale synthesis and transfer of graphene have made it possible to fabricate electrodes for versatile flexible devices. However, a flexible and transparent graphene-based field emission device has not been explored yet. Herein, we report the fabrication of flexible and transparent field emission devices based on graphene-nanowire hybrid structures. In this work, we successfully grew vertically-aligned Au nanowires on graphene surface using an electrochemical method and utilized it as a cathode. We also utilized a graphene electrode for an anode resulting in a transparent and flexible field emission device. Our field emission devices can be bent down to 22 mm radius of curvature without any significant change in its field emission currents. This flexible and transparent field emission device based on graphene-nanowire hybrid structures will utilized for various applications such as field emission displays, x-ray tubes, and pressure sensors.
A copula-based downscaling methodology of RCM precipitation fields
NASA Astrophysics Data System (ADS)
Lorenz, Manuel
2016-04-01
Many hydrological studies require long term precipitation time series at a fine spatial resolution. While regional climate models are nowadays capable of simulating reasonable high-resolution precipitation fields, the long computing time makes the generation of such long term time series often infeasible for practical purposes. We introduce a comparatively fast stochastic approach to simulate precipitation fields which resemble the spatial dependencies and density distributions of the dynamic model. Nested RCM simulations at two different spatial resolutions serve as a training set to derive the statistics which will then be used in a random path simulation where fine scale precipitation values are simulated from a multivariate Gaussian Copula. The chosen RCM is the Weather Research and Forecasting Model (WRF). Simulated daily precipitation fields of the RCM are based on ERA-Interim reanalysis data from 1971 to 2000 and are available at a spatial resolution of 42 km (Europe) and 7 km (Germany). In order to evaluate the method, the stochastic algorithm is applied to the nested German domain and the resulting spatial dependencies and density distributions are compared to the original 30 years long 7 km WRF simulations. Preliminary evaluations based on QQ-plots for one year indicate that the distributions of the downscaled values are very similar to the original values for most cells. In this presentation, a detailed overview of the stochastic downscaling algorithm and the evaluation of the long term simulations are given. Additionally, an outlook for a 5 km and 1 km downscaling experiment for urban hydrology studies is presented.
Liu, Feng; Crozier, Stuart
2004-05-21
The precise evaluation of electromagnetic field (EMF) distributions inside biological samples is becoming an increasingly important design requirement for high field MRI systems. In evaluating the induced fields caused by magnetic field gradients and RF transmitter coils, a multilayered dielectric spherical head model is proposed to provide a better understanding of electromagnetic interactions when compared to a traditional homogeneous head phantom. This paper presents Debye potential (DP) and Dyadic Green's function (DGF)-based solutions of the EMFs inside a head-sized, stratified sphere with similar radial conductivity and permittivity profiles as a human head. The DP approach is formulated for the symmetric case in which the source is a circular loop carrying a harmonic-formed current over a wide frequency range. The DGF method is developed for generic cases in which the source may be any kind of RF coil whose current distribution can be evaluated using the method of moments. The calculated EMFs can then be used to deduce MRI imaging parameters. The proposed methods, while not representing the full complexity of a head model, offer advantages in rapid prototyping as the computation times are much lower than a full finite difference time domain calculation using a complex head model. Test examples demonstrate the capability of the proposed models/methods. It is anticipated that this model will be of particular value for high field MRI applications, especially the rapid evaluation of RF resonator (surface and volume coils) and high performance gradient set designs.
Ansari, N; Hou, E H; Yu, Y
1995-01-01
Reports a new method for optimizing satellite broadcasting schedules based on the Hopfield neural model in combination with the mean field annealing theory. A clamping technique is used with an associative matrix, thus reducing the dimensions of the solution space. A formula for estimating the critical temperature for the mean field annealing procedure is derived, hence enabling the updating of the mean field theory equations to be more economical. Several factors on the numerical implementation of the mean field equations using a straightforward iteration method that may cause divergence are discussed; methods to avoid this kind of divergence are also proposed. Excellent results are consistently found for problems of various sizes.
Full field imaging based instantaneous hyperspectral absolute refractive index measurement
Baba, Justin S; Boudreaux, Philip R
2012-01-01
Multispectral refractometers typically measure refractive index (RI) at discrete monochromatic wavelengths via a serial process. We report on the demonstration of a white light full field imaging based refractometer capable of instantaneous multispectral measurement of absolute RI of clear liquid/gel samples across the entire visible light spectrum. The broad optical bandwidth refractometer is capable of hyperspectral measurement of RI in the range 1.30 1.70 between 400nm 700nm with a maximum error of 0.0036 units (0.24% of actual) at 414nm for a = 1.50 sample. We present system design and calibration method details as well as results from a system validation sample.
Polyfluorene-based organic field-effect transistors
NASA Astrophysics Data System (ADS)
Hamilton, Michael C.
and demonstrated the combination of several physical phenomena, including slow carrier transport and the existence of few reversible and many irreversible trap states. A relatively low (65°C) optimal operating temperature of organic-based devices was observed. The trap states were further characterized using the photodischarge method to investigate the kinetics and distribution of trap states. A narrow distribution of trap states at 0.3eV above the valence band was found, which is consistent with field-effect mobility and bias temperature stress results.
Teaching Geographic Field Methods to Cultural Resource Management Technicians
ERIC Educational Resources Information Center
Mires, Peter B.
2004-01-01
There are perhaps 10,000 technicians in the United States who work in the field known as cultural resource management (CRM). The typical field technician possesses a bachelor's degree in anthropology, geography, or a closely allied discipline. The author's experience has been that few CRM field technicians receive adequate undergraduate training…
Creating analytically divergence-free velocity fields from grid-based data
NASA Astrophysics Data System (ADS)
Ravu, Bharath; Rudman, Murray; Metcalfe, Guy; Lester, Daniel R.; Khakhar, Devang V.
2016-10-01
We present a method, based on B-splines, to calculate a C2 continuous analytic vector potential from discrete 3D velocity data on a regular grid. A continuous analytically divergence-free velocity field can then be obtained from the curl of the potential. This field can be used to robustly and accurately integrate particle trajectories in incompressible flow fields. Based on the method of Finn and Chacon (2005) [10] this new method ensures that the analytic velocity field matches the grid values almost everywhere, with errors that are two to four orders of magnitude lower than those of existing methods. We demonstrate its application to three different problems (each in a different coordinate system) and provide details of the specifics required in each case. We show how the additional accuracy of the method results in qualitatively and quantitatively superior trajectories that results in more accurate identification of Lagrangian coherent structures.
Model-Based Method for Sensor Validation
NASA Technical Reports Server (NTRS)
Vatan, Farrokh
2012-01-01
Fault detection, diagnosis, and prognosis are essential tasks in the operation of autonomous spacecraft, instruments, and in situ platforms. One of NASA s key mission requirements is robust state estimation. Sensing, using a wide range of sensors and sensor fusion approaches, plays a central role in robust state estimation, and there is a need to diagnose sensor failure as well as component failure. Sensor validation can be considered to be part of the larger effort of improving reliability and safety. The standard methods for solving the sensor validation problem are based on probabilistic analysis of the system, from which the method based on Bayesian networks is most popular. Therefore, these methods can only predict the most probable faulty sensors, which are subject to the initial probabilities defined for the failures. The method developed in this work is based on a model-based approach and provides the faulty sensors (if any), which can be logically inferred from the model of the system and the sensor readings (observations). The method is also more suitable for the systems when it is hard, or even impossible, to find the probability functions of the system. The method starts by a new mathematical description of the problem and develops a very efficient and systematic algorithm for its solution. The method builds on the concepts of analytical redundant relations (ARRs).
Matched field localization based on CS-MUSIC algorithm
NASA Astrophysics Data System (ADS)
Guo, Shuangle; Tang, Ruichun; Peng, Linhui; Ji, Xiaopeng
2016-04-01
The problem caused by shortness or excessiveness of snapshots and by coherent sources in underwater acoustic positioning is considered. A matched field localization algorithm based on CS-MUSIC (Compressive Sensing Multiple Signal Classification) is proposed based on the sparse mathematical model of the underwater positioning. The signal matrix is calculated through the SVD (Singular Value Decomposition) of the observation matrix. The observation matrix in the sparse mathematical model is replaced by the signal matrix, and a new concise sparse mathematical model is obtained, which means not only the scale of the localization problem but also the noise level is reduced; then the new sparse mathematical model is solved by the CS-MUSIC algorithm which is a combination of CS (Compressive Sensing) method and MUSIC (Multiple Signal Classification) method. The algorithm proposed in this paper can overcome effectively the difficulties caused by correlated sources and shortness of snapshots, and it can also reduce the time complexity and noise level of the localization problem by using the SVD of the observation matrix when the number of snapshots is large, which will be proved in this paper.
Examples of Information Technology in Field-based Educational Settings
NASA Astrophysics Data System (ADS)
Knoop, P.; van der Pluijm, B.; Dey, E.; Burn, H.
2007-12-01
Over the last five years we have utilized ruggedized Tablet PCs and Pocket PCs in a variety of summer field courses at our Camp Davis Rocky Mountain Field Station, near Jackson, WY, as well as during departmental field trips. The courses involved range from upper-level field geology to lower-level introductory geology, as well as a mid-level environmental science course. During this period we gained a lot of experience with how to integrate information technology in field courses and field trips, as we experimented with a range of hardware and software combinations as well as different teaching approaches, some more successful than others. During much of this time we have also collaborated with external educational researchers to help us assess and understand the impact of this evolving approach to field-based instruction. Presented here are some example cases of how information technology can be used in the field for educational purposes, such as mapping projects in field courses, as a digital field notebook and reference library on field trips, and to support a mobile classroom while students are dispersed among vehicles or across a field area. We also present results from the educational evaluation of this work, which indicate that students see information technology as an important tool for their work, rather than as a novelty, and that it provides them with important visualization capabilities to enhance their understand that are not available with traditional paper mapping techniques.
Evidence-Based Practice: Integrating Classroom Curriculum and Field Education
ERIC Educational Resources Information Center
Tuchman, Ellen; Lalane, Monique
2011-01-01
This article describes the use of problem-based learning to teach the scope and consequences of evidence-based practices in mental health through an innovative assignment that integrates classroom and field learning. The authors illustrate the planning and implementation of the Evidence-Based Practice: Integrating Classroom Curriculum and Field…
NASA Astrophysics Data System (ADS)
Finke, G.; Kujawińska, M.; Kozacki, T.; Zaperty, W.
2016-09-01
In this paper we propose a method which allows to overcome the basic functional problems in holographic displays with naked eye observation caused by delivering too small images visible in narrow viewing angles. The solution is based on combining the spatiotemporal multiplexing method with a 4f optical system. It enables to increase an aperture of a holographic display and extend the angular visual field of view. The applicability of the modified display is evidenced by Wigner distribution analysis of holographic imaging with spatiotemporal multiplexing method and by the experiments performed at the display demonstrator.
2D ESR image reconstruction from 1D projections using the modulated field gradient method
NASA Astrophysics Data System (ADS)
Páli, T.; Sass, L.; Horvat, L. I.; Ebert, B.
A method for the reconstruction of 2D ESR images from 1 D projections which is based on the modulated field gradient method has been explored. The 2D distribution of spin-labeled stearic acid in oriented and unoriented dimyristoyl phosphatidylcholine multilayers on a flat quartz support was determined. Such samples are potentially useful for the determination of lipid lateral diffusion in oriented multilayers by monitoring the spreading of a sharp concentration profile in one or two dimensions. The limitations of the method are discussed and the improvements which are needed for dynamic measurements are outlined.
Integrating Field-Based Research into the Classroom: An Environmental Sampling Exercise
ERIC Educational Resources Information Center
DeSutter, T.; Viall, E.; Rijal, I.; Murdoff, M.; Guy, A.; Pang, X.; Koltes, S.; Luciano, R.; Bai, X.; Zitnick, K.; Wang, S.; Podrebarac, F.; Casey, F.; Hopkins, D.
2010-01-01
A field-based, soil methods, and instrumentation course was developed to expose graduate students to numerous strategies for measuring soil parameters. Given the northern latitude of North Dakota State University and the rapid onset of winter, this course met once per week for the first 8 weeks of the fall semester and centered on the field as a…
Thermodynamic properties of mixed-spin chains in magnetic field by the transfer matrix method
NASA Astrophysics Data System (ADS)
Fu, H. H.; Yao, K. L.; Liu, Z. L.
2006-10-01
Motivated by recent experimental synthesis of molecule-based ferrimagnetics, we have investigated the thermodynamic properties of one-dimensional antiferromagnetic-ferromagnetic mixed spin- {1}/{2} lozenge chain in external magnetic fields at low temperature, using the transfer matrix method. The magnetization and the specific heat of the spin system have been evaluated numerically from the free energy. The magnetization as a function of the magnetic field at low temperature shows step-like plateau characterized by three critical magnetic fields, which reflects the competing effect of magnetic interactions and thermal fluctuations. The double-peak structure in the curves of the specific heat is also found, which comes from the huge variation of the long-range order parameters. Our results show that the thermodynamic properties of the mixed spin- {1}/{2} molecule-based ferrimagnetics are very analogous to the behaviors of the spin-1 and spin- {1}/{2} mixed antiferromagentic chain.
On the no-field method for void time determination in flow field-flow fractionation.
Martin, Michel; Hoyos, Mauricio
2011-07-01
Elution time measurements of colloidal particles injected in a symmetrical flow field-flow fractionation (flow FFF) system when the inlet and outlet cross-flow connections are closed have been performed. This no-field method has been proposed earlier for void time (and void volume) determination in flow FFF Giddings et al. (1977). The elution times observed were much larger than expected on the basis of the channel geometrical volume and the flow rate. In order to explain these discrepancies, a flow model allowing the carrier liquid to flow through the porous walls toward the reservoirs located behind the porous elements and along these reservoirs was developed. The ratio between the observed elution time and expected one is found to depend only on a parameter which is a function of the effective permeability and thickness of the porous elements and of the channel thickness and length. The permeabilities of the frits used in the system were measured. Their values lead to predicted elution times in reasonable agreement with experimental ones, taking into account likely membrane protrusion inside the channel on system assembly. They comfort the basic feature of the flow model, in the no-field case. The carrier liquid mostly bypasses the channel to flow along the system mainly in the reservoir. It flows through the porous walls toward the reservoirs near channel inlet and again through the porous walls from the reservoirs to the channel near channel outlet before exiting the system. In order to estimate the extent of this bypassing process, it is desirable that the hydrodynamic characteristics of the permeable elements (permeability and thickness) are provided by flow FFF manufacturers. The model applies to symmetrical as well as asymmetrical flow FFF systems. PMID:21256498
Manifold based methods in facial expression recognition
NASA Astrophysics Data System (ADS)
Xie, Kun
2013-07-01
This paper describes a novel method for facial expression recognition based on non-linear manifold techniques. The graph-based algorithms are designed to treat structure in data, and regularize accordingly. This same goal is shared by several other algorithms, from linear method principal components analysis (PCA) to modern variants such as Laplacian eigenmaps. In this paper we focus on manifold learning for dimensionality reduction and clustering using Laplacian eigenmaps for facial expression recognition. We evaluate the algorithm by using all the pixels and selected features respectively and compare the performance of the proposed non-linear manifold method with the previous linear manifold approach, and the non linear method produces higher recognition rate than the facial expression representation using linear methods.
Graphical Methods for Quantifying Macromolecules through Bright Field Imaging
Chang, Hang; DeFilippis, Rosa Anna; Tlsty, Thea D.; Parvin, Bahram
2008-08-14
Bright ?eld imaging of biological samples stained with antibodies and/or special stains provides a rapid protocol for visualizing various macromolecules. However, this method of sample staining and imaging is rarely employed for direct quantitative analysis due to variations in sample fixations, ambiguities introduced by color composition, and the limited dynamic range of imaging instruments. We demonstrate that, through the decomposition of color signals, staining can be scored on a cell-by-cell basis. We have applied our method to Flbroblasts grown from histologically normal breast tissue biopsies obtained from two distinct populations. Initially, nuclear regions are segmented through conversion of color images into gray scale, and detection of dark elliptic features. Subsequently, the strength of staining is quanti?ed by a color decomposition model that is optimized by a graph cut algorithm. In rare cases where nuclear signal is significantly altered as a result of samplepreparation, nuclear segmentation can be validated and corrected. Finally, segmented stained patterns are associated with each nuclear region following region-based tessellation. Compared to classical non-negative matrix factorization, proposed method (i) improves color decomposition, (ii) has a better noise immunity, (iii) is more invariant to initial conditions, and (iv) has a superior computing performance
Cultivating Kuumba: Applying Art Based Strategies to Any Field
ERIC Educational Resources Information Center
Ellis, Auburn Elizabeth
2015-01-01
There are many contemporary issues to address in adult education. This paper explores art-based strategies and the utilization of creativity (Kuumba) to expand learning for global communities in any field of practice. Benefits of culturally grounded approaches to adult education are discussed. Images from ongoing field research can be viewed at…
Evaluation of different field methods for measuring soil water infiltration
NASA Astrophysics Data System (ADS)
Pla-Sentís, Ildefonso; Fonseca, Francisco
2010-05-01
Soil infiltrability, together with rainfall characteristics, is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the direct measurement of water infiltration rates or its indirect deduction from other soil characteristics or properties has become indispensable for the evaluation and modelling of the previously mentioned processes. Indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, have demonstrated to be of limited value in most of the cases. Direct "in situ" field evaluations have to be preferred in any case. In this contribution we present the results of past experiences in the measurement of soil water infiltration rates in many different soils and land conditions, and their use for deducing soil water balances under variable climates. There are also presented and discussed recent results obtained in comparing different methods, using double and single ring infiltrometers, rainfall simulators, and disc permeameters, of different sizes, in soils with very contrasting surface and profile characteristics and conditions, including stony soils and very sloping lands. It is concluded that there are not methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the surface
Annular subaperture stitching method based on autocollimation
NASA Astrophysics Data System (ADS)
Yiwei, Chen; Erlong, Miao; Yongxin, Sui; Huaijiang, Yang
2014-11-01
In this paper, we propose an annular subaperture stitching method based on an autocollimation method to relax the requirements on mechanical location accuracy. In this approach, we move a ball instead of the interferometer and the aspheric surface so that testing results for adjacent annular subapertures are registered. Thus, the stitching algorithm can easily stitch the subaperture testing results together when large mechanical location errors exist. To verify this new method, we perform a simulation experiment. The simulation results demonstrate that this method can stitch together the subaperture testing results under large mechanical location errors.
ERIC Educational Resources Information Center
Angeli, Charoula; Valanides, Nicos
2013-01-01
The present study investigated the problem-solving performance of 101 university students and their interactions with a computer modeling tool in order to solve a complex problem. Based on their performance on the hidden figures test, students were assigned to three groups of field-dependent (FD), field-mixed (FM), and field-independent (FI)…
NASA Astrophysics Data System (ADS)
Koide, T.; Kodama, T.
2015-09-01
The stochastic variational method (SVM) is the generalization of the variational approach to systems described by stochastic variables. In this paper, we investigate the applicability of SVM as an alternative field-quantization scheme, by considering the complex Klein-Gordon equation. There, the Euler-Lagrangian equation for the stochastic field variables leads to the functional Schrödinger equation, which can be interpreted as the Euler (ideal fluid) equation in the functional space. The present formulation is a quantization scheme based on commutable variables, so that there appears no ambiguity associated with the ordering of operators, e.g., in the definition of Noether charges.
PCB current identification based on near-field measurements using preconditioning and regularization
NASA Astrophysics Data System (ADS)
Rinas, Denis; Ahl, Patrick; Frei, Stephan
2016-09-01
Radiated electromagnetic fields from a PCB can be estimated when the source current distribution is known. From a measured near-field distribution, the PCB source current distribution can be found. Accuracy depends on the measurement method and its limitations, the radiation model and the choice of the observation area. Many known methods are based on optimization algorithms for inverse problems that vary a set of elementary radiation sources and create a radiation model. However, apart from the time-consuming optimization process, such methods find one possible solution for a near-field distribution. As this distribution might not reflect the real current distribution, accuracy outside of near-field scan area can be low. Furthermore numerical problems can often be observed. Solving the given inverse problem with a system of linear equations and complex near-field data it can be very sensitive to noise. Regularization methods and an adjusted preconditioning can increase the accuracy. In this paper, an improved radiation model creation approach based on complex near-field data is presented. This approach is based on regularization methods and extended by current estimations from near-field data. Preconditioning is done considering some physical properties of the PCB and its possible current paths. Accuracy and stability of the method are investigated in the presence of noisy data.
Graphene-based field effect transistors for radiation-induced field sensing
NASA Astrophysics Data System (ADS)
Di Gaspare, Alessandra; Valletta, Antonio; Fortunato, Guglielmo; Larciprete, Rosanna; Mariucci, Luigi; Notargiacomo, Andrea; Cimino, Roberto
2016-07-01
We propose the implementation of graphene-based field effect transistor (FET) as radiation sensor. In the proposed detector, graphene obtained via chemical vapor deposition is integrated into a Si-based field effect device as the gate readout electrode, able to sense any change in the field distribution induced by ionization in the underneath absorber, because of the strong variation in the graphene conductivity close to the charge neutrality point. Different 2-dimensional layered materials can be envisaged in this kind of device.
Wei, Zhiliang; Lin, Liangjie; Lin, Yanqin E-mail: chenz@xmu.edu.cn; Chen, Zhong E-mail: chenz@xmu.edu.cn; Chen, Youhe
2014-09-29
In nuclear magnetic resonance (NMR) technique, it is of great necessity and importance to obtain high-resolution spectra, especially under inhomogeneous magnetic fields. In this study, a method based on partial homogeneity is proposed for retrieving high-resolution one-dimensional NMR spectra under inhomogeneous fields. Signals from series of small voxels, which characterize high resolution due to small sizes, are recorded simultaneously. Then, an inhomogeneity correction algorithm is developed based on pattern recognition to correct the influence brought by field inhomogeneity automatically, thus yielding high-resolution information. Experiments on chemical solutions and fish spawn were carried out to demonstrate the performance of the proposed method. The proposed method serves as a single radiofrequency pulse high-resolution NMR spectroscopy under inhomogeneous fields and may provide an alternative of obtaining high-resolution spectra of in vivo living systems or chemical-reaction systems, where performances of conventional techniques are usually degenerated by field inhomogeneity.
Melamine sensing based on evanescent field enhanced optical fiber sensor
NASA Astrophysics Data System (ADS)
Luo, Ji; Yao, Jun; Wang, Wei-min; Zhuang, Xu-ye; Ma, Wen-ying; Lin, Qiao
2013-08-01
Melamine is an insalubrious chemical, and has been frequently added into milk products illegally, to make the products more protein-rich. However, it can cause some various diseases, such as kidney stones and bladder cancer. In this paper, a novel optical fiber sensor with high sensitivity based on absorption of the evanescent field for melamine detection is successfully proposed and developed. Different concentrations of melamine changing from 0 to 10mg/mL have been detected using the micro/nano-sensing fiber decorated with silver nanoparticles cluster layer. As the concentration increases, the sensing fiber's output intensity gradually deceases and the absorption of the analyte becomes large. The concentration changing of 1mg/ml can cause the absorbance varying 0.664 and the limit of the melamine detectable concentration is 1ug/mL. Besides, the coupling properties between silver nanoparticles have also been analyzed by the FDTD method. Overall, this evanescent field enhanced optical fiber sensor has potential to be used in oligo-analyte detection and will promote the development of biomolecular and chemical sensing applications.
Laser-field-induced surface-hopping method for the simulation and control of ultrafast photodynamics
Mitric, Roland; Petersen, Jens; Bonacic-Koutecky, Vlasta
2009-05-15
We present the semiclassical laser-field-induced surface-hopping method for the simulation and control of coupled electron-nuclear dynamics in complex molecular systems including all degrees of freedom. Our approach is based on the Wigner representation of quantum mechanics. The combination of the molecular dynamics 'on the fly' employing quantum initial conditions with the surface-hopping procedure allows for the treatment of the electronic transitions induced by the laser field. Our semiclassical approach reproduced accurately exact quantum dynamics in a two-electronic-state model system. We demonstrate the scope of our method on the example of the optimal pump-dump control of the trans-cis isomerization of a prototypical Schiff base molecular switch. Our results show that selective photochemistry can be achieved by shaped laser pulses which open new dynamical pathways by suppressing the isomerization through the conical intersections between electronic states.
A new method to measure galaxy bias by combining the density and weak lensing fields
NASA Astrophysics Data System (ADS)
Pujol, Arnau; Chang, Chihway; Gaztañaga, Enrique; Amara, Adam; Refregier, Alexandre; Bacon, David J.; Carretero, Jorge; Castander, Francisco J.; Crocce, Martin; Fosalba, Pablo; Manera, Marc; Vikram, Vinu
2016-10-01
We present a new method to measure redshift-dependent galaxy bias by combining information from the galaxy density field and the weak lensing field. This method is based on the work of Amara et al., who use the galaxy density field to construct a bias-weighted convergence field κg. The main difference between Amara et al.'s work and our new implementation is that here we present another way to measure galaxy bias, using tomography instead of bias parametrizations. The correlation between κg and the true lensing field κ allows us to measure galaxy bias using different zero-lag correlations, such as <κgκ>/<κκ> or <κgκg>/<κgκ>. Our method measures the linear bias factor on linear scales, under the assumption of no stochasticity between galaxies and matter. We use the Marenostrum Institut de Ciències de l'Espai (MICE) simulation to measure the linear galaxy bias for a flux-limited sample (i < 22.5) in tomographic redshift bins using this method. This article is the first that studies the accuracy and systematic uncertainties associated with the implementation of the method and the regime in which it is consistent with the linear galaxy bias defined by projected two-point correlation functions (2PCF). We find that our method is consistent with a linear bias at the per cent level for scales larger than 30 arcmin, while non-linearities appear at smaller scales. This measurement is a good complement to other measurements of bias, since it does not depend strongly on σ8 as do the 2PCF measurements. We will apply this method to the Dark Energy Survey Science Verification data in a follow-up article.
Kraus, B.; Tittel, W.; Gisin, N.; Nilsson, M.; Kroell, S.; Cirac, J. I.
2006-02-15
We propose a method for efficient storage and recall of arbitrary nonstationary light fields, such as, for instance, single photon time-bin qubits or intense fields, in optically dense atomic ensembles. Our approach to quantum memory is based on controlled, reversible, inhomogeneous broadening and relies on a hidden time-reversal symmetry of the optical Bloch equations describing the propagation of the light field. We briefly discuss experimental realizations of our proposal.
NASA Astrophysics Data System (ADS)
Guo, Nannan; Zhou, Xuhua; Wu, Bin
2016-04-01
In this paper, based on simultaneous solution approach, using Gravity Recovery and Climate Experiment (GRACE) onboard GPS observations and K band range rate measurements to achieve the precise orbit of GRACE satellite and monthly temporal gravity field solutions to degree and order 60 successfully. The most significant part of the GRACE mission is the precise K band ranging (KBR) system to measure the ranges between the twin satellites. We analyze the characteristics and the observation error of K band range rate measurements which is critical to recovering the earth gravity field. A nine-points sliding window of least-squares fitting method is put forward to preprocess K band range rate measurements. This method is applied to recover the gravity field model to study the influence on recovering the Earth gravity field model. The results showed that: (1) RMS of fitting residual has been improved from 0.235μm/s to 0.182μm/s by using the K band range rate measurements in 2007. The results demonstrate that this method can eliminate outliner of KBRR observation data effectively. (2) This method is applied to recover the gravity field model. Comparisons of the degree variance and the spatial distribution of time-varying signal demonstrate that our model is comparable with the other existing models, i.e., the Centre for Space Research RL05, Jet Propulsion Laboratory RL05, and GeoForschungsZentrum RL05a models. Our model is very close to those from other three models and with similar spatial patterns of signals. The results indicate the preprocessing method in this paper can be effectively applied to the recovery of the earth gravity field model.
Integrated atom detector based on field ionization near carbon nanotubes
Gruener, B.; Jag, M.; Stibor, A.; Visanescu, G.; Haeffner, M.; Kern, D.; Guenther, A.; Fortagh, J.
2009-12-15
We demonstrate an atom detector based on field ionization and subsequent ion counting. We make use of field enhancement near tips of carbon nanotubes to reach extreme electrostatic field values of up to 9x10{sup 9} V/m, which ionize ground-state rubidium atoms. The detector is based on a carpet of multiwall carbon nanotubes grown on a substrate and used for field ionization, and a channel electron multiplier used for ion counting. We measure the field enhancement at the tips of carbon nanotubes by field emission of electrons. We demonstrate the operation of the field ionization detector by counting atoms from a thermal beam of a rubidium dispenser source. By measuring the ionization rate of rubidium as a function of the applied detector voltage we identify the field ionization distance, which is below a few tens of nanometers in front of nanotube tips. We deduce from the experimental data that field ionization of rubidium near nanotube tips takes place on a time scale faster than 10{sup -10} s. This property is particularly interesting for the development of fast atom detectors suitable for measuring correlations in ultracold quantum gases. We also describe an application of the detector as partial pressure gauge.
A Property Restriction Based Knowledge Merging Method
NASA Astrophysics Data System (ADS)
Che, Haiyan; Chen, Wei; Feng, Tie; Zhang, Jiachen
Merging new instance knowledge extracted from the Web according to certain domain ontology into the knowledge base (KB for short) is essential for the knowledge management and should be processed carefully, since this may introduce redundant or contradictory knowledge, and the quality of the knowledge in the KB, which is very important for a knowledge-based system to provide users high quality services, will suffer from such "bad" knowledge. Advocates a property restriction based knowledge merging method, it can identify the equivalent instances, redundant or contradictory knowledge according to the property restrictions defined in the domain ontology and can consolidate the knowledge about equivalent instances and discard the redundancy and conflict to keep the KB compact and consistent. This knowledge merging method has been used in a semantic-based search engine project: CRAB and the effect is satisfactory.
Recommendation advertising method based on behavior retargeting
NASA Astrophysics Data System (ADS)
Zhao, Yao; YIN, Xin-Chun; CHEN, Zhi-Min
2011-10-01
Online advertising has become an important business in e-commerce. Ad recommended algorithms are the most critical part in recommendation systems. We propose a recommendation advertising method based on behavior retargeting which can avoid leakage click of advertising due to objective reasons and can observe the changes of the user's interest in time. Experiments show that our new method can have a significant effect and can be further to apply to online system.
Trace projection transformation: A new method for measurement of debris flow surface velocity fields
NASA Astrophysics Data System (ADS)
Yan, Yan; Cui, Peng; Guo, Xiaojun; Ge, Yonggang
2016-09-01
Spatiotemporal variation of velocity is important for debris flow dynamics. This paper presents a new method, the trace projection transformation, for accurate, non-contact measurement of a debris-flow surface velocity field based on a combination of dense optical flow and perspective projection transformation. The algorithm for interpreting and processing is implemented in C ++ and realized in Visual Studio 2012. The method allows quantitative analysis of flow motion through videos from various angles (camera positioned at the opposite direction of fluid motion). It yields the spatiotemporal distribution of surface velocity field at pixel level and thus provides a quantitative description of the surface processes. The trace projection transformation is superior to conventional measurement methods in that it obtains the full surface velocity field by computing the optical flow of all pixels. The result achieves a 90% accuracy of when comparing with the observed values. As a case study, the method is applied to the quantitative analysis of surface velocity field of a specific debris flow.
Coal Field Fire Fighting - Practiced methods, strategies and tactics
NASA Astrophysics Data System (ADS)
Wündrich, T.; Korten, A. A.; Barth, U. H.
2009-04-01
achieved. For an effective and efficient fire fighting optimal tactics are requiered and can be divided into four fundamental tactics to control fire hazards: - Defense (digging away the coal, so that the coal can not begin to burn; or forming a barrier, so that the fire can not reach the not burning coal), - Rescue the coal (coal mining of a not burning seam), - Attack (active and direct cooling of burning seam), - Retreat (only monitoring till self-extinction of a burning seam). The last one is used when a fire exceeds the organizational and/or technical scope of a mission. In other words, "to control a coal fire" does not automatically and in all situations mean "to extinguish a coal fire". Best-practice tactics or a combination of them can be selected for control of a particular coal fire. For the extinguishing works different extinguishing agents are available. They can be applied by different application techniques and varying distinctive operating expenses. One application method may be the drilling of boreholes from the surface or covering the surface with low permeability soils. The mainly used extinction agents for coal field fire are as followed: Water (with or without additives), Slurry, Foaming mud/slurry, Inert gases, Dry chemicals and materials and Cryogenic agents. Because of its tremendous dimension and its complexity the worldwide challenge of coal fires is absolutely unique - it can only be solved with functional application methods, best fitting strategies and tactics, organisation and research as well as the dedication of the involved fire fighters, who work under extreme individual risks on the burning coal fields.
Using Problem Fields as a Method of Change.
ERIC Educational Resources Information Center
Pehkonen, Erkki
1992-01-01
Discusses the rationale and use of problem fields which are sets of related and/or connected open-ended problem-solving tasks within mathematics instruction. Polygons with matchsticks and the number triangle are two examples of problem fields presented along with variations in conditions that promote other matchstick puzzles. (11 references) (JJK)
Model based iterative reconstruction for Bright Field electron tomography
NASA Astrophysics Data System (ADS)
Venkatakrishnan, Singanallur V.; Drummy, Lawrence F.; De Graef, Marc; Simmons, Jeff P.; Bouman, Charles A.
2013-02-01
Bright Field (BF) electron tomography (ET) has been widely used in the life sciences to characterize biological specimens in 3D. While BF-ET is the dominant modality in the life sciences it has been generally avoided in the physical sciences due to anomalous measurements in the data due to a phenomenon called "Bragg scatter" - visible when crystalline samples are imaged. These measurements cause undesirable artifacts in the reconstruction when the typical algorithms such as Filtered Back Projection (FBP) and Simultaneous Iterative Reconstruction Technique (SIRT) are applied to the data. Model based iterative reconstruction (MBIR) provides a powerful framework for tomographic reconstruction that incorporates a model for data acquisition, noise in the measurement and a model for the object to obtain reconstructions that are qualitatively superior and quantitatively accurate. In this paper we present a novel MBIR algorithm for BF-ET which accounts for the presence of anomalous measurements from Bragg scatter in the data during the iterative reconstruction. Our method accounts for the anomalies by formulating the reconstruction as minimizing a cost function which rejects measurements that deviate significantly from the typical Beer's law model widely assumed for BF-ET. Results on simulated as well as real data show that our method can dramatically improve the reconstructions compared to FBP and MBIR without anomaly rejection, suppressing the artifacts due to the Bragg anomalies.
Tail Lobe Revisited: Magnetic Field Modeling Based on Plasma Data
NASA Technical Reports Server (NTRS)
Karlsson, S. B. P.; Tsyganenko, N. A.
1999-01-01
Plasma data from the ISEE-1 and -2 spacecraft during 1977-1980 have been used to determine the distribution of data points in the magnetotail in the range of distances -20 < XGSM < --15, i.e. which of the records that were located in the current sheet, in the tail lobe, in the magnetosheath and in the boundary layers respectively. The ISEE-1 and -2 magnetic field data for the records in the tail lobe were then used to model the tail lobe magnetic field dependence on the solar wind dynamic pressure, on the Interplanetary Magnetic Field (IMF) and on the Dst index. The tail lobe magnetic field was assumed to be dependent on the square root of the dynamic pressure based on the balance between the total magnetic pressure in the tail lobes and the dynamic pressure of the solar wind. The IMF dependent terms, added to the pressure term, were sought in many different forms while the Dst dependence of the tail lobe magnetic field was assumed to be linear. The field shows a strong dependence on the square root of the dynamic pressure and the different IMF dependent terms all constitute a significant contribution to the total field. However, the dependence on the Dst index turned out to be very weak at those down-tail distances. The results of this study are intended to be used for parameterizing future versions of the data-based models of the global magnetospheric magnetic field.
Geophysics-based method of locating a stationary earth object
Daily, Michael R.; Rohde, Steven B.; Novak, James L.
2008-05-20
A geophysics-based method for determining the position of a stationary earth object uses the periodic changes in the gravity vector of the earth caused by the sun- and moon-orbits. Because the local gravity field is highly irregular over a global scale, a model of local tidal accelerations can be compared to actual accelerometer measurements to determine the latitude and longitude of the stationary object.
Advanced materials characterization based on full field deformation measurements
NASA Astrophysics Data System (ADS)
Carpentier, A. Paige
Accurate stress-strain constitutive properties are essential for understanding the complex deformation and failure mechanisms for materials with highly anisotropic mechanical properties. Among such materials, glass-fiber- and carbon-fiber-reinforced polymer--matrix composites play a critical role in advanced structural designs. The large number of different methods and specimen types currently required to generate three-dimensional allowables for structural design slows down the material characterization. Also, some of the material constitutive properties are never measured due to the prohibitive cost of the specimens needed. This work shows that simple short-beam shear (SBS) specimens are well-suited for measurement of multiple constitutive properties for composite materials and that can enable a major shift toward accurate material characterization. The material characterization is based on the digital image correlation (DIC) full-field deformation measurement. The full-field-deformation measurement enables additional flexibility for assessment of stress--strain relations, compared to the conventional strain gages. Complex strain distributions, including strong gradients, can be captured. Such flexibility enables simpler test-specimen design and reduces the number of different specimen types required for assessment of stress--strain constitutive behavior. Two key elements show advantage of using DIC in the SBS tests. First, tensile, compressive, and shear stress--strain relations are measured in a single experiment. Second, a counter-intuitive feasibility of closed-form stress and modulus models, normally applicable to long beams, is demonstrated for short-beam specimens. The modulus and stress--strain data are presented for glass/epoxy and carbon/epoxy material systems. The applicability of the developed method to static, fatigue, and impact load rates is also demonstrated. In a practical method to determine stress-strain constitutive relations, the stress
Ultra-Sensitivity Glucose Sensor Based on Field Emitters
2009-01-01
A new glucose sensor based on field emitter of ZnO nanorod arrays (ZNA) was fabricated. This new type of ZNA field emitter-based sensor shows high sensitivity with experimental limit of detection of 1 nM glucose solution and a detection range from 1 nM to 50 μM in air at room temperature, which is lower than that of glucose sensors based on surface plasmon resonance spectroscopy, fluorescence signal transmission, and electrochemical signal transduction. The new glucose sensor provides a key technique for promising consuming application in biological system for detecting low levels of glucose on single cells or bacterial cultures. PMID:20596378
Bayesian individualization via sampling-based methods.
Wakefield, J
1996-02-01
We consider the situation where we wish to adjust the dosage regimen of a patient based on (in general) sparse concentration measurements taken on-line. A Bayesian decision theory approach is taken which requires the specification of an appropriate prior distribution and loss function. A simple method for obtaining samples from the posterior distribution of the pharmacokinetic parameters of the patient is described. In general, these samples are used to obtain a Monte Carlo estimate of the expected loss which is then minimized with respect to the dosage regimen. Some special cases which yield analytic solutions are described. When the prior distribution is based on a population analysis then a method of accounting for the uncertainty in the population parameters is described. Two simulation studies showing how the methods work in practice are presented. PMID:8827585
Fast and stable explicit operator splitting methods for phase-field models
NASA Astrophysics Data System (ADS)
Cheng, Yuanzhen; Kurganov, Alexander; Qu, Zhuolin; Tang, Tao
2015-12-01
Numerical simulations of phase-field models require long time computations and therefore it is necessary to develop efficient and highly accurate numerical methods. In this paper, we propose fast and stable explicit operator splitting methods for both one- and two-dimensional nonlinear diffusion equations for thin film epitaxy with slope selection and the Cahn-Hilliard equation. The equations are split into nonlinear and linear parts. The nonlinear part is solved using a method of lines together with an efficient large stability domain explicit ODE solver. The linear part is solved by a pseudo-spectral method, which is based on the exact solution and thus has no stability restriction on the time-step size. We demonstrate the performance of the proposed methods on a number of one- and two-dimensional numerical examples, where different stages of coarsening such as the initial preparation, alternating rapid structural transition and slow motion can be clearly observed.
NASA Astrophysics Data System (ADS)
Plaschke, F.; Glassmeier, K.-H.; Constantinescu, O. D.; Mann, I. R.; Milling, D. K.; Motschmann, U.; Rae, I. J.
2008-11-01
In this paper we introduce the field line resonance detector (FLRD), a wave telescope technique which has been specially adapted to estimate the spectral energy density of field line resonance (FLR) phase structures in a superposed wave field. The field line resonance detector is able to detect and correctly characterize several superposed FLR structures of a wave field and therefore constitutes a new and powerful tool in ULF pulsation studies. In our work we derive the technique from the classical wave telescope beamformer and present a statistical analysis of one year of ground based magnetometer data from the Canadian magnetometer network CANOPUS, now known as CARISMA. The statistical analysis shows that the FLRD is capable of detecting and characterizing superposed or hidden FLR structures in most of the detected ULF pulsation events; the one year statistical database is therefore extraordinarily comprehensive. The results of this analysis confirm the results of previous FLR characterizations and furthermore allow a detailed generalized dispersion analysis of FLRs.
[DNA-based methods for identification of seafood species].
Zhang, Li; Zhang, Liang; Liu, Shu-Cheng; Zhang, Yi-Jun; Han, Yi
2010-06-01
With the development of molecular biotechnology, methods for identification of seafood species are developed from protein to DNA. At present, the main DNA-based methods for species identification are FINS, PCR-RFLP, and specific-PCR, which have been used to identify the species of fresh, frozen, and pickled or canned seafood. However, qualitative and quantitative methods for identification of the mixed seafood species remain to be resolved. The gene databases play an important role in identifying species and are valuable information resources for identification of seafood species. In this paper, recent progresses of major DNA-based methods for identification of seafood species are reviewed and the perspectives of this field are discussed. PMID:20566458
A New Method and a New Scaling for Deriving Fermionic Mean-Field Dynamics
NASA Astrophysics Data System (ADS)
Petrat, Sören; Pickl, Peter
2016-03-01
We introduce a new method for deriving the time-dependent Hartree or Hartree-Fock equations as an effective mean-field dynamics from the microscopic Schrödinger equation for fermionic many-particle systems in quantum mechanics. The method is an adaption of the method used in Pickl (Lett. Math. Phys. 97 (2) 151-164 2011) for bosonic systems to fermionic systems. It is based on a Gronwall type estimate for a suitable measure of distance between the microscopic solution and an antisymmetrized product state. We use this method to treat a new mean-field limit for fermions with long-range interactions in a large volume. Some of our results hold for singular attractive or repulsive interactions. We can also treat Coulomb interaction assuming either a mild singularity cutoff or certain regularity conditions on the solutions to the Hartree(-Fock) equations. In the considered limit, the kinetic and interaction energy are of the same order, while the average force is subleading. For some interactions, we prove that the Hartree(-Fock) dynamics is a more accurate approximation than a simpler dynamics that one would expect from the subleading force. With our method we also treat the mean-field limit coupled to a semiclassical limit, which was discussed in the literature before, and we recover some of the previous results. All results hold for initial data close (but not necessarily equal) to antisymmetrized product states and we always provide explicit rates of convergence.
Adaptive integral method with fast Gaussian gridding for solving combined field integral equations
NASA Astrophysics Data System (ADS)
Bakır, O.; Baǧ; Cı, H.; Michielssen, E.
Fast Gaussian gridding (FGG), a recently proposed nonuniform fast Fourier transform algorithm, is used to reduce the memory requirements of the adaptive integral method (AIM) for accelerating the method of moments-based solution of combined field integral equations pertinent to the analysis of scattering from three-dimensional perfect electrically conducting surfaces. Numerical results that demonstrate the efficiency and accuracy of the AIM-FGG hybrid in comparison to an AIM-accelerated solver, which uses moment matching to project surface sources onto an auxiliary grid, are presented.
Detection of Inorganic Arsenic in Rice Using a Field Test Kit: A Screening Method.
Bralatei, Edi; Lacan, Severine; Krupp, Eva M; Feldmann, Jörg
2015-11-17
Rice is a staple food eaten by more than 50% of the world's population and is a daily dietary constituent in most South East Asian countries where 70% of the rice export comes from and where there is a high level of arsenic contamination in groundwater used for irrigation. Research shows that rice can take up and store inorganic arsenic during cultivation, and rice is considered to be one of the major routes of exposure to inorganic arsenic, a class I carcinogen for humans. Here, we report the use of a screening method based on the Gutzeit methodology to detect inorganic arsenic (iAs) in rice within 1 h. After optimization, 30 rice commodities from the United Kingdom market were tested with the field method and were compared to the reference method (high-performance liquid chromatography-inductively coupled plasma-mass spectrometry, HPLC-ICP-MS). In all but three rice samples, iAs compound can be determined. The results show no bias for iAs using the field method. Results obtained show quantification limits of about 50 μg kg(-1), a good reproducibility for a field method of ±12%, and only a few false positives and negatives (<10%) could only be recorded at the 2015 European Commission (EC) guideline for baby rice of 100 μg kg(-1), while none were recorded at the maximum level suggested by the World Health Organization (WHO) and implemented by the EC for polished and white rice of 200 μg kg(-1). The method is reliable, fast, and inexpensive; hence, it is suggested to be used as a screening method in the field for preselection of rice which violates legislative guidelines.
Alternative Methods for Field Corrections in Helical Solenoids
Lopes, M. L.; Krave, S. T.; Tompkins, J. C.; Yonehara, K.; Flanagan, G.; Kahn, S. A.; Melconian, K.
2015-05-01
Helical cooling channels have been proposed for highly efficient 6D muon cooling. Helical solenoids produce solenoidal, helical dipole, and helical gradient field components. Previous studies explored the geometric tunability limits on these main field components. In this paper we present two alternative correction schemes, tilting the solenoids and the addition of helical lines, to reduce the required strength of the anti-solenoid and add an additional tuning knob.
ERIC Educational Resources Information Center
Flores, Ingrid M.
2015-01-01
Thirty preservice teachers enrolled in a field-based science methods course were placed at a public elementary school for coursework and for teaching practice with elementary students. Candidates focused on building conceptual understanding of science content and pedagogical methods through innovative curriculum development and other course…
Enzyme catalysis enhanced dark-field imaging as a novel immunohistochemical method
NASA Astrophysics Data System (ADS)
Fan, Lin; Tian, Yanyan; Yin, Rong; Lou, Doudou; Zhang, Xizhi; Wang, Meng; Ma, Ming; Luo, Shouhua; Li, Suyi; Gu, Ning; Zhang, Yu
2016-04-01
Conventional immunohistochemistry is limited to subjective judgment based on human experience and thus it is clinically required to develop a quantitative immunohistochemical detection. 3,3'-Diaminobenzidin (DAB) aggregates, a type of staining product formed by conventional immunohistochemistry, were found to have a special optical property of dark-field imaging for the first time, and the mechanism was explored. On this basis, a novel immunohistochemical method based on dark-field imaging for detecting HER2 overexpressed in breast cancer was established, and the quantitative analysis standard and relevant software for measuring the scattering intensity was developed. In order to achieve a more sensitive detection, the HRP (horseradish peroxidase)-labeled secondary antibodies conjugated gold nanoparticles were constructed as nanoprobes to load more HRP enzymes, resulting in an enhanced DAB deposition as a dark-field label. Simultaneously, gold nanoparticles also act as a synergistically enhanced agent due to their mimicry of enzyme catalysis and dark-field scattering properties.Conventional immunohistochemistry is limited to subjective judgment based on human experience and thus it is clinically required to develop a quantitative immunohistochemical detection. 3,3'-Diaminobenzidin (DAB) aggregates, a type of staining product formed by conventional immunohistochemistry, were found to have a special optical property of dark-field imaging for the first time, and the mechanism was explored. On this basis, a novel immunohistochemical method based on dark-field imaging for detecting HER2 overexpressed in breast cancer was established, and the quantitative analysis standard and relevant software for measuring the scattering intensity was developed. In order to achieve a more sensitive detection, the HRP (horseradish peroxidase)-labeled secondary antibodies conjugated gold nanoparticles were constructed as nanoprobes to load more HRP enzymes, resulting in an enhanced DAB
Methner, M.M.; Bowman, J.D.
1998-03-01
Recent epidemiologic research has suggested that exposure to extremely low frequency (ELF) magnetic fields (MF) may be associated with leukemia, brain cancer, spontaneous abortions, and Alzheimer`s disease. A walkaround sampling method for measuring ambient ELF-MF levels was developed for use in conducting occupational hazard surveillance. This survey was designed to determine the range of MF levels at different industrial facilities so they could be categorized by MF levels and identified for possible subsequent personal exposure assessments. Industries were selected based on their annual electric power consumption in accordance with the hypothesis that large power consumers would have higher ambient MFs when compared with lower power consumers. Sixty-two facilities within thirteen 2-digit Standard Industrial Classifications (SIC) were selected based on their willingness to participate. A traditional industrial hygiene walkaround survey was conducted to identify MF sources, with a special emphasis on work stations.
UAV path planning using artificial potential field method updated by optimal control theory
NASA Astrophysics Data System (ADS)
Chen, Yong-bo; Luo, Guan-chen; Mei, Yue-song; Yu, Jian-qiao; Su, Xiao-long
2016-04-01
The unmanned aerial vehicle (UAV) path planning problem is an important assignment in the UAV mission planning. Based on the artificial potential field (APF) UAV path planning method, it is reconstructed into the constrained optimisation problem by introducing an additional control force. The constrained optimisation problem is translated into the unconstrained optimisation problem with the help of slack variables in this paper. The functional optimisation method is applied to reform this problem into an optimal control problem. The whole transformation process is deduced in detail, based on a discrete UAV dynamic model. Then, the path planning problem is solved with the help of the optimal control method. The path following process based on the six degrees of freedom simulation model of the quadrotor helicopters is introduced to verify the practicability of this method. Finally, the simulation results show that the improved method is more effective in planning path. In the planning space, the length of the calculated path is shorter and smoother than that using traditional APF method. In addition, the improved method can solve the dead point problem effectively.
Field-Based Teacher Education in Literacy: Preparing Teachers in Real Classroom Contexts
ERIC Educational Resources Information Center
DeGraff, Tricia L.; Schmidt, Cynthia M.; Waddell, Jennifer H.
2015-01-01
For the past two decades, scholars have advocated for reforms in teacher education that emphasize relevant connections between theory and practice in university coursework and focus on clinical experiences. This paper is based on our experiences in designing and implementing an integrated literacy methods course in a field-based teacher education…
Magnetic Field Measurements Based on Terfenol Coated Photonic Crystal Fibers
Quintero, Sully M. M.; Martelli, Cicero; Braga, Arthur M. B.; Valente, Luiz C. G.; Kato, Carla C.
2011-01-01
A magnetic field sensor based on the integration of a high birefringence photonic crystal fiber and a composite material made of Terfenol particles and an epoxy resin is proposed. An in-fiber modal interferometer is assembled by evenly exciting both eigenemodes of the HiBi fiber. Changes in the cavity length as well as the effective refractive index are induced by exposing the sensor head to magnetic fields. The magnetic field sensor has a sensitivity of 0.006 (nm/mT) over a range from 0 to 300 mT with a resolution about ±1 mT. A fiber Bragg grating magnetic field sensor is also fabricated and employed to characterize the response of Terfenol composite to the magnetic field. PMID:22247655
Magnetic field measurements based on Terfenol coated photonic crystal fibers.
Quintero, Sully M M; Martelli, Cicero; Braga, Arthur M B; Valente, Luiz C G; Kato, Carla C
2011-01-01
A magnetic field sensor based on the integration of a high birefringence photonic crystal fiber and a composite material made of Terfenol particles and an epoxy resin is proposed. An in-fiber modal interferometer is assembled by evenly exciting both eigenemodes of the HiBi fiber. Changes in the cavity length as well as the effective refractive index are induced by exposing the sensor head to magnetic fields. The magnetic field sensor has a sensitivity of 0.006 (nm/mT) over a range from 0 to 300 mT with a resolution about ±1 mT. A fiber Bragg grating magnetic field sensor is also fabricated and employed to characterize the response of Terfenol composite to the magnetic field.
NASA Technical Reports Server (NTRS)
Lyon, Richard G. (Inventor); Leisawitz, David T. (Inventor); Rinehart, Stephen A. (Inventor); Memarsadeghi, Nargess (Inventor)
2012-01-01
Disclosed herein are systems, computer-implemented methods, and tangible computer-readable storage media for wide field imaging interferometry. The method includes for each point in a two dimensional detector array over a field of view of an image: gathering a first interferogram from a first detector and a second interferogram from a second detector, modulating a path-length for a signal from an image associated with the first interferogram in the first detector, overlaying first data from the modulated first detector and second data from the second detector, and tracking the modulating at every point in a two dimensional detector array comprising the first detector and the second detector over a field of view for the image. The method then generates a wide-field data cube based on the overlaid first data and second data for each point. The method can generate an image from the wide-field data cube.
NASA Astrophysics Data System (ADS)
Lu, Wenbo; Jiang, Weikang; Yuan, Guoqing; Yan, Li
2013-05-01
Vibration signal analysis is the main technique in machine condition monitoring or fault diagnosis, whereas in some cases vibration-based diagnosis is restrained because of its contact measurement. Acoustic-based diagnosis (ABD) with non-contact measurement has received little attention, although sound field may contain abundant information related to fault pattern. A new scheme of ABD for gearbox based on near-field acoustic holography (NAH) and spatial distribution features of sound field is presented in this paper. It focuses on applying distribution information of sound field to gearbox fault diagnosis. A two-stage industrial helical gearbox is experimentally studied in a semi-anechoic chamber and a lab workshop, respectively. Firstly, multi-class faults (mild pitting, moderate pitting, severe pitting and tooth breakage) are simulated, respectively. Secondly, sound fields and corresponding acoustic images in different gearbox running conditions are obtained by fast Fourier transform (FFT) based NAH. Thirdly, by introducing texture analysis to fault diagnosis, spatial distribution features are extracted from acoustic images for capturing fault patterns underlying the sound field. Finally, the features are fed into multi-class support vector machine for fault pattern identification. The feasibility and effectiveness of our proposed scheme is demonstrated on the good experimental results and the comparison with traditional ABD method. Even with strong noise interference, spatial distribution features of sound field can reliably reveal the fault patterns of gearbox, and thus the satisfactory accuracy can be obtained. The combination of histogram features and gray level gradient co-occurrence matrix features is suggested for good diagnosis accuracy and low time cost.
Puurtinen, Merja; Viik, Jari; Takano, Noriyuki; Malmivuo, Jaakko; Hyttinen, Jari
2009-05-01
New portable electrocardiogram (ECG) measurement systems are emerging into market. Some use nonstandard bipolar electrode montage and sometimes very small interelectrode distances to improve the usability of the system. Modeling could provide a straightforward method to test new electrode systems. The aim of this study was to assess whether modeling the electrodes' measuring sensitivity with lead field method can provide a simple tool for testing a number of new electrode locations. We evaluated whether the actual ECG signal strength can be estimated by lead fields with two realistic 3D finite difference method (FDM) thorax models. We compared the modeling results to clinical body surface potential map (BSPM) data from 236 normal patients and studied 117 unipolar and 42 bipolar leads. In the case of unipolar electrodes the modeled measuring sensitivities correlated well with the clinical data (r=0.86, N=117, p<0.05). In the case of bipolar electrodes the correlation was moderate (r=0.62 between Model 1 and clinical data, r=0.71 between Model 2 and clinical data, N=42 and p<0.05 for both). Based on this we can conclude that lead field analysis based on realistic thorax models provides a good initial prediction for designing new electrode montages and measurement systems.
A new method for calculating the scattered field by an arbitrary cross-sectional conducting cylinder
NASA Astrophysics Data System (ADS)
Ragheb, Hassan A.
2011-04-01
Scattering of a plane electromagnetic wave by an arbitrary cross-sectional perfectly conducting cylinder must be performed numerically. This article aims to present a new approach for addressing this problem, which is based on simulating the arbitrary cross-sectional perfectly conducting cylinder by perfectly conducting strips of narrow width. The problem is then turned out to calculate the scattered electromagnetic field from N conducting strips. The technique of solving such a problem uses an asymptotic method. This method is based on an approximate technique introduced by Karp and Russek (Karp, S.N., and Russek, A. (1956), 'Diffraction by a Wide Slit', Journal of Applied Physics, 27, 886-894.) for solving scattering by wide slit. The method is applied here for calculating the scattered field in the far zone for E-polarised incident waves (transverse magnetic (TM) with respect to z-axis) on a perfectly conducting cylinder with arbitrary cross-section. Numerical examples are introduced first for comparison to show the accuracy of the method. Other examples for well-known scattering by conducting cylinders are then introduced followed by new examples which can only be solved by numerical methods.
Ray-based optical design tool for freeform optics: coma full-field display.
Bauer, Aaron; Rolland, Jannick P; Thompson, Kevin P
2016-01-11
The field of optical fabrication has progressed to a point where manufacturing optical quality freeform surfaces is no longer prohibitive. However, to stimulate the development of freeform systems, optical designers must be provided with the necessary tools. Full-field displays are an example of such a tool. Identifying the field dependence of the dominant aberrations of a freeform system is critical for a controlled optimization and with the help of full-field displays, this can be accomplished. Of specific interest is coma, an often system-limiting aberration and an aberration that has recently been directly addressed with freeform surfaces. In this research, we utilize nodal aberration theory to develop a ray-based method to generate a coma full-field display that circumvents wavefront fitting errors that can affect Zernike polynomial-based full-field displays for highly aberrated freeform starting designs.
A New Method for Radar Rainfall Estimation Using Merged Radar and Gauge Derived Fields
NASA Astrophysics Data System (ADS)
Hasan, M. M.; Sharma, A.; Johnson, F.; Mariethoz, G.; Seed, A.
2014-12-01
Accurate estimation of rainfall is critical for any hydrological analysis. The advantage of radar rainfall measurements is their ability to cover large areas. However, the uncertainties in the parameters of the power law, that links reflectivity to rainfall intensity, have to date precluded the widespread use of radars for quantitative rainfall estimates for hydrological studies. There is therefore considerable interest in methods that can combine the strengths of radar and gauge measurements by merging the two data sources. In this work, we propose two new developments to advance this area of research. The first contribution is a non-parametric radar rainfall estimation method (NPZR) which is based on kernel density estimation. Instead of using a traditional Z-R relationship, the NPZR accounts for the uncertainty in the relationship between reflectivity and rainfall intensity. More importantly, this uncertainty can vary for different values of reflectivity. The NPZR method reduces the Mean Square Error (MSE) of the estimated rainfall by 16 % compared to a traditionally fitted Z-R relation. Rainfall estimates are improved at 90% of the gauge locations when the method is applied to the densely gauged Sydney Terrey Hills radar region. A copula based spatial interpolation method (SIR) is used to estimate rainfall from gauge observations at the radar pixel locations. The gauge-based SIR estimates have low uncertainty in areas with good gauge density, whilst the NPZR method provides more reliable rainfall estimates than the SIR method, particularly in the areas of low gauge density. The second contribution of the work is to merge the radar rainfall field with spatially interpolated gauge rainfall estimates. The two rainfall fields are combined using a temporally and spatially varying weighting scheme that can account for the strengths of each method. The weight for each time period at each location is calculated based on the expected estimation error of each method
Characterizing the complex permittivity of high-κ dielectrics using enhanced field method
Chao, Hsien-Wen; Wong, Wei-Syuan; Chang, Tsun-Hsu
2015-11-15
This paper proposed a method to characterize the complex permittivities of samples based on the enhancement of the electric field strength. The enhanced field method significantly improves the measuring range and accuracy of the samples’ electrical properties. Full-wave simulations reveal that the resonant frequency is closely related to the dielectric constant of the sample. In addition, the loss tangent can be determined from the measured quality factor and the just obtained dielectric constant. Materials with low dielectric constant and very low loss tangent are measured for benchmarking and the measured results agree well with previous understanding. Interestingly, materials with extremely high dielectric constants (ε{sub r} > 50), such as titanium dioxide, calcium titanate, and strontium titanate, differ greatly as expected.
Characterizing the complex permittivity of high-κ dielectrics using enhanced field method.
Chao, Hsien-Wen; Wong, Wei-Syuan; Chang, Tsun-Hsu
2015-11-01
This paper proposed a method to characterize the complex permittivities of samples based on the enhancement of the electric field strength. The enhanced field method significantly improves the measuring range and accuracy of the samples' electrical properties. Full-wave simulations reveal that the resonant frequency is closely related to the dielectric constant of the sample. In addition, the loss tangent can be determined from the measured quality factor and the just obtained dielectric constant. Materials with low dielectric constant and very low loss tangent are measured for benchmarking and the measured results agree well with previous understanding. Interestingly, materials with extremely high dielectric constants (ε(r) > 50), such as titanium dioxide, calcium titanate, and strontium titanate, differ greatly as expected.
FIELD VALIDATION OF SEDIMENT TOXCITY IDENTIFCATION AND EVALUATION METHODS
Sediment Toxicity Identification and Evaluation (TIE) methods have been developed for both porewaters and whole sediments. These relatively simple laboratory methods are designed to identify specific toxicants or classes of toxicants in sediments; however, the question of whethe...
Method of using an electric field controlled emulsion phase contactor
Scott, Timothy C.
1993-01-01
A system for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity.
Method of using an electric field controlled emulsion phase contactor
Scott, T.C.
1993-11-16
A system is described for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity. 5 figures.
A phase match based frequency estimation method for sinusoidal signals
NASA Astrophysics Data System (ADS)
Shen, Yan-Lin; Tu, Ya-Qing; Chen, Lin-Jun; Shen, Ting-Ao
2015-04-01
Accurate frequency estimation affects the ranging precision of linear frequency modulated continuous wave (LFMCW) radars significantly. To improve the ranging precision of LFMCW radars, a phase match based frequency estimation method is proposed. To obtain frequency estimation, linear prediction property, autocorrelation, and cross correlation of sinusoidal signals are utilized. The analysis of computational complex shows that the computational load of the proposed method is smaller than those of two-stage autocorrelation (TSA) and maximum likelihood. Simulations and field experiments are performed to validate the proposed method, and the results demonstrate the proposed method has better performance in terms of frequency estimation precision than methods of Pisarenko harmonic decomposition, modified covariance, and TSA, which contribute to improving the precision of LFMCW radars effectively.
Tuning of random lasers by means of external magnetic fields based on the Voigt effect
NASA Astrophysics Data System (ADS)
Ghasempour Ardakani, Abbas; Mahdavi, Seyed Mohammad; Bahrampour, Ali Reza
2013-04-01
It has been proposed that emission spectrum of random lasers with magnetically active semiconductor constituents can be made tunable by external magnetic fields. By employing the FDTD method, the spectral intensity and spatial distribution of electric field are calculated in the presence of an external magnetic field. It is numerically shown that due to the magneto-optical Voigt effect, the emission spectrum of a semiconductor-based random laser can be made tunable by adjusting the external magnetic field. The effect of magnetic field on the localization length of the laser modes is investigated. It is also shown that the spatial distribution of electric field exhibited remarkable modification with variation of magnetic field.
Perspectives on the simulation of protein–surface interactions using empirical force field methods
Latour, Robert A.
2014-01-01
Protein–surface interactions are of fundamental importance for a broad range of applications in the fields of biomaterials and biotechnology. Present experimental methods are limited in their ability to provide a comprehensive depiction of these interactions at the atomistic level. In contrast, empirical force field based simulation methods inherently provide the ability to predict and visualize protein–surface interactions with full atomistic detail. These methods, however, must be carefully developed, validated, and properly applied before confidence can be placed in results from the simulations. In this perspectives paper, I provide an overview of the critical aspects that I consider being of greatest importance for the development of these methods, with a focus on the research that my combined experimental and molecular simulation groups have conducted over the past decade to address these issues. These critical issues include the tuning of interfacial force field parameters to accurately represent the thermodynamics of interfacial behavior, adequate sampling of these types of complex molecular systems to generate results that can be comparable with experimental data, and the generation of experimental data that can be used for simulation results evaluation and validation. PMID:25028242
Identifying work related injuries: comparison of methods for interrogating text fields
2010-01-01
Background Work-related injuries in Australia are estimated to cost around $57.5 billion annually, however there are currently insufficient surveillance data available to support an evidence-based public health response. Emergency departments (ED) in Australia are a potential source of information on work-related injuries though most ED's do not have an 'Activity Code' to identify work-related cases with information about the presenting problem recorded in a short free text field. This study compared methods for interrogating text fields for identifying work-related injuries presenting at emergency departments to inform approaches to surveillance of work-related injury. Methods Three approaches were used to interrogate an injury description text field to classify cases as work-related: keyword search, index search, and content analytic text mining. Sensitivity and specificity were examined by comparing cases flagged by each approach to cases coded with an Activity code during triage. Methods to improve the sensitivity and/or specificity of each approach were explored by adjusting the classification techniques within each broad approach. Results The basic keyword search detected 58% of cases (Specificity 0.99), an index search detected 62% of cases (Specificity 0.87), and the content analytic text mining (using adjusted probabilities) approach detected 77% of cases (Specificity 0.95). Conclusions The findings of this study provide strong support for continued development of text searching methods to obtain information from routine emergency department data, to improve the capacity for comprehensive injury surveillance. PMID:20374657
Polarization-current-based, finite-difference time-domain, near-to-far-field transformation.
Zeng, Yong; Moloney, Jerome V
2009-05-15
A near-to-far-field transformation algorithm for three-dimensional finite-difference time-domain is presented in this Letter. This approach is based directly on the polarization current of the scatterer, not the scattered near fields. It therefore eliminates the numerical errors originating from the spatial offset of the E and H fields, inherent in the standard near-to-far-field transformation. The proposed method is validated via direct comparisons with the analytical Lorentz-Mie solutions of plane waves scattered by large dielectric and metallic spheres with strong forward-scattering lobes. PMID:19448834
Intra-field overlay correction for illumination based distortion
NASA Astrophysics Data System (ADS)
Pike, Michael; Brunner, Timothy; Morgenfeld, Bradley; Jing, Nan; Wiltshire, Timothy
2015-03-01
The use of extreme freeform illumination conditions and multi patterning processes used to generate sub 40nm images can result in significant intra-field overlay errors. When levels with differing illumination conditions are aligned to each other, these intra-field distortions can result in overlay errors which are uncorrectable using normal linear feedback corrections. We use a double exposure method, previously described by Minghetti [1] et al. to isolate and measure intra-field overlay distortions caused by tool lens signatures and different illumination conditions. A full field test reticle is used to create a dual level expose pattern. The same pattern is exposed twice, but with two different illumination conditions. The first exposure is done with a standard reference illumination. The second exposure is the target illumination condition. The test reticle has overlay target pairs that are measurable when the 2nd exposure is offset in the Y direction by the designed amount. This allows for a high density, 13x13, intra-field overlay measurement to be collected and modeled to determine 2nd and 3rd order intra-field terms. Since the resulting illumination and scanner lens specific intra field corrections are independent of field size, the sub-recipes can be applied to any product exposure independent of field size, which use the same illumination conditions as the test exposures. When the method is applied to all exposure levels in a product build cycle, the overlay errors contributed by the reference illumination condition cancel out. The remaining errors are due exclusively to the impact of the illumination condition on that scanner lens. Actual results correlated well with the model with more than 80% of the predicted overlay improvement being achieved.
Occupation numbers of spherical orbits in self-consistent beyond-mean-field methods
NASA Astrophysics Data System (ADS)
Rodríguez, Tomás R.; Poves, Alfredo; Nowacki, Frédéric
2016-05-01
We present a method to compute the number of particles occupying spherical single-particle (SSP) levels within the energy density functional (EDF) framework. These SSP levels are defined for each nucleus by performing self-consistent mean-field calculations. The nuclear many-body states, in which the occupation numbers are evaluated, are obtained with a symmetry conserving configuration mixing (SCCM) method based on the Gogny EDF. The method allows a closer comparison between EDF and shell model with configuration mixing in large valence spaces (SM-CI) results, and can serve as a guidance to define physically sound valence spaces for SM-CI calculations. As a first application of the method, we analyze the onset of deformation in neutron-rich N =40 isotones and the role of the SSP levels around this harmonic oscillator magic number, with particular emphasis in the structure of 64Cr.
Enhancing Field Research Methods with Mobile Survey Technology
ERIC Educational Resources Information Center
Glass, Michael R.
2015-01-01
This paper assesses the experience of undergraduate students using mobile devices and a commercial application, iSurvey, to conduct a neighborhood survey. Mobile devices offer benefits for enhancing student learning and engagement. This field exercise created the opportunity for classroom discussions on the practicalities of urban research, the…
Field-structured material media and methods for synthesis thereof
Martin, James E.; Hughes, Robert C.; Anderson, Robert A.
2001-09-18
The present application is directed to a new class of composite materials, called field-structured composite (FSC) materials, which comprise a oriented aggregate structure made of magnetic particles suspended in a nonmagnetic medium, and to a new class of processes for their manufacture. FSC materials have much potential for application, including use in chemical, optical, environmental, and mechanical sensors.
NASA Astrophysics Data System (ADS)
Ido, Shunji; Hirose, Ryusuke
2001-12-01
A code using the 3-dimensional Finite Element Method (FEM) and Free Mesh Method (FMM) has been developed and applied to the magnetic field analyses in the plasma devices, where a ferromagnetic material is used as a target. An adaptive method is applied to the re-distribution of the nodes. It is shown that this method is useful in the magnetic field analyses.
A multicore based parallel image registration method.
Yang, Lin; Gong, Leiguang; Zhang, Hong; Nosher, John L; Foran, David J
2009-01-01
Image registration is a crucial step for many image-assisted clinical applications such as surgery planning and treatment evaluation. In this paper we proposed a landmark based nonlinear image registration algorithm for matching 2D image pairs. The algorithm was shown to be effective and robust under conditions of large deformations. In landmark based registration, the most important step is establishing the correspondence among the selected landmark points. This usually requires an extensive search which is often computationally expensive. We introduced a nonregular data partition algorithm using the K-means clustering algorithm to group the landmarks based on the number of available processing cores. The step optimizes the memory usage and data transfer. We have tested our method using IBM Cell Broadband Engine (Cell/B.E.) platform. PMID:19964921
Size-extensive vibrational self-consistent field methods with anharmonic geometry corrections
NASA Astrophysics Data System (ADS)
Hermes, Matthew R.; Keçeli, Murat; Hirata, So
2012-06-01
In the size-extensive vibrational self-consistent field (XVSCF) method introduced earlier [M. Keçeli and S. Hirata, J. Chem. Phys. 135, 134108 (2011)], 10.1063/1.3644895, only a small subset of even-order force constants that can form connected diagrams were used to compute extensive total energies and intensive transition frequencies. The mean-field potentials of XVSCF formed with these force constants have been shown to be effectively harmonic, making basis functions, quadrature, or matrix diagonalization in the conventional VSCF method unnecessary. We introduce two size-consistent VSCF methods, XVSCF(n) and XVSCF[n], for vibrationally averaged geometries in addition to energies and frequencies including anharmonic effects caused by up to the nth-order force constants. The methods are based on our observations that a small number of odd-order force constants of certain types can form open, connected diagrams isomorphic to the diagram of the mean-field potential gradients and that these nonzero gradients shift the potential minima by intensive amounts, which are interpreted as anharmonic geometry corrections. XVSCF(n) evaluates these mean-field gradients and force constants at the equilibrium geometry and estimates this shift accurately, but approximately, neglecting the coupling between these two quantities. XVSCF[n] solves the coupled equations for geometry corrections and frequencies with an iterative algorithm, giving results that should be identical to those of VSCF when applied to an infinite system. We present the diagrammatic and algebraic definitions, algorithms, and initial implementations as well as numerical results of these two methods. The results show that XVSCF(n) and XVSCF[n] reproduce the vibrationally averaged geometries of VSCF for naphthalene and anthracene in their ground and excited vibrational states accurately at fractions of the computational cost.
Field Instructors' Perceptions of Evidence-Based Practice in BSW Field Placement Sites
ERIC Educational Resources Information Center
Wiechelt, Shelly A.; Ting, Laura
2012-01-01
This exploratory study surveyed 17 BSW-level field instructors on their experience, beliefs, and perceived self-efficacy regarding evidence-based practice (EBP). The authors conducted focus groups concerning EBP in participants' agencies and with BSW students under their supervision. Results indicate that although they felt positive toward EBP and…
General purpose, field-portable cell-based biosensor platform.
Gilchrist, K H; Barker, V N; Fletcher, L E; DeBusschere, B D; Ghanouni, P; Giovangrandi, L; Kovacs, G T
2001-09-01
There are several groups of researchers developing cell-based biosensors for chemical and biological warfare agents based on electrophysiologic monitoring of cells. In order to transition such sensors from the laboratory to the field, a general-purpose hardware and software platform is required. This paper describes the design, implementation, and field-testing of such a system, consisting of cell-transport and data acquisition instruments. The cell-transport module is a self-contained, battery-powered instrument that allows various types of cell-based modules to be maintained at a preset temperature and ambient CO(2) level while in transit or in the field. The data acquisition module provides 32 channels of action potential amplification, filtering, and real-time data streaming to a laptop computer. At present, detailed analysis of the data acquired is carried out off-line, but sufficient computing power is available in the data acquisition module to enable the most useful algorithms to eventually be run real-time in the field. Both modules have sufficient internal power to permit realistic field-testing, such as the example presented in this paper. PMID:11544049
Random fields generation on the GPU with the spectral turning bands method
NASA Astrophysics Data System (ADS)
Hunger, L.; Cosenza, B.; Kimeswenger, S.; Fahringer, T.
2014-08-01
Random field (RF) generation algorithms are of paramount importance for many scientific domains, such as astrophysics, geostatistics, computer graphics and many others. Some examples are the generation of initial conditions for cosmological simulations or hydrodynamical turbulence driving. In the latter a new random field is needed every time-step. Current approaches commonly make use of 3D FFT (Fast Fourier Transform) and require the whole generated field to be stored in memory. Moreover, they are limited to regular rectilinear meshes and need an extra processing step to support non-regular meshes. In this paper, we introduce TBARF (Turning BAnd Random Fields), a RF generation algorithm based on the turning band method that is optimized for massively parallel hardware such as GPUs. Our algorithm replaces the 3D FFT with a lower order, one-dimensional FFT followed by a projection step, and is further optimized with loop unrolling and blocking. We show that TBARF can easily generate RF on non-regular (non uniform) meshes and can afford mesh sizes bigger than the available GPU memory by using a streaming, out-of-core approach. TBARF is 2 to 5 times faster than the traditional methods when generating RFs with more than 16M cells. It can also generate RF on non-regular meshes, and has been successfully applied to two real case scenarios: planetary nebulae and cosmological simulations.
Geometric and Topological Methods for Quantum Field Theory
NASA Astrophysics Data System (ADS)
Cardona, Alexander; Contreras, Iván.; Reyes-Lega, Andrés. F.
2013-05-01
Introduction; 1. A brief introduction to Dirac manifolds Henrique Bursztyn; 2. Differential geometry of holomorphic vector bundles on a curve Florent Schaffhauser; 3. Paths towards an extension of Chern-Weil calculus to a class of infinite dimensional vector bundles Sylvie Paycha; 4. Introduction to Feynman integrals Stefan Weinzierl; 5. Iterated integrals in quantum field theory Francis Brown; 6. Geometric issues in quantum field theory and string theory Luis J. Boya; 7. Geometric aspects of the standard model and the mysteries of matter Florian Scheck; 8. Absence of singular continuous spectrum for some geometric Laplacians Leonardo A. Cano García; 9. Models for formal groupoids Iván Contreras; 10. Elliptic PDEs and smoothness of weakly Einstein metrics of Hölder regularity Andrés Vargas; 11. Regularized traces and the index formula for manifolds with boundary Alexander Cardona and César Del Corral; Index.
Alternative methods to smooth the Earth's gravity field
NASA Technical Reports Server (NTRS)
Jekeli, C.
1981-01-01
Convolutions on the sphere with corresponding convolution theorems are developed for one and two dimensional functions. Some of these results are used in a study of isotropic smoothing operators or filters. Well known filters in Fourier spectral analysis, such as the rectangular, Gaussian, and Hanning filters, are adapted for data on a sphere. The low-pass filter most often used on gravity data is the rectangular (or Pellinen) filter. However, its spectrum has relatively large sidelobes; and therefore, this filter passes a considerable part of the upper end of the gravity spectrum. The spherical adaptations of the Gaussian and Hanning filters are more efficient in suppressing the high-frequency components of the gravity field since their frequency response functions are strongly field since their frequency response functions are strongly tapered at the high frequencies with no, or small, sidelobes. Formulas are given for practical implementation of these new filters.
Magnetic field adjustment structure and method for a tapered wiggler
Halbach, K.
1988-03-01
An improved wiggler having means for adjusting the magnetic field generated by electromagnet poles spaced along the path of a charged particle beam to compensate for energy losses in the charge particles is described which comprises; (a) windings on at least some of the electromagnet poles in the wiggler; (b) one of the windings on each of a group of adjacent electromagnet poles connected to a first power supply, and another winding on the electromagnet poles having more than one winding connected to a second power supply; and (c) means for independently adjusting one power supply to independently vary the current in one of the windings on a group of adjacent electromagnet poles; whereby the magnetic field strength of a group of adjacent electromagnet poles in the wiggler may be changed in smaller increments.
Gradient shimming based on regularized estimation for B0-field and shim functions.
Song, Kan; Bao, Qingjia; Chen, Fang; Huang, Chongyang; Feng, Jiwen; Liu, Chaoyang
2016-07-01
Mapping B0-field and shim functions spatially is a crucial step in the gradient shimming. The conventional estimation method used in the phase difference imaging technique takes no account for noise and T2(∗) effects, and is prone to create noisy and distorted field maps. This paper describes a new gradient shimming based on the regularized estimation for B0-field and shim functions. Based on a statistical model, the B0-field and shim function maps are estimated by a Penalized Maximum Likelihood method that minimizes two regularized least-squares cost functions, respectively. The first cost function of B0-field exploits the two facts that the noise in the phase difference measurements is Gaussian and the B0-field maps tend to be smooth. And the other one adds an additional fact that each shim function corresponds to a given spherical harmonic of the magnetic field. Significant improvements in the quality of field mapping and in the final shimming results are demonstrated through computer simulations as well as experiments, especially when the magnetic field homogeneity is poor. PMID:27131476
Gradient shimming based on regularized estimation for B0-field and shim functions
NASA Astrophysics Data System (ADS)
Song, Kan; Bao, Qingjia; Chen, Fang; Huang, Chongyang; Feng, Jiwen; Liu, Chaoyang
2016-07-01
Mapping B0-field and shim functions spatially is a crucial step in the gradient shimming. The conventional estimation method used in the phase difference imaging technique takes no account for noise and T2∗ effects, and is prone to create noisy and distorted field maps. This paper describes a new gradient shimming based on the regularized estimation for B0-field and shim functions. Based on a statistical model, the B0-field and shim function maps are estimated by a Penalized Maximum Likelihood method that minimizes two regularized least-squares cost functions, respectively. The first cost function of B0-field exploits the two facts that the noise in the phase difference measurements is Gaussian and the B0-field maps tend to be smooth. And the other one adds an additional fact that each shim function corresponds to a given spherical harmonic of the magnetic field. Significant improvements in the quality of field mapping and in the final shimming results are demonstrated through computer simulations as well as experiments, especially when the magnetic field homogeneity is poor.
Circuitry, systems and methods for detecting magnetic fields
Kotter, Dale K; Spencer, David F; Roybal, Lyle G; Rohrbaugh, David T
2010-09-14
Circuitry for detecting magnetic fields includes a first magnetoresistive sensor and a second magnetoresistive sensor configured to form a gradiometer. The circuitry includes a digital signal processor and a first feedback loop coupled between the first magnetoresistive sensor and the digital signal processor. A second feedback loop which is discrete from the first feedback loop is coupled between the second magnetoresistive sensor and the digital signal processor.
Computational Method for Electrical Potential and Other Field Problems
ERIC Educational Resources Information Center
Hastings, David A.
1975-01-01
Proposes the finite differences relaxation method as a teaching tool in secondary and university level courses discussing electrical potential, temperature distribution in a region, and similar problems. Outlines the theory and operating procedures of the method, and discusses examples of teaching applications, including possible laboratory…
PROGRESS ON GENERIC PHASE-FIELD METHOD DEVELOPMENT
Biner, Bullent; Tonks, Michael; Millett, Paul C.; Li, Yulan; Hu, Shenyang Y.; Gao, Fei; Sun, Xin; Martinez, E.; Anderson, D.
2012-09-26
In this report, we summarize our current collobarative efforts, involving three national laboratories: Idaho National Laboratory (INL), Pacific Northwest National Laboratory (PNNL) and Los Alamos National Laboatory (LANL), to develop a computational framework for homogenous and heterogenous nucleation mechanisms into the generic phase-field model. During the studies, the Fe-Cr system was chosen as a model system due to its simplicity and availability of reliable thermodynamic and kinetic data, as well as the range of applications of low-chromium ferritic steels in nuclear reactors. For homogenous nucleation, the relavant parameters determined from atomistic studies were used directly to determine the energy functional and parameters in the phase-field model. Interfacial energy, critical nucleus size, nucleation rate, and coarsening kinetics were systematically examined in two- and three- dimensional models. For the heteregoneous nucleation mechanism, we studied the nucleation and growth behavior of chromium precipitates due to the presence of dislocations. The results demonstrate that both nucleation schemes can be introduced to a phase-field modeling algorithm with the desired accuracy and computational efficiency.
Snyder, James W.; Hohenstein, Edward G.; Luehr, Nathan; Martínez, Todd J.
2015-10-21
We recently presented an algorithm for state-averaged complete active space self-consistent field (SA-CASSCF) orbital optimization that capitalizes on sparsity in the atomic orbital basis set to reduce the scaling of computational effort with respect to molecular size. Here, we extend those algorithms to calculate the analytic gradient and nonadiabatic coupling vectors for SA-CASSCF. Combining the low computational scaling with acceleration from graphical processing units allows us to perform SA-CASSCF geometry optimizations for molecules with more than 1000 atoms. The new approach will make minimal energy conical intersection searches and nonadiabatic dynamics routine for molecular systems with O(10{sup 2}) atoms.
Anisotropic Upper Critical Field of Iron-Based Superconductors
NASA Astrophysics Data System (ADS)
Huang, Ruiqi; She, Weilong
2016-09-01
The upper critical field and its anisotropy are the easiest properties to examine in the research of iron-based superconductors. Based on warped cylindrical Fermi surface models, we investigate the temperature and angle dependence of the upper critical field in detail by employing the quasi-classical formalism of the Werthamer-Helfand-Hohenberg (WHH) theory. Our numerical results reveal the anisotropy of the upper critical field, which may be caused by an anisotropic gap function (e.g., d-wave pairing) or an anisotropic Fermi surface, respectively. Further, according to our analysis, this anisotropy can be modulated by the deformation of the Fermi surface and will be strongly suppressed by the Pauli paramagnetic effect.
Ab Initio Force Fields for Imidazolium-Based Ionic Liquids.
McDaniel, Jesse G; Choi, Eunsong; Son, Chang Yun; Schmidt, J R; Yethiraj, Arun
2016-07-21
We develop ab initio force fields for alkylimidazolium-based ionic liquids (ILs) that predict the density, heats of vaporization, diffusion, and conductivity that are in semiquantitative agreement with experimental data. These predictions are useful in light of the scarcity of and sometimes inconsistency in experimental heats of vaporization and diffusion coefficients. We illuminate physical trends in the liquid cohesive energy with cation chain length and anion. These trends are different than those based on the experimental heats of vaporization. Molecular dynamics prediction of the room temperature dynamics of such ILs is more difficult than is generally realized in the literature due to large statistical uncertainties and sensitivity to subtle force field details. We believe that our developed force fields will be useful for correctly determining the physics responsible for the structure/property relationships in neat ILs.
Towards Making Data Bases Practical for use in the Field
NASA Astrophysics Data System (ADS)
Fischer, T. P.; Lehnert, K. A.; Chiodini, G.; McCormick, B.; Cardellini, C.; Clor, L. E.; Cottrell, E.
2014-12-01
Geological, geochemical, and geophysical research is often field based with travel to remote areas and collection of samples and data under challenging environmental conditions. Cross-disciplinary investigations would greatly benefit from near real-time data access and visualisation within the existing framework of databases and GIS tools. An example of complex, interdisciplinary field-based and data intensive investigations is that of volcanologists and gas geochemists, who sample gases from fumaroles, hot springs, dry gas vents, hydrothermal vents and wells. Compositions of volcanic gas plumes are measured directly or by remote sensing. Soil gas fluxes from volcanic areas are measured by accumulation chamber and involve hundreds of measurements to calculate the total emission of a region. Many investigators also collect rock samples from recent or ancient volcanic eruptions. Structural, geochronological, and geophysical data collected during the same or related field campaigns complement these emissions data. All samples and data collected in the field require a set of metadata including date, time, location, sample or measurement id, and descriptive comments. Currently, most of these metadata are written in field notebooks and later transferred into a digital format. Final results such as laboratory analyses of samples and calculated flux data are tabulated for plotting, correlation with other types of data, modeling and finally publication and presentation. Data handling, organization and interpretation could be greatly streamlined by using digital tools available in the field to record metadata, assign an International Geo Sample Number (IGSN), upload measurements directly from field instruments, and arrange sample curation. Available data display tools such as GeoMapApp and existing data sets (PetDB, IRIS, UNAVCO) could be integrated to direct locations for additional measurements during a field campaign. Nearly live display of sampling locations, pictures
Optimal grid-based methods for thin film micromagnetics simulations
NASA Astrophysics Data System (ADS)
Muratov, C. B.; Osipov, V. V.
2006-08-01
Thin film micromagnetics are a broad class of materials with many technological applications, primarily in magnetic memory. The dynamics of the magnetization distribution in these materials is traditionally modeled by the Landau-Lifshitz-Gilbert (LLG) equation. Numerical simulations of the LLG equation are complicated by the need to compute the stray field due to the inhomogeneities in the magnetization which presents the chief bottleneck for the simulation speed. Here, we introduce a new method for computing the stray field in a sample for a reduced model of ultra-thin film micromagnetics. The method uses a recently proposed idea of optimal finite difference grids for approximating Neumann-to-Dirichlet maps and has an advantage of being able to use non-uniform discretization in the film plane, as well as an efficient way of dealing with the boundary conditions at infinity for the stray field. We present several examples of the method's implementation and give a detailed comparison of its performance for studying domain wall structures compared to the conventional FFT-based methods.
NASA Astrophysics Data System (ADS)
Lin, M. C.; Loverich, J.; Stoltz, P. H.; Nieter, C.
2013-10-01
This work introduces a conformal finite difference time domain (CFDTD) particle-in-cell (PIC) method with an improved field emission algorithm to accurately and efficiently study field emission devices. The CFDTD method is based on the Dey-Mittra algorithm or cut-cell algorithm, as implemented in the Vorpal code. For the field emission algorithm, we employ the elliptic function v(y) found by Forbes and a new fitting function t(y)2 for the Fowler-Nordheim (FN) equation. With these improved correction factors, field emission of electrons from a cathode surface is much closer to the prediction of the exact FN formula derived by Murphy and Good. This work was supported in part by both the U.S. Department of Defense under Grant No. FA9451-07-C-0025 and the U.S. Department of Energy under Grant No. DE-SC0004436.
Participative Critical Enquiry in Graduate Field-Based Learning
ERIC Educational Resources Information Center
Reilly, Kathy; Clavin, Alma; Morrissey, John
2016-01-01
This paper outlines a critical pedagogic approach to field-based learning (FBL) at graduate level. Drawing on student experience stemming from a FBL module and as part of an MA programme in Environment, Society and Development, the paper addresses the complexities associated with student-led, participative critical enquiry during fieldwork in…
A Successful Field-Based Program at Mercer University.
ERIC Educational Resources Information Center
Peek, Patricia P.
The Mercer University field-based program in elementary education provides practical experience beginning in the junior year. The prospective teacher starts with observations in public school classrooms while enrolled in a foundations of education course. Opportunities to work directly with children commence in the second quarter of the junior…
A Collaborative Field-Based Urban Teacher Education Program.
ERIC Educational Resources Information Center
Guyton, Edith; And Others
1993-01-01
Describes a 12-month, field-based, alternative teacher preparation program for individuals holding baccalaureate degrees in areas outside education who want master's degrees in early childhood education. The program involves collaboration between the State Department of Education, the Early Childhood Department of an urban university, and four…
Field-Based Research Experience in Earth Science Teacher Education.
ERIC Educational Resources Information Center
O'Neal, Michael L.
2003-01-01
Describes the pilot of a field-based research experience in earth science teacher education designed to produce well-prepared, scientifically and technologically literate earth science teachers through a teaching- and research-oriented partnership between in-service teachers and a university scientist-educator. Indicates that the pilot program was…
Integrating Evidence-Based Practice and Social Work Field Education
ERIC Educational Resources Information Center
Edmond, Tonya; Megivern, Deborah; Williams, Cynthia; Rochman, Estelle; Howard, Matthew
2006-01-01
The social work academic community is currently considering and critiquing the idea of evidence-based practice (EBP). Given the vital part that practicum education plays in the social work profession, understanding the views of field instructors on this subject is essential. The George Warren Brown School of Social Work at Washington University…
Incorporating Technology in the Field-Based Preparation of Teachers.
ERIC Educational Resources Information Center
Brush, Thomas; And Others
1994-01-01
Describes a program at Indiana University that uses technology to establish off-campus links with public schools to offer field-based distance education to teachers. The use of audiographics, fax machines, teleconferencing, and enhanced electronic mail systems for collaboration and training is explained. (Contains 10 references.) (LRW)
Chapter 11. Community analysis-based methods
Cao, Y.; Wu, C.H.; Andersen, G.L.; Holden, P.A.
2010-05-01
Microbial communities are each a composite of populations whose presence and relative abundance in water or other environmental samples are a direct manifestation of environmental conditions, including the introduction of microbe-rich fecal material and factors promoting persistence of the microbes therein. As shown by culture-independent methods, different animal-host fecal microbial communities appear distinctive, suggesting that their community profiles can be used to differentiate fecal samples and to potentially reveal the presence of host fecal material in environmental waters. Cross-comparisons of microbial communities from different hosts also reveal relative abundances of genetic groups that can be used to distinguish sources. In increasing order of their information richness, several community analysis methods hold promise for MST applications: phospholipid fatty acid (PLFA) analysis, denaturing gradient gel electrophoresis (DGGE), terminal restriction fragment length polymorphism (TRFLP), cloning/sequencing, and PhyloChip. Specific case studies involving TRFLP and PhyloChip approaches demonstrate the ability of community-based analyses of contaminated waters to confirm a diagnosis of water quality based on host-specific marker(s). The success of community-based MST for comprehensively confirming fecal sources relies extensively upon using appropriate multivariate statistical approaches. While community-based MST is still under evaluation and development as a primary diagnostic tool, results presented herein demonstrate its promise. Coupled with its inherently comprehensive ability to capture an unprecedented amount of microbiological data that is relevant to water quality, the tools for microbial community analysis are increasingly accessible, and community-based approaches have unparalleled potential for translation into rapid, perhaps real-time, monitoring platforms.
Phase field method to optimize dielectric devices for electromagnetic wave propagation
NASA Astrophysics Data System (ADS)
Takezawa, Akihiro; Kitamura, Mitsuru
2014-01-01
We discuss a phase field method for shape optimization in the context of electromagnetic wave propagation. The proposed method has the same functional capabilities as the level set method for shape optimization. The first advantage of the method is the simplicity of computation, since extra operations such as re-initialization of functions are not required. The second is compatibility with the topology optimization method due to the similar domain representation and the sensitivity analysis. Structural shapes are represented by the phase field function defined in the design domain, and this function is optimized by solving a time-dependent reaction diffusion equation. The artificial double-well potential function used in the equation is derived from sensitivity analysis. We study four types of 2D or 2.5D (axisymmetric) optimization problems. Two are the classical problems of photonic crystal design based on the Bloch theory and photonic crystal wave guide design, and two are the recent topics of designing dielectric left-handed metamaterials and dielectric ring resonators.
Phase field method to optimize dielectric devices for electromagnetic wave propagation
Takezawa, Akihiro Kitamura, Mitsuru
2014-01-15
We discuss a phase field method for shape optimization in the context of electromagnetic wave propagation. The proposed method has the same functional capabilities as the level set method for shape optimization. The first advantage of the method is the simplicity of computation, since extra operations such as re-initialization of functions are not required. The second is compatibility with the topology optimization method due to the similar domain representation and the sensitivity analysis. Structural shapes are represented by the phase field function defined in the design domain, and this function is optimized by solving a time-dependent reaction diffusion equation. The artificial double-well potential function used in the equation is derived from sensitivity analysis. We study four types of 2D or 2.5D (axisymmetric) optimization problems. Two are the classical problems of photonic crystal design based on the Bloch theory and photonic crystal wave guide design, and two are the recent topics of designing dielectric left-handed metamaterials and dielectric ring resonators.
Measuring slope to improve energy expenditure estimates during field-based activities
Duncan, Glen E.; Lester, Jonathan; Migotsky, Sean; Higgins, Lisa; Borriello, Gaetano
2013-01-01
This technical note describes methods to improve activity energy expenditure estimates using a multi-sensor board (MSB) by measuring slope. Ten adults walked over a 2.5-mile course wearing an MSB and mobile calorimeter. Energy expenditure was estimated using accelerometry alone (base) and four methods to measure slope. The barometer and GPS methods improved accuracy 11% from the base (Ps < 0.05) to 86% overall. Measuring slope using the MSB improves energy expenditure estimates during field-based activities. PMID:23537030
Ionic solvation studied by image-charge reaction field method
Lin, Yuchun; Baumketner, Andrij; Song, Wei; Deng, Shaozhong; Jacobs, Donald; Cai, Wei
2011-01-01
In a preceding paper [J. Chem. Phys. 131, 154103 (2009)], we introduced a new, hybrid explicit∕implicit method to treat electrostatic interactions in computer simulations, and tested its performance for liquid water. In this paper, we report further tests of this method, termed the image-charge solvation model (ICSM), in simulations of ions solvated in water. We find that our model can faithfully reproduce known solvation properties of sodium and chloride ions. The charging free energy of a single sodium ion is in excellent agreement with the estimates by other electrostatics methods, while offering much lower finite-size errors. Similarly, the potentials of mean force computed for Na–Cl, Na–Na, and Cl–Cl pairs closely reproduce those reported previously. Collectively, our results demonstrate the superior accuracy of the proposed ICSM method for simulations of mixed media. PMID:21280685
Field sampling method for quantifying odorants in humid environments.
Trabue, Steven L; Scoggin, Kenwood D; Li, Hong; Burns, Robert; Xin, Hongwei
2008-05-15
Most air quality studies in agricultural environments use thermal desorption analysis for quantifying semivolatile organic compounds (SVOCs) associated with odor. The objective of this study was to develop a robust sampling technique for measuring SVOCs in humid environments. Test atmospheres were generated at ambient temperatures (23 +/- 1.5 degrees C) and 25, 50, and 80% relative humidity (RH). Sorbent material used included Tenax, graphitized carbon, and carbon molecular sieve (CMS). Sorbent tubes were challenged with 2, 4, 8, 12, and 24 L of air at various RHs. Sorbent tubes with CMS material performed poorly at both 50 and 80% RH dueto excessive sorption of water. Heating of CMS tubes during sampling or dry-purging of CMS tubes post sampling effectively reduced water sorption with heating of tubes being preferred due to the higher recovery and reproducibility. Tenaxtubes had breakthrough of the more volatile compounds and tended to form artifacts with increasing volumes of air sampled. Graphitized carbon sorbent tubes containing Carbopack X and Carbopack C performed best with quantitative recovery of all compounds at all RHs and sampling volumes tested. The graphitized carbon tubes were taken to the field for further testing. Field samples taken from inside swine feeding operations showed that butanoic acid, 4-methylphenol, 4-ethylphenol, indole, and 3-methylindole were the compounds detected most often above their odor threshold values. Field samples taken from a poultry facility demonstrated that butanoic acid, 3-methylbutanoic acid, and 4-methylphenol were the compounds above their odor threshold values detected most often, relative humidity, CAFO, VOC, SVOC, thermal desorption, swine, poultry, air quality, odor. PMID:18546717
Novel magnetic field sensor based on magnetic fluids infiltrated dual-core photonic crystal fibers
NASA Astrophysics Data System (ADS)
Li, Jianhua; Wang, Rong; Wang, Jingyuan; Zhang, Baofu; Xu, Zhiyong; Wang, Huali
2014-03-01
Novel magnetic field sensor based on magnetic fluids infiltrated dual-core Photonic Crystal Fibers (PCFs) is proposed in this paper. Inside the cross-section of the designed PCFs, the two fiber cores filled with magnetic fluids (Fe3O4) are separated by an air hole, and then form two independent waveguides with mode coupling. The mode coupling under different magnetic field strength is investigated theoretically. A novel and simple magnetic field sensing system is proposed and its sensing performances have been studied numerically. The results show that the magnetic field sensor with 15-cm PCFs has a large sensing range and high sensitivity of 4.80 pm/Oe. It provides a new feasible method to design PCF-based magnetic field sensor.
NASA Astrophysics Data System (ADS)
Gauthier, P.-A.; Camier, C.; Lebel, F.-A.; Pasco, Y.; Berry, A.; Langlois, J.; Verron, C.; Guastavino, C.
2016-08-01
Sound environment reproduction of various flight conditions in aircraft mock-ups is a valuable tool for the study, prediction, demonstration and jury testing of interior aircraft sound quality and annoyance. To provide a faithful reproduced sound environment, time, frequency and spatial characteristics should be preserved. Physical sound field reproduction methods for spatial sound reproduction are mandatory to immerse the listener's body in the proper sound fields so that localization cues are recreated at the listener's ears. Vehicle mock-ups pose specific problems for sound field reproduction. Confined spaces, needs for invisible sound sources and very specific acoustical environment make the use of open-loop sound field reproduction technologies such as wave field synthesis (based on free-field models of monopole sources) not ideal. In this paper, experiments in an aircraft mock-up with multichannel least-square methods and equalization are reported. The novelty is the actual implementation of sound field reproduction with 3180 transfer paths and trim panel reproduction sources in laboratory conditions with a synthetic target sound field. The paper presents objective evaluations of reproduced sound fields using various metrics as well as sound field extrapolation and sound field characterization.
A flocking based method for brain tractography.
Aranda, Ramon; Rivera, Mariano; Ramirez-Manzanares, Alonso
2014-04-01
We propose a new method to estimate axonal fiber pathways from Multiple Intra-Voxel Diffusion Orientations. Our method uses the multiple local orientation information for leading stochastic walks of particles. These stochastic particles are modeled with mass and thus they are subject to gravitational and inertial forces. As result, we obtain smooth, filtered and compact trajectory bundles. This gravitational interaction can be seen as a flocking behavior among particles that promotes better and robust axon fiber estimations because they use collective information to move. However, the stochastic walks may generate paths with low support (outliers), generally associated to incorrect brain connections. In order to eliminate the outlier pathways, we propose a filtering procedure based on principal component analysis and spectral clustering. The performance of the proposal is evaluated on Multiple Intra-Voxel Diffusion Orientations from two realistic numeric diffusion phantoms and a physical diffusion phantom. Additionally, we qualitatively demonstrate the performance on in vivo human brain data. PMID:24583805
Method for extruding pitch based foam
Klett, James W.
2002-01-01
A method and apparatus for extruding pitch based foam is disclosed. The method includes the steps of: forming a viscous pitch foam; passing the precursor through an extrusion tube; and subjecting the precursor in said extrusion tube to a temperature gradient which varies along the length of the extrusion tube to form an extruded carbon foam. The apparatus includes an extrusion tube having a passageway communicatively connected to a chamber in which a viscous pitch foam formed in the chamber paring through the extrusion tube, and a heating mechanism in thermal communication with the tube for heating the viscous pitch foam along the length of the tube in accordance with a predetermined temperature gradient.
Homogenization method based on the inverse problem
Tota, A.; Makai, M.
2013-07-01
We present a method for deriving homogeneous multi-group cross sections to replace a heterogeneous region's multi-group cross sections; providing that the fluxes and the currents on the external boundary, and the region averaged fluxes are preserved. The method is developed using diffusion approximation to the neutron transport equation in a symmetrical slab geometry. Assuming that the boundary fluxes are given, two response matrices (RMs) can be defined. The first derives the boundary current from the boundary flux, the second derives the flux integral over the region from the boundary flux. Assuming that these RMs are known, we present a formula which reconstructs the multi-group cross-section matrix and the diffusion coefficients from the RMs of a homogeneous slab. Applying this formula to the RMs of a slab with multiple homogeneous regions yields a homogenization method; which produce such homogenized multi-group cross sections and homogenized diffusion coefficients, that the fluxes and the currents on the external boundary, and the region averaged fluxes are preserved. The method is based on the determination of the eigenvalues and the eigenvectors of the RMs. We reproduce the four-group cross section matrix and the diffusion constants from the RMs in numerical examples. We give conditions for replacing a heterogeneous region by a homogeneous one so that the boundary current and the region-averaged flux are preserved for a given boundary flux. (authors)
Dreamlet-based interpolation using POCS method
NASA Astrophysics Data System (ADS)
Wang, Benfeng; Wu, Ru-Shan; Geng, Yu; Chen, Xiaohong
2014-10-01
Due to incomplete and non-uniform coverage of the acquisition system and dead traces, real seismic data always has some missing traces which affect the performance of a multi-channel algorithm, such as Surface-Related Multiple Elimination (SRME), imaging and inversion. Therefore, it is necessary to interpolate seismic data. Dreamlet transform has been successfully used in the modeling of seismic wave propagation and imaging, and this paper explains the application of dreamlet transform to seismic data interpolation. In order to avoid spatial aliasing in transform domain thus getting arbitrary under-sampling rate, improved Jittered under-sampling strategy is proposed to better control the dataset. With L0 constraint and Projection Onto Convex Sets (POCS) method, performances of dreamlet-based and curvelet-based interpolation are compared in terms of recovered signal to noise ratio (SNR) and convergence rate. Tests on synthetic and real cases demonstrate that dreamlet transform has superior performance to curvelet transform.
Geometric and Topological Methods for Quantum Field Theory
NASA Astrophysics Data System (ADS)
Ocampo, Hernan; Pariguan, Eddy; Paycha, Sylvie
2010-04-01
Introduction; 1. The impact of QFT on low-dimensional topology Paul Kirk; 2. Differential equations aspects of quantum cohomology Martin A. Guest; 3. Index theory and groupoids Claire Debord and Jean-Marie Lescure; 4. Renormalization Hopf algebras and combinatorial groups Alessandra Frabetti; 5. BRS invariance for massive boson fields José M. Gracia-Bondía; 6. Large N field theories and geometry David Berenstein; 7. Functional renormalization group equations, asymptotic safety, and quantum Einstein gravity Martin Reuter and Frank Saueressig; 8. When is a differentiable manifold the boundary of an orbifold? Andrés Angel; 9. Canonical group quantization, rotation generators and quantum indistinguishability Carlos Benavides and Andrés Reyes-Lega; 10. Conserved currents in Kähler manifolds Jaime R. Camacaro and Juan Carlos Moreno; 11. A symmetrized canonical determinant on odd-class pseudodifferential operators Marie-Françoise Ouedraogo; 12. Some remarks about cosymplectic metrics on maximal flag manifolds Marlio Paredes and Sofia Pinzón; 13. Heisenberg modules over real multiplication noncommutative tori and related algebraic structures Jorge Plazas; Index.
Field Analysis of Microbial Contamination Using Three Molecular Methods in Parallel
NASA Technical Reports Server (NTRS)
Morris, H.; Stimpson, E.; Schenk, A.; Kish, A.; Damon, M.; Monaco, L.; Wainwright, N.; Steele, A.
2010-01-01
Advanced technologies with the capability of detecting microbial contamination remain an integral tool for the next stage of space agency proposed exploration missions. To maintain a clean, operational spacecraft environment with minimal potential for forward contamination, such technology is a necessity, particularly, the ability to analyze samples near the point of collection and in real-time both for conducting biological scientific experiments and for performing routine monitoring operations. Multiple molecular methods for detecting microbial contamination are available, but many are either too large or not validated for use on spacecraft. Two methods, the adenosine- triphosphate (ATP) and Limulus Amebocyte Lysate (LAL) assays have been approved by the NASA Planetary Protection Office for the assessment of microbial contamination on spacecraft surfaces. We present the first parallel field analysis of microbial contamination pre- and post-cleaning using these two methods as well as universal primer-based polymerase chain reaction (PCR).
A field method for making a quantitative estimate of altered tuff in sandstone
Cadigan, R.A.
1954-01-01
The use of benzidine to identify altered tuff in sandstone is practical for field or field laboratory studies associated with stratigraphic correlations, mineral deposit investigations, or paleogeographic interpretations. The method is based on the ability of saturated benzidine (C12H12N2) solution to produce a blue stain on montmorillonite-bearing tuff grains. The method is substantiated by the results of microscopic, X-ray spectrometer, and spectrographic tests which lead to the conclusion that: (1) the benzidine stain test differentiates grains of different composition, (2) the white or gray grains which are stained a uniform blue color are fragments of altered tuff, and (3) white or gray grains which stain in a few small spots are probably silicified tuff. The amount of sand grains taken from a hand specimen or an outcrop which will be held by a penny is spread out on a nonabsorbent white surface and soaked with benzidine for 5 minutes. The approximate number blue grains and the average grain size are used in a chart to determine a reference number which measures relative order of abundance. The chart, based on a volume relationship, corrects for the variation in the number of grains in the sample as the grain size varies. Practical use of the method depends on a knowledge of several precautionary measures as well as an understanding of the limitations of benzidine staining tests.
Magnetic field sensor using a polymer-based vibrator
NASA Astrophysics Data System (ADS)
Wu, Jiang; Hasebe, Kazuhiko; Mizuno, Yosuke; Tabaru, Marie; Nakamura, Kentaro
2016-09-01
In this technical note, a polymer-based magnetic sensor with a high resolution was devised for sensing the high magnetic field. It consisted of a bimorph (vibrator) made of poly (phenylene sulfide) (PPS) and a phosphor-bronze foil glued on the free end of the bimorph. According to Faraday’s law of induction, when a magnetic field in the direction perpendicular to the bimorph was applied, the foil cut the magnetic flux, and generated an alternating voltage across the leads at the natural frequency of the bimorph. Because PPS has low mechanical loss, low elastic modulus, and low density, high vibration velocity can be achieved if it is employed as the elastomer of the bimorph. The devised sensor was tested in the magnetic field range of 0.1–570 mT and exhibited a minimum detectable magnetic field of 0.1 mT. At a zero-to-peak driving voltage of 60 V, the sensitivity of the PPS-based magnetic sensor reached 10.5 V T‑1, which was 1.36 times the value of the aluminum-based magnetic sensor with the same principle and dimensions.
Magnetic field sensor using a polymer-based vibrator
NASA Astrophysics Data System (ADS)
Wu, Jiang; Hasebe, Kazuhiko; Mizuno, Yosuke; Tabaru, Marie; Nakamura, Kentaro
2016-09-01
In this technical note, a polymer-based magnetic sensor with a high resolution was devised for sensing the high magnetic field. It consisted of a bimorph (vibrator) made of poly (phenylene sulfide) (PPS) and a phosphor-bronze foil glued on the free end of the bimorph. According to Faraday’s law of induction, when a magnetic field in the direction perpendicular to the bimorph was applied, the foil cut the magnetic flux, and generated an alternating voltage across the leads at the natural frequency of the bimorph. Because PPS has low mechanical loss, low elastic modulus, and low density, high vibration velocity can be achieved if it is employed as the elastomer of the bimorph. The devised sensor was tested in the magnetic field range of 0.1-570 mT and exhibited a minimum detectable magnetic field of 0.1 mT. At a zero-to-peak driving voltage of 60 V, the sensitivity of the PPS-based magnetic sensor reached 10.5 V T-1, which was 1.36 times the value of the aluminum-based magnetic sensor with the same principle and dimensions.
A Method for Studying the Electric Field Enhanced Emission of Carriers from Deep Levels
NASA Astrophysics Data System (ADS)
Hwang, In Duk; Choe, Byungdoo
1986-11-01
A spectroscopic method is proposed for studying the electric field enhanced emission of trapped carriers from deep levels. The resulting spectrum directly represents the effect of the electric field enhanced emission only, thus removing the intrinsic difficulty in treating the electric field enhanced emission from deep levels of large concentration. This method involves two steps of measurements of the ionized trap densities; in the first step the electric field pulse is applied to induce an enhanced emission, and in the second without the electric field pulse. Experimental results by this method have been given for the DX center in LPE Al068Ga0.32As:Sn.
Two stochastic mean-field polycrystal plasticity methods
Tonks, Michael
2008-01-01
In this work, we develop two mean-field polycrystal plasticity models in which the L{sup c} are approximated stochastically. Through comprehensive CPFEM analyses of an idealized tantalum polycrystal, we verify that the L{sup c} tend to follow a normal distribution and surmise that this is due to the crystal interactions. We draw on these results to develop the STM and the stochastic no-constraints model (SNCM), which differ in the manner in which the crystal strain rates D{sup c} are prescribed. Calibration and validation of the models are performed using data from tantalum compression experiments. Both models predict the compression textures more accurately than the FCM, and the SNCM predicts them more accurately than the STM. The STM is extremely computationally efficient, only slightly more expensive than the FCM, while the SNCM is three times more computationally expensive than the STM.
NASA Astrophysics Data System (ADS)
Lensky, Vadim; Birse, Michael C.; Walet, Niels R.
2016-09-01
We construct a coordinate-space potential based on pionless effective field theory (EFT) with a Gaussian regulator. Charge-symmetry breaking is included through the Coulomb potential and through two- and three-body contact interactions. Starting with the effective field theory potential, we apply the stochastic variational method to determine the ground states of nuclei with mass number A ≤4 . At next-to-next-to-leading order, two out of three independent three-body parameters can be fitted to the three-body binding energies. To fix the remaining one, we look for a simultaneous description of the binding energy of 4He and the charge radii of 3He and 4He. We show that at the order considered we can find an acceptable solution, within the uncertainty of the expansion. We find that the EFT expansion shows good agreement with empirical data within the estimated uncertainty, even for a system as dense as 4He.
Field study of hydrogeologic characterization methods in a heterogeneous aquifer.
Alexander, Matthew; Berg, Steven J; Illman, Walter A
2011-01-01
Hydraulic conductivity (K) and specific storage (S(s)) are required parameters when designing transient groundwater flow models. The purpose of this study was to evaluate the ability of commonly used hydrogeologic characterization approaches to accurately delineate the distribution of hydraulic properties in a highly heterogeneous glaciofluvial deposit. The metric used to compare the various approaches was the prediction of drawdown responses from three separate pumping tests. The study was conducted at a field site, where a 15 m × 15 m area was instrumented with four 18-m deep Continuous Multichannel Tubing (CMT) wells. Each CMT well contained seven 17 cm × 1.9 cm monitoring ports equally spaced every 2 m down each CMT system. An 18-m deep pumping well with eight separate 1-m long screens spaced every 2 m was also placed in the center of the square pattern. In each of these boreholes, cores were collected and characterized using the Unified Soil Classification System, grain size analysis, and permeameter tests. To date, 471 K estimates have been obtained through permeameter analyses and 270 K estimates from empirical relationships. Geostatistical analysis of the small-scale K data yielded strongly heterogeneous K fields in three-dimensions. Additional K estimates were obtained through slug tests in 28 ports of the four CMT wells. Several pumping tests were conducted using the multiscreen and CMT wells to obtain larger scale estimates of both K and S(s). The various K and S(s) estimates were then quantitatively evaluated by simulating transient drawdown data from three pumping tests using a 3D forward numerical model constructed using HydroGeoSphere (Therrien et al. 2005). Results showed that, while drawdown predictions generally improved as more complexity was introduced into the model, the ability to make accurate drawdown predictions at all CMT ports was inconsistent.
Thors, Björn; Thielens, Arno; Fridén, Jonas; Colombi, Davide; Törnevik, Christer; Vermeeren, Günter; Martens, Luc; Joseph, Wout
2014-05-01
In this paper, different methods for practical numerical radio frequency exposure compliance assessments of radio base station products were investigated. Both multi-band base station antennas and antennas designed for multiple input multiple output (MIMO) transmission schemes were considered. For the multi-band case, various standardized assessment methods were evaluated in terms of resulting compliance distance with respect to the reference levels and basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Both single frequency and multiple frequency (cumulative) compliance distances were determined using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 and 2600 MHz. The assessments were conducted in terms of root-mean-squared electromagnetic fields, whole-body averaged specific absorption rate (SAR) and peak 10 g averaged SAR. In general, assessments based on peak field strengths were found to be less computationally intensive, but lead to larger compliance distances than spatial averaging of electromagnetic fields used in combination with localized SAR assessments. For adult exposure, the results indicated that even shorter compliance distances were obtained by using assessments based on localized and whole-body SAR. Numerical simulations, using base station products employing MIMO transmission schemes, were performed as well and were in agreement with reference measurements. The applicability of various field combination methods for correlated exposure was investigated, and best estimate methods were proposed. Our results showed that field combining methods generally considered as conservative could be used to efficiently assess compliance boundary dimensions of single- and dual-polarized multicolumn base station antennas with only minor increases in compliance distances.
FIELD MEASUREMENT OF DISSOLVED OXYGEN: A COMPARISON OF METHODS
The ability to confidently measure the concentration of dissolved oxygen (D.O.) in ground water is a key aspect of remedial selection and assessment. Presented here is a comparison of the commonly practiced methods for determining D.O. concentrations in ground water, including c...
An Implicit Characteristic Based Method for Electromagnetics
NASA Technical Reports Server (NTRS)
Beggs, John H.; Briley, W. Roger
2001-01-01
An implicit characteristic-based approach for numerical solution of Maxwell's time-dependent curl equations in flux conservative form is introduced. This method combines a characteristic based finite difference spatial approximation with an implicit lower-upper approximate factorization (LU/AF) time integration scheme. This approach is advantageous for three-dimensional applications because the characteristic differencing enables a two-factor approximate factorization that retains its unconditional stability in three space dimensions, and it does not require solution of tridiagonal systems. Results are given both for a Fourier analysis of stability, damping and dispersion properties, and for one-dimensional model problems involving propagation and scattering for free space and dielectric materials using both uniform and nonuniform grids. The explicit Finite Difference Time Domain Method (FDTD) algorithm is used as a convenient reference algorithm for comparison. The one-dimensional results indicate that for low frequency problems on a highly resolved uniform or nonuniform grid, this LU/AF algorithm can produce accurate solutions at Courant numbers significantly greater than one, with a corresponding improvement in efficiency for simulating a given period of time. This approach appears promising for development of dispersion optimized LU/AF schemes for three dimensional applications.
Xu, Danfeng; Gu, Bing; Rui, Guanghao; Zhan, Qiwen; Cui, Yiping
2016-02-22
We present an arbitrary vector field with hybrid polarization based on the combination of a pair of orthogonal elliptically polarized base vectors on the Poincaré sphere. It is shown that the created vector field is only dependent on the latitude angle 2χ but is independent on the longitude angle 2ψ on the Poincaré sphere. By adjusting the latitude angle 2χ, which is related to two identical waveplates in a common path interferometric arrangement, one could obtain arbitrary type of vector fields. Experimentally, we demonstrate the generation of such kind of vector fields and confirm the distribution of state of polarization by the measurement of Stokes parameters. Besides, we investigate the tight focusing properties of these vector fields. It is found that the additional degree of freedom 2χ provided by arbitrary vector field with hybrid polarization allows one to control the spatial structure of polarization and to engineer the focusing field. PMID:26907066
A new method of UCN production using a spatially alternating magnetic field with spin flips
NASA Astrophysics Data System (ADS)
Sakai, K.; Asahi, K.; Ogawa, H.; Goto, A.; Yogo, K.; Suga, T.; Miyoshi, H.; Kameda, D.; Utsuro, M.; Okumura, K.; Hino, M.; Yoshimi, A.
2001-06-01
Neutrons with energies E below the Fermi effective potential Ueff~0.2 μeV are called ultracold neutrons (UCN), which are totally reflected from a surface of material and thus can be stored in a bottle. The UCN in a bottle are of a great advantage for high-precision measurements in fundamental physics with neutrons, where the UCN density ρUCN takes the key role. We have proposed a new method for the production of UCN, which is based on the repeated application of a field-gradient force on a magnetic moment realized with a spatially alternating field and the correlated spin flips. To evaluate the feasibility and performance of the method, a computer simulation of neutron decelerating and transporting processes has been performed. The result indicates that the UCN density ρUCN in a storage bottle in the present method reaches quite large values as ρUCN~2.2×103 n/cm3 in a realistic condition. An experiment to test the principle and to explore the technical ingredients of the present method is being conducted using the UCN beam from the supermirror turbine at KUR. .
New method for generating linear transfer matrices through combined rf and solenoid fields
NASA Astrophysics Data System (ADS)
Gulliford, Colwyn; Bazarov, Ivan
2012-02-01
We present a new method for computing the transverse transfer matrix for superimposed axisymmetric rf and solenoid field maps. The algorithm constructs the transfer matrix directly from one-dimensional rf and solenoid field maps without computing numerical derivatives or eigenfunction expansions of the field map data. In addition, this method accurately describes the dynamics of low energy particles starting from a solenoid-immersed cathode, allowing the method to simulate transport through both rf and electrostatic guns. Comparison of particle tracking with the transfer matrix, and direct integration of the equations of motion through several field setups, shows excellent agreement between the two methods.
Field effect type devices based on highly doped conducting polymer
NASA Astrophysics Data System (ADS)
Waldmann, O.; Park, J. H.; Hsu, F. C.; Chiou, N. R.; Kim, Y. R.; Epstein, A. J.
2003-03-01
Field-effect type devices based on the highly doped polymer poly(3,4-ethylenedioxythiophene)/polystyrene sulfonic acid (PEDOT/PSS) show a reversible change of the source-drain current by several orders of magnitude upon application of appropriate gate voltages. However, the underlying physical mechanism of their operation is little understood so far. A field-effect like operation, dopant ion diffusion, or electrochemical process has been conjectured. In this work, we investigated devices fabricated on glass substrates with polyvinyl phenol and aluminum as dielectric layer and gate, respectively. We applied a saw tooth shaped voltage profile to the gate electrode and a very small source-drain voltage while measuring gate and source-drain currents. These measurements resemble capacitance-voltage measurements used to study the field-effect in inorganic devices as well as cyclic voltammetry used in electrochemical work. Conclusions concerning the operation principle will be discussed. Supported in part by ONR.
NASA Astrophysics Data System (ADS)
Mhabary, Ziv; Levi, Ofer; Small, Eran; Stern, Adrian
2016-06-01
Recently we have introduced a new method for refocusing images from captured light fields. The method is based on the fractional Fourier transform and allows refocusing a stack of images with a single step. The new techniques is computational efficient and more exact than alternative ones as it doesn't need any interpolations. Here we overview the method present a comparison of our technique to other refocusing techniques.
Coakley, K J; Imtiaz, A; Wallis, T M; Weber, J C; Berweger, S; Kabos, P
2015-03-01
Near-field scanning microwave microscopy offers great potential to facilitate characterization, development and modeling of materials. By acquiring microwave images at multiple frequencies and amplitudes (along with the other modalities) one can study material and device physics at different lateral and depth scales. Images are typically noisy and contaminated by artifacts that can vary from scan line to scan line and planar-like trends due to sample tilt errors. Here, we level images based on an estimate of a smooth 2-d trend determined with a robust implementation of a local regression method. In this robust approach, features and outliers which are not due to the trend are automatically downweighted. We denoise images with the Adaptive Weights Smoothing method. This method smooths out additive noise while preserving edge-like features in images. We demonstrate the feasibility of our methods on topography images and microwave |S11| images. For one challenging test case, we demonstrate that our method outperforms alternative methods from the scanning probe microscopy data analysis software package Gwyddion. Our methods should be useful for massive image data sets where manual selection of landmarks or image subsets by a user is impractical.