Surface layer temperature inversion in the Arabian Sea during winter
Digital Repository Service at National Institute of Oceanography (India)
Pankajakshan, T.; Ghosh, A.K.
picture of the actual inversion phenomena occurring in this area. Figure 1 illustrates the procedure adopted in finding the inversion stations. If the temperature difference (Del T) obtained from (T U –T L ) is greater than 0.2°C, then the station... is more or less consistent. Figure 3-A shows the frequency distribution of temperature difference of the inversion layer (Del T). Figure 3-B shows the frequency distribution of the thickness of the inversion layers in meters (Di). Del T is distributed over...
Determination of transient fluid temperature using the inverse method
Directory of Open Access Journals (Sweden)
Jaremkiewicz Magdalena
2014-03-01
Full Text Available This paper proposes an inverse method to obtain accurate measurements of the transient temperature of fluid. A method for unit step and linear rise of temperature is presented. For this purpose, the thermometer housing is modelled as a full cylindrical element (with no inner hole, divided into four control volumes. Using the control volume method, the heat balance equations can be written for each of the nodes for each of the control volumes. Thus, for a known temperature in the middle of the cylindrical element, the distribution of temperature in three nodes and heat flux at the outer surface were obtained. For a known value of the heat transfer coefficient the temperature of the fluid can be calculated using the boundary condition. Additionally, results of experimental research are presented. The research was carried out during the start-up of an experimental installation, which comprises: a steam generator unit, an installation for boiler feed water treatment, a tray-type deaerator, a blow down flashvessel for heat recovery, a steam pressure reduction station, a boiler control system and a steam header made of martensitic high alloy P91 steel. Based on temperature measurements made in the steam header using the inverse method, accurate measurements of the transient temperature of the steam were obtained. The results of the calculations are compared with the real temperature of the steam, which can be determined for a known pressure and enthalpy.
Temperature dependence of mobility in silicon (100) inversion layers at low temperatures
International Nuclear Information System (INIS)
Kawaguchi, Y.; Suzuki, T.; Kawaji, S.
1982-01-01
Electron mobility of Si(100) n-inversion layers in MOSFETs having μsub(peak) (4.2 K) = 4000.6500 and 12000 cm 2 /V x s has been measured at temperatures between 1 and 80 K. The carrier concentration dependence of the mobility extrapolated to T = O and the temperature dependent part of the scattering probability are investigated. (orig.)
Kachar, H.; Mobasheri, M. R.; Abkar, A. A.; Rahim Zadegan, M.
2015-12-01
Increase of temperature with height in the troposphere is called temperature inversion. Parameters such as strength and depth are characteristics of temperature inversion. Inversion strength is defined as the temperature difference between the surface and the top of the inversion and the depth of inversion is defined as the height of the inversion from the surface. The common approach in determination of these parameters is the use of Radiosonde where these measurements are too sparse. The main objective of this study is detection and modeling the temperature inversion using MODIS thermal infrared data. There are more than 180 days per year in which the temperature inversion conditions are present in Kermanshah city. Kermanshah weather station was selected as the study area. 90 inversion days was selected from 2007 to 2008 where the sky was clear and the Radiosonde data were available. Brightness temperature for all thermal infrared bands of MODIS was calculated for these days. Brightness temperature difference between any of the thermal infrared bands of MODIS and band 31 was found to be sensitive to strength and depth of temperature inversion. Then correlation coefficients between these pairs and the inversion depth and strength both calculated from Radiosonde were evaluated. The results showed poor linear correlation. This was found to be due to the change of the atmospheric water vapor content and the relatively weak temperature inversion strength and depth occurring in Kermanshah. The polynomial mathematical models and Artificial intelligence algorithms were deployed for detection and modeling the temperature inversion. A model with the lowest terms and highest possible accuracy was obtained. The Model was tested using 20 independent test data. Results indicate that the inversion strength can be estimated with RMSE of 0.84° C and R2 of 0.90. Also inversion depth can be estimated with RMSE of 54.56 m and R2 of 0.86.
International Nuclear Information System (INIS)
Kubo, S; Ioka, S; Onchi, S; Matsumoto, Y
2010-01-01
When slug flow runs through a pipe, nonuniform and time-varying thermal stresses develop and there is a possibility that thermal fatigue occurs. Therefore it is necessary to know the temperature distributions and the stress distributions in the pipe for the integrity assessment of the pipe. It is, however, difficult to measure the inner surface temperature directly. Therefore establishment of the estimation method of the temperature history on inner surface of pipe is needed. As a basic study on the estimation method of the temperature history on the inner surface of a pipe with slug flow, this paper presents an estimation method of the temperature on the inner surface of a plate from the temperature on the outer surface. The relationship between the temperature history on the outer surface and the inner surface is obtained analytically. Using the results of the mathematical analysis, the inverse analysis method of the inner surface temperature history estimation from the outer surface temperature history is proposed. It is found that the inner surface temperature history can be estimated from the outer surface temperature history by applying the inverse analysis method, even when it is expressed by the multiple frequency components.
Kimes, D. S.
1983-01-01
A physically based sensor response model of a row crop was used as the mathematical framework from which several inversion strategies were tested for extracting row structure information and component temperatures using a series of sensor view angles. The technique was evaluated on ground-based radiometric thermal infrared data of a cotton row crop that covered 48 percent of the ground in the vertical projection. The results showed that the accuracies of the predicted row heights and widths, vegetation temperatures, and soil temperatures of the cotton row crop were on the order of 5 cm, 1 deg, and 2 deg C, respectively. The inversion techniques can be applied to directional sensor data from aircraft platforms and even space platforms if the effects of atmospheric absorption and emission can be corrected. In theory, such inversion techniques can be applied to a wide variety of vegetation types and thus can have significant implications for remote sensing research and applications in disciplines that deal with incomplete vegetation canopies.
Surface layer temperature inversion in the Bay of Bengal
Digital Repository Service at National Institute of Oceanography (India)
Pankajakshan, T.; Gopalakrishna, V.V.; Muraleedharan, P.M.; Reddy, G.V.; Araligidad, N.
shows heat gain in this region, the organised inversions in this region appears to be generated by the cold fresher water advection (from the head of the bay and Irrawadi basin) over the remnant of the warm saline water in this region advected...
Wallace, Julie; Nair, Parameswaran; Kanaroglou, Pavlos
2010-08-01
Temperature inversions result in the accumulation of air pollution, often to levels exceeding air quality criteria. The respiratory response may be detectable in sputum cell counts. This study investigates the effect of boundary layer temperature inversions on sputum cell counts. Total and differential cell counts of neutrophils, eosinophils, macrophages and lymphocytes were quantified in sputum samples of patients attending an outpatient clinic. Temperature inversions were identified using data from the Atmospheric Infrared Sounder, an atmospheric sensor on the Aqua spacecraft which was launched in 2002 by the National Aeronautics and Space Administration. On inversion days, a statistically significant increase in the percent of cells that were neutrophils was observed in stable patients. There was also a statistically significant increase in the percent of cells that were macrophages, in exacerbated patients. Multivariate linear regression models were used to assess the relationship between temperature inversions and cell counts, controlling patients' age, smoking status, medications and meteorological variables of temperature and humidity. The analyses indicate that, in the stable and exacerbated groups, percent neutrophils and macrophages increased by 12.6% and 2.5%, respectively, on inversion days. These results suggest that temperature inversions need consideration as an exacerbating factor in bronchitis and obstructive airway disease. The effects of air pollutants, nitrogen dioxide, carbon monoxide, fine particulate matter and ozone, were investigated. We identified no significant associations with any pollutant. However, we found that monthly averages of total cell counts were strongly correlated with monthly nitrogen dioxide concentrations, an association not previously identified in the literature.
Digital Repository Service at National Institute of Oceanography (India)
Pankajakshan, T.; Suresh, I.; Gautham, S.; PrasannaKumar, S.; Lengaigne, M.; Rao, R.R; Neetu, S.; Hegde, A
Surface layer temperature inversion (SLTI), a warm layer sandwiched between surface and subsurface colder waters, has been reported to frequently occur in conjunction with barrier layers in the Bay of Bengal (BoB), with potentially commensurable...
Theoretical study on the inverse modeling of deep body temperature measurement
International Nuclear Information System (INIS)
Huang, Ming; Chen, Wenxi
2012-01-01
We evaluated the theoretical aspects of monitoring the deep body temperature distribution with the inverse modeling method. A two-dimensional model was built based on anatomical structure to simulate the human abdomen. By integrating biophysical and physiological information, the deep body temperature distribution was estimated from cutaneous surface temperature measurements using an inverse quasilinear method. Simulations were conducted with and without the heat effect of blood perfusion in the muscle and skin layers. The results of the simulations showed consistently that the noise characteristics and arrangement of the temperature sensors were the major factors affecting the accuracy of the inverse solution. With temperature sensors of 0.05 °C systematic error and an optimized 16-sensor arrangement, the inverse method could estimate the deep body temperature distribution with an average absolute error of less than 0.20 °C. The results of this theoretical study suggest that it is possible to reconstruct the deep body temperature distribution with the inverse method and that this approach merits further investigation. (paper)
Adolph, Alden C.; Albert, Mary R.; Hall, Dorothy K.
2018-03-01
As rapid warming of the Arctic occurs, it is imperative that climate indicators such as temperature be monitored over large areas to understand and predict the effects of climate changes. Temperatures are traditionally tracked using in situ 2 m air temperatures and can also be assessed using remote sensing techniques. Remote sensing is especially valuable over the Greenland Ice Sheet, where few ground-based air temperature measurements exist. Because of the presence of surface-based temperature inversions in ice-covered areas, differences between 2 m air temperature and the temperature of the actual snow surface (referred to as skin temperature) can be significant and are particularly relevant when considering validation and application of remote sensing temperature data. We present results from a field campaign extending from 8 June to 18 July 2015, near Summit Station in Greenland, to study surface temperature using the following measurements: skin temperature measured by an infrared (IR) sensor, 2 m air temperature measured by a National Oceanic and Atmospheric Administration (NOAA) meteorological station, and a Moderate Resolution Imaging Spectroradiometer (MODIS) surface temperature product. Our data indicate that 2 m air temperature is often significantly higher than snow skin temperature measured in situ, and this finding may account for apparent biases in previous studies of MODIS products that used 2 m air temperature for validation. This inversion is present during our study period when incoming solar radiation and wind speed are both low. As compared to our in situ IR skin temperature measurements, after additional cloud masking, the MOD/MYD11 Collection 6 surface temperature standard product has an RMSE of 1.0 °C and a mean bias of -0.4 °C, spanning a range of temperatures from -35 to -5 °C (RMSE = 1.6 °C and mean bias = -0.7 °C prior to cloud masking). For our study area and time series, MODIS surface temperature products agree with skin surface
Directory of Open Access Journals (Sweden)
Zunjian Bian
2017-07-01
Full Text Available The inversion of land surface component temperatures is an essential source of information for mapping heat fluxes and the angular normalization of thermal infrared (TIR observations. Leaf and soil temperatures can be retrieved using multiple-view-angle TIR observations. In a satellite-scale pixel, the clumping effect of vegetation is usually present, but it is not completely considered during the inversion process. Therefore, we introduced a simple inversion procedure that uses gap frequency with a clumping index (GCI for leaf and soil temperatures over both crop and forest canopies. Simulated datasets corresponding to turbid vegetation, regularly planted crops and randomly distributed forest were generated using a radiosity model and were used to test the proposed inversion algorithm. The results indicated that the GCI algorithm performed well for both crop and forest canopies, with root mean squared errors of less than 1.0 °C against simulated values. The proposed inversion algorithm was also validated using measured datasets over orchard, maize and wheat canopies. Similar results were achieved, demonstrating that using the clumping index can improve inversion results. In all evaluations, we recommend using the GCI algorithm as a foundation for future satellite-based applications due to its straightforward form and robust performance for both crop and forest canopies using the vegetation clumping index.
Inverse analysis of non-uniform temperature distributions using multispectral pyrometry
Fu, Tairan; Duan, Minghao; Tian, Jibin; Shi, Congling
2016-05-01
Optical diagnostics can be used to obtain sub-pixel temperature information in remote sensing. A multispectral pyrometry method was developed using multiple spectral radiation intensities to deduce the temperature area distribution in the measurement region. The method transforms a spot multispectral pyrometer with a fixed field of view into a pyrometer with enhanced spatial resolution that can give sub-pixel temperature information from a "one pixel" measurement region. A temperature area fraction function was defined to represent the spatial temperature distribution in the measurement region. The method is illustrated by simulations of a multispectral pyrometer with a spectral range of 8.0-13.0 μm measuring a non-isothermal region with a temperature range of 500-800 K in the spot pyrometer field of view. The inverse algorithm for the sub-pixel temperature distribution (temperature area fractions) in the "one pixel" verifies this multispectral pyrometry method. The results show that an improved Levenberg-Marquardt algorithm is effective for this ill-posed inverse problem with relative errors in the temperature area fractions of (-3%, 3%) for most of the temperatures. The analysis provides a valuable reference for the use of spot multispectral pyrometers for sub-pixel temperature distributions in remote sensing measurements.
Wang, S.L.; Son, P.C. van; Wees, B.J. van; Klapwijk, T.M.
1992-01-01
The conductance of ballistic point contacts in high-mobility Si-inversion layers has been studied at several temperatures between 75 and 600 mK both without and in a magnetic field (up to 12T). When the width of constriction is varied in zero magnetic field, step-like features at multiples of 4e2/h
Vitasse, Yann; Klein, Geoffrey; Kirchner, James W.; Rebetez, Martine
2017-11-01
Some of the world's valleys are famous for having particularly cold microclimates. The La Brevine valley, in the Swiss Jura Mountains, holds the record for the lowest temperature ever measured in an inhabited location in Switzerland. We studied cold air pools (CAPs) in this valley during the winter of 2014-2015 using 44 temperature data loggers distributed between 1033 and 1293 m asl. Our goals were to (i) describe the climatic conditions under which CAPs form in the valley, (ii) examine the spatial configuration and the temperature structure of the CAPs and (iii) quantify how often temperature inversions occur in winter using long-term series of temperature from the valley floor. Our results show that CAPs occurred every second night, on average, during the winter of 2014-2015 and were typically formed under cloudless, windless and high-pressure conditions. Strong temperature inversions up to 28 °C were detected between the valley floor and the surrounding hills. The spatial temperature structure of the CAPs varies among the different inversion days, with the upper boundary of the cold pool generally situated at about 1150 m asl. Although mean temperatures have increased in this area over the period 1960-2015 in connection with climate change, the occurrences of extreme cold temperatures did not decrease in winter and are highly correlated with the North Atlantic Oscillation and the East Atlantic indices. This suggests that CAPs in sheltered valleys are largely decoupled from the free atmosphere temperature and will likely continue to occur in the next decades under warmer conditions.
Directory of Open Access Journals (Sweden)
Marcelo Ribeiro dos Santos
2014-01-01
Full Text Available During machining energy is transformed into heat due to plastic deformation of the workpiece surface and friction between tool and workpiece. High temperatures are generated in the region of the cutting edge, which have a very important influence on wear rate of the cutting tool and on tool life. This work proposes the estimation of heat flux at the chip-tool interface using inverse techniques. Factors which influence the temperature distribution at the AISI M32C high speed steel tool rake face during machining of a ABNT 12L14 steel workpiece were also investigated. The temperature distribution was predicted using finite volume elements. A transient 3D numerical code using irregular and nonstaggered mesh was developed to solve the nonlinear heat diffusion equation. To validate the software, experimental tests were made. The inverse problem was solved using the function specification method. Heat fluxes at the tool-workpiece interface were estimated using inverse problems techniques and experimental temperatures. Tests were performed to study the effect of cutting parameters on cutting edge temperature. The results were compared with those of the tool-work thermocouple technique and a fair agreement was obtained.
Directory of Open Access Journals (Sweden)
A. C. Adolph
2018-03-01
Full Text Available As rapid warming of the Arctic occurs, it is imperative that climate indicators such as temperature be monitored over large areas to understand and predict the effects of climate changes. Temperatures are traditionally tracked using in situ 2 m air temperatures and can also be assessed using remote sensing techniques. Remote sensing is especially valuable over the Greenland Ice Sheet, where few ground-based air temperature measurements exist. Because of the presence of surface-based temperature inversions in ice-covered areas, differences between 2 m air temperature and the temperature of the actual snow surface (referred to as skin temperature can be significant and are particularly relevant when considering validation and application of remote sensing temperature data. We present results from a field campaign extending from 8 June to 18 July 2015, near Summit Station in Greenland, to study surface temperature using the following measurements: skin temperature measured by an infrared (IR sensor, 2 m air temperature measured by a National Oceanic and Atmospheric Administration (NOAA meteorological station, and a Moderate Resolution Imaging Spectroradiometer (MODIS surface temperature product. Our data indicate that 2 m air temperature is often significantly higher than snow skin temperature measured in situ, and this finding may account for apparent biases in previous studies of MODIS products that used 2 m air temperature for validation. This inversion is present during our study period when incoming solar radiation and wind speed are both low. As compared to our in situ IR skin temperature measurements, after additional cloud masking, the MOD/MYD11 Collection 6 surface temperature standard product has an RMSE of 1.0 °C and a mean bias of −0.4 °C, spanning a range of temperatures from −35 to −5 °C (RMSE = 1.6 °C and mean bias = −0.7 °C prior to cloud masking. For our study area and time series
DEFF Research Database (Denmark)
Ren, Tao; Modest, Michael F.; Fateev, Alexander
2015-01-01
In this study, we present an inverse calculation model based on the Levenberg-Marquardt optimization method to reconstruct temperature and species concentration from measured line-of-sight spectral transmissivity data for homogeneous gaseous media. The high temperature gas property database HITEMP...... 2010 (Rothman et al. (2010) [1]), which contains line-by-line (LBL) information for several combustion gas species, such as CO2 and H2O, was used to predict gas spectral transmissivities. The model was validated by retrieving temperatures and species concentrations from experimental CO2 and H2O...
Saidaminov, Makhsud I.
2015-07-06
Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3+, X=Br− or I−) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at elevated temperatures. The crystals can be both size- and shape-controlled by manipulating the different crystallization parameters. Despite the rapidity of the method, the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPbX3 reported to date. The phenomenon of inverse or retrograde solubility and its correlated inverse temperature crystallization strategy present a major step forward for advancing the field on perovskite crystallization.
Roemer, R B; Booth, D; Bhavsar, A A; Walter, G H; Terry, L I
2012-12-21
A mathematical model based on conservation of energy has been developed and used to simulate the temperature responses of cones of the Australian cycads Macrozamia lucida and Macrozamia. macleayi during their daily thermogenic cycle. These cones generate diel midday thermogenic temperature increases as large as 12 °C above ambient during their approximately two week pollination period. The cone temperature response model is shown to accurately predict the cones' temperatures over multiple days as based on simulations of experimental results from 28 thermogenic events from 3 different cones, each simulated for either 9 or 10 sequential days. The verified model is then used as the foundation of a new, parameter estimation based technique (termed inverse calorimetry) that estimates the cones' daily metabolic heating rates from temperature measurements alone. The inverse calorimetry technique's predictions of the major features of the cones' thermogenic metabolism compare favorably with the estimates from conventional respirometry (indirect calorimetry). Because the new technique uses only temperature measurements, and does not require measurements of oxygen consumption, it provides a simple, inexpensive and portable complement to conventional respirometry for estimating metabolic heating rates. It thus provides an additional tool to facilitate field and laboratory investigations of the bio-physics of thermogenic plants. Copyright © 2012 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Mernild, Sebastian Haugard [Los Alamos National Laboratory; Liston, Glen [COLORADO STATE UNIV.
2009-01-01
In many applications, a realistic description of air temperature inversions is essential for accurate snow and glacier ice melt, and glacier mass-balance simulations. A physically based snow-evolution modeling system (SnowModel) was used to simulate eight years (1998/99 to 2005/06) of snow accumulation and snow and glacier ice ablation from numerous small coastal marginal glaciers on the SW-part of Ammassalik Island in SE Greenland. These glaciers are regularly influenced by inversions and sea breezes associated with the adjacent relatively low temperature and frequently ice-choked fjords and ocean. To account for the influence of these inversions on the spatiotemporal variation of air temperature and snow and glacier melt rates, temperature inversion routines were added to MircoMet, the meteorological distribution sub-model used in SnowModel. The inversions were observed and modeled to occur during 84% of the simulation period. Modeled inversions were defined not to occur during days with strong winds and high precipitation rates due to the potential of inversion break-up. Field observations showed inversions to extend from sea level to approximately 300 m a.s.l., and this inversion level was prescribed in the model simulations. Simulations with and without the inversion routines were compared. The inversion model produced air temperature distributions with warmer lower elevation areas and cooler higher elevation areas than without inversion routines due to the use of cold sea-breeze base temperature data from underneath the inversion. This yielded an up to 2 weeks earlier snowmelt in the lower areas and up to 1 to 3 weeks later snowmelt in the higher elevation areas of the simulation domain. Averaged mean annual modeled surface mass-balance for all glaciers (mainly located above the inversion layer) was -720 {+-} 620 mm w.eq. y{sup -1} for inversion simulations, and -880 {+-} 620 mm w.eq. y{sup -1} without the inversion routines, a difference of 160 mm w.eq. y
International Nuclear Information System (INIS)
Kuroyanagi, Toshiyuki
1983-07-01
Based on an idea that surface conditions should be a reflection of interior temperature and interior heat flux variation as inverse as interior conditions has been determined completely by the surface temperature and/on surface heat flux as boundary conditions, a method is presented for determining the surface temperature and the surface heat flux of a solid when the temperature and heat flux at an interior point are a prescribed function of time. The method is developed by the integration of Duhumels' integral which has unknown temperature or unknown heat flux in its integrand. Specific forms of surface condition determination are developed for a sample inverse problem: slab. Ducussing the effect of a degree of avairable informations at an interior point due to damped system and the effect of variation of surface conditions on those formulations, it is shown that those formulations are capable of representing the unknown surface conditions except for small time interval followed by discontinuous change of surface conditions. The small un-resolved time interval is demonstrated by a numerical example. An evaluation method of heat flux at an interior point, which is requested by those formulations, is discussed. (author)
Czech Academy of Sciences Publication Activity Database
Majorowicz, J. A.; Šafanda, Jan
2001-01-01
Roč. 29, 3/4 (2001), s. 231-239 ISSN 0921-8181 Grant - others:UNESCO(XX) IGCP No.428 Institutional research plan: CEZ:AV0Z3012916 Keywords : global warming * geothermics * borehole temperatures * ground temperatures Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.381, year: 2001
Guo, Zhouchao; Lu, Tao; Liu, Bo
2017-04-01
Turbulent penetration can occur when hot and cold fluids mix in a horizontal T-junction pipe at nuclear plants. Caused by the unstable turbulent penetration, temperature fluctuations with large amplitude and high frequency can lead to time-varying wall thermal stress and even thermal fatigue on the inner wall. Numerous cases, however, exist where inner wall temperatures cannot be measured and only outer wall temperature measurements are feasible. Therefore, it is one of the popular research areas in nuclear science and engineering to estimate temperature fluctuations on the inner wall from measurements of outer wall temperatures without damaging the structure of the pipe. In this study, both the one-dimensional (1D) and the two-dimensional (2D) inverse heat conduction problem (IHCP) were solved to estimate the temperature fluctuations on the inner wall. First, numerical models of both the 1D and the 2D direct heat conduction problem (DHCP) were structured in MATLAB, based on the finite difference method with an implicit scheme. Second, both the 1D IHCP and the 2D IHCP were solved by the steepest descent method (SDM), and the DHCP results of temperatures on the outer wall were used to estimate the temperature fluctuations on the inner wall. Third, we compared the temperature fluctuations on the inner wall estimated by the 1D IHCP with those estimated by the 2D IHCP in four cases: (1) when the maximum disturbance of temperature of fluid inside the pipe was 3°C, (2) when the maximum disturbance of temperature of fluid inside the pipe was 30°C, (3) when the maximum disturbance of temperature of fluid inside the pipe was 160°C, and (4) when the fluid temperatures inside the pipe were random from 50°C to 210°C.
A method to estimate the height of temperature inversion layer and the effective mixing depht
International Nuclear Information System (INIS)
Nicolli, D.
1978-05-01
A review of the concept PBL or turbulent boundary layer is made as it is understood in meteorology. Some features of the PBL parameterization are also discussed, as well as the methods used to estimate the temperature inversion heights during morning and afternoon hours. The study bases on the assumption of the dry adiabatic lapse rate in the mixing layer that is, water vapor and airborne material are supposed to be homogeneously mixed below the inversion layer or in the effective mixing depth. The mean mixing heights over Rio de Janeiro area respectively about 500m and 1000m at morning and afternoon hours. For Sao Paulo these values are respectively 400m and 1300m at morning and afternoon hours [pt
Prediction inverse d'un front de solidification dans un four de transformation a haute temperature
Marois, Marc-Andre
Ce projet de recherche porte sur une methode numerique permettant de predire l'evolution du profil 2D de la couche solide qui recouvre l'interieur des parois de plusieurs fours de transformation a haute temperature. Un modele mathematique base sur la formulation faible de l'energie est d'abord developpe et valide. Une methode de transfert thermique inverse reposant sur ce modele est ensuite developpee afin d'obtenir une mesure rapide et continue de l'evolution du profil de cette couche solide. Vu la grande inertie thermique du systeme a l'etude, differentes strategies sont proposees afin de faciliter la mise en uvre de cette methode numerique. Finalement, cette approche inverse est confrontee aux resultats experimentaux obtenus a l'aide d'un reacteur metallurgique. Une etude preliminaire montre que les fours de transformation presentent une tres grande inertie thermique qui limite grandement l'utilisation des methodes inverses. En effet, la sensibilite de cette methode numerique repose essentiellement sur le delai temporel observe entre la variation du profil du banc et la fluctuation de la temperature a la surface externe de la paroi du four. Les resultats obtenus demontrent qu'une partie de ce delai est proportionnel a la chaleur latente de fusion lorsque le materiau a changement de phase est constitue d'un melange non eutectique. Afin de limiter l'impact de ce delai temporel, deux astuces numeriques sont proposees : reutiliser plus d'une fois les mesures de temperature et modifier le probleme thermique dans les regions pateuse et liquide. D'une part, le concept de chevauchement propose permet de reduire le temps d'acquisition des donnees entre chacune des predictions. D'autre part, l'approche virtuelle developpee permet de reduire l'inertie thermique du systeme et, par le fait meme, le delai temporel associe a la diffusion de la chaleur. Ces deux strategies ont permis de predire efficacement l'evolution 1D de l'epaisseur de la couche de gelee qui se solidifie a
Estimation of oil reservoir thermal properties through temperature log data using inversion method
International Nuclear Information System (INIS)
Cheng, Wen-Long; Nian, Yong-Le; Li, Tong-Tong; Wang, Chang-Long
2013-01-01
Oil reservoir thermal properties not only play an important role in steam injection well heat transfer, but also are the basic parameters for evaluating the oil saturation in reservoir. In this study, for estimating reservoir thermal properties, a novel heat and mass transfer model of steam injection well was established at first, this model made full analysis on the wellbore-reservoir heat and mass transfer as well as the wellbore-formation, and the simulated results by the model were quite consistent with the log data. Then this study presented an effective inversion method for estimating the reservoir thermal properties through temperature log data. This method is based on the heat transfer model in steam injection wells, and can be used to predict the thermal properties as a stochastic approximation method. The inversion method was applied to estimate the reservoir thermal properties of two steam injection wells, it was found that the relative error of thermal conductivity for the two wells were 2.9% and 6.5%, and the relative error of volumetric specific heat capacity were 6.7% and 7.0%,which demonstrated the feasibility of the proposed method for estimating the reservoir thermal properties. - Highlights: • An effective inversion method for predicting the oil reservoir thermal properties was presented. • A novel model for steam injection well made full study on the wellbore-reservoir heat and mass transfer. • The wellbore temperature field and steam parameters can be simulated by the model efficiently. • Both reservoirs and formation thermal properties could be estimated simultaneously by the proposed method. • The estimated steam temperature was quite consistent with the field data
Digital Repository Service at National Institute of Oceanography (India)
Murty, T.V.R.; Rao, M.M.M.; Sadhuram, Y.
corresponding to the predicted ray arrivals were identified and travel time perturbations of the most stable Eigen rays enabled reconstruction of temperature anomaly from the sound velocity perturbations using stochastic inverse method. For formulation...
Energy Technology Data Exchange (ETDEWEB)
Mukhopadhyay, S.; Tsang, Y.; Finsterle, S.
2009-01-15
A simple conceptual model has been recently developed for analyzing pressure and temperature data from flowing fluid temperature logging (FFTL) in unsaturated fractured rock. Using this conceptual model, we developed an analytical solution for FFTL pressure response, and a semianalytical solution for FFTL temperature response. We also proposed a method for estimating fracture permeability from FFTL temperature data. The conceptual model was based on some simplifying assumptions, particularly that a single-phase airflow model was used. In this paper, we develop a more comprehensive numerical model of multiphase flow and heat transfer associated with FFTL. Using this numerical model, we perform a number of forward simulations to determine the parameters that have the strongest influence on the pressure and temperature response from FFTL. We then use the iTOUGH2 optimization code to estimate these most sensitive parameters through inverse modeling and to quantify the uncertainties associated with these estimated parameters. We conclude that FFTL can be utilized to determine permeability, porosity, and thermal conductivity of the fracture rock. Two other parameters, which are not properties of the fractured rock, have strong influence on FFTL response. These are pressure and temperature in the borehole that were at equilibrium with the fractured rock formation at the beginning of FFTL. We illustrate how these parameters can also be estimated from FFTL data.
International Nuclear Information System (INIS)
Liu, Sha; Liu, Shi; Tong, Guowei
2017-01-01
In industrial areas, temperature distribution information provides a powerful data support for improving system efficiency, reducing pollutant emission, ensuring safety operation, etc. As a noninvasive measurement technology, acoustic tomography (AT) has been widely used to measure temperature distribution where the efficiency of the reconstruction algorithm is crucial for the reliability of the measurement results. Different from traditional reconstruction techniques, in this paper a two-phase reconstruction method is proposed to ameliorate the reconstruction accuracy (RA). In the first phase, the measurement domain is discretized by a coarse square grid to reduce the number of unknown variables to mitigate the ill-posed nature of the AT inverse problem. By taking into consideration the inaccuracy of the measured time-of-flight data, a new cost function is constructed to improve the robustness of the estimation, and a grey wolf optimizer is used to solve the proposed cost function to obtain the temperature distribution on the coarse grid. In the second phase, the Adaboost.RT based BP neural network algorithm is developed for predicting the temperature distribution on the refined grid in accordance with the temperature distribution data estimated in the first phase. Numerical simulations and experiment measurement results validate the superiority of the proposed reconstruction algorithm in improving the robustness and RA. (paper)
Liu, Sha; Liu, Shi; Tong, Guowei
2017-11-01
In industrial areas, temperature distribution information provides a powerful data support for improving system efficiency, reducing pollutant emission, ensuring safety operation, etc. As a noninvasive measurement technology, acoustic tomography (AT) has been widely used to measure temperature distribution where the efficiency of the reconstruction algorithm is crucial for the reliability of the measurement results. Different from traditional reconstruction techniques, in this paper a two-phase reconstruction method is proposed to ameliorate the reconstruction accuracy (RA). In the first phase, the measurement domain is discretized by a coarse square grid to reduce the number of unknown variables to mitigate the ill-posed nature of the AT inverse problem. By taking into consideration the inaccuracy of the measured time-of-flight data, a new cost function is constructed to improve the robustness of the estimation, and a grey wolf optimizer is used to solve the proposed cost function to obtain the temperature distribution on the coarse grid. In the second phase, the Adaboost.RT based BP neural network algorithm is developed for predicting the temperature distribution on the refined grid in accordance with the temperature distribution data estimated in the first phase. Numerical simulations and experiment measurement results validate the superiority of the proposed reconstruction algorithm in improving the robustness and RA.
SPECTROSCOPIC EVIDENCE FOR A TEMPERATURE INVERSION IN THE DAYSIDE ATMOSPHERE OF HOT JUPITER WASP-33b
Energy Technology Data Exchange (ETDEWEB)
Haynes, Korey; Mandell, Avi M. [Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Madhusudhan, Nikku [Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA (United Kingdom); Deming, Drake [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Knutson, Heather, E-mail: khaynes0112@gmail.com [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)
2015-06-20
We present observations of two occultations of the extrasolar planet WASP-33b using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope, which allow us to constrain the temperature structure and composition of its dayside atmosphere. WASP-33b is the most highly irradiated hot Jupiter discovered to date, and the only exoplanet known to orbit a δ-Scuti star. We observed in spatial scan mode to decrease instrument systematic effects in the data, and removed fluctuations in the data due to stellar pulsations. The rms for our final, binned spectrum is 1.05 times the photon noise. We compare our final spectrum, along with previously published photometric data, to atmospheric models of WASP-33b spanning a wide range in temperature profiles and chemical compositions. We find that the data require models with an oxygen-rich chemical composition and a temperature profile that increases at high altitude. We find that our measured spectrum displays an excess in the measured flux toward short wavelengths that is best explained as emission from TiO. If confirmed by additional measurements at shorter wavelengths, this planet would become the first hot Jupiter with a thermal inversion that can be definitively attributed to the presence of TiO in its dayside atmosphere.
Pizzo, Michelle; Daryabeigi, Kamran; Glass, David
2015-01-01
The ability to solve the heat conduction equation is needed when designing materials to be used on vehicles exposed to extremely high temperatures; e.g. vehicles used for atmospheric entry or hypersonic flight. When using test and flight data, computational methods such as finite difference schemes may be used to solve for both the direct heat conduction problem, i.e., solving between internal temperature measurements, and the inverse heat conduction problem, i.e., using the direct solution to march forward in space to the surface of the material to estimate both surface temperature and heat flux. The completed research first discusses the methods used in developing a computational code to solve both the direct and inverse heat transfer problems using one dimensional, centered, implicit finite volume schemes and one dimensional, centered, explicit space marching techniques. The developed code assumed the boundary conditions to be specified time varying temperatures and also considered temperature dependent thermal properties. The completed research then discusses the results of analyzing temperature data measured while radiantly heating a carbon/carbon specimen up to 1920 F. The temperature was measured using thermocouple (TC) plugs (small carbon/carbon material specimens) with four embedded TC plugs inserted into the larger carbon/carbon specimen. The purpose of analyzing the test data was to estimate the surface heat flux and temperature values from the internal temperature measurements using direct and inverse heat transfer methods, thus aiding in the thermal and structural design and analysis of high temperature vehicles.
Directory of Open Access Journals (Sweden)
D. Kaviani
2016-01-01
Full Text Available Objective(s: Nanoemulsions are a kind of emulsions that can be transparent, translucent (size range 50-200 nm or “milky” (up to 500 nm. Nanoemulsions are adequatly effective for transfer of active component through skin which facilitate the entrance of the active component . The transparent nature of the system and lack of the thickener and fluidity are among advantages of nanoemulsion. Materials and Methods: In this study, a nanoemulsion of lemon oil in water was prepared by the phase inversion temperature (PIT emulsification method in which the tween 40 was used as surfactant. The effect of concentration of NaCl in aqueous phase, pH and weight percent of surfactant and aqueous on the PIT and droplet size were investigated. Results: The results showed that with increasing of concentration of NaCl from 0.05 M to 1 M, PIT decrease from 72 to 50. The average droplet sizes, for 0.1, 0.5 and 1 M of NaCl in 25 ºC are 497.3, 308.1 and 189.9 nm, respectively and the polydispersity indexes are 0.348, 0.334 and 0.307, respectively. Conclusion: Considering the characteristics of nanoemulsions such as being transparent, endurance of solution and droplet size can provide suitable reaction environment for polymerization process used in making hygienic and medical materials.
Inversion of Land Surface Temperature (LST Using Terra ASTER Data: A Comparison of Three Algorithms
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Milton Isaya Ndossi
2016-12-01
Full Text Available Land Surface Temperature (LST is an important measurement in studies related to the Earth surface’s processes. The Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER instrument onboard the Terra spacecraft is the currently available Thermal Infrared (TIR imaging sensor with the highest spatial resolution. This study involves the comparison of LSTs inverted from the sensor using the Split Window Algorithm (SWA, the Single Channel Algorithm (SCA and the Planck function. This study has used the National Oceanic and Atmospheric Administration’s (NOAA data to model and compare the results from the three algorithms. The data from the sensor have been processed by the Python programming language in a free and open source software package (QGIS to enable users to make use of the algorithms. The study revealed that the three algorithms are suitable for LST inversion, whereby the Planck function showed the highest level of accuracy, the SWA had moderate level of accuracy and the SCA had the least accuracy. The algorithms produced results with Root Mean Square Errors (RMSE of 2.29 K, 3.77 K and 2.88 K for the Planck function, the SCA and SWA respectively.
Qiu, Shaoyue; Dong, Xiquan; Xi, Baike; Li, J.-L. F.
2015-08-01
In this study, the characteristics of the Arctic mixed-phase cloud (AMC) have been investigated using data collected at the Atmospheric Radiation Measurement North Slope Alaska site from October 2006 to September 2009. AMC has an annual occurrence frequency of 42.3%, which includes 18.7% of single-layered AMCs and 23.6% for multiple layers. Two cloud base heights (CBHs) are defined from ceilometer and micropulse lidar (MPL) measurements. For single-layered AMC, the ceilometer-derived CBH represents the base of the liquid-dominant layer near the cloud top, while MPL-derived CBH represents base of the lower ice-dominant layer. The annual mean CBHs from ceilometer and MPL measurements are 1.0 km and 0.6 km, respectively, with the largest difference ( 1.0 km) occurring from December to March and the smallest difference in September. The humidity inversion occurrence decreases with increasing humidity inversion intensity (stronger in summer than in winter). During the winter months, AMC occurrences increase from 15% to 35% when the inversion intensity increases from 0.1 to 0.9 g/kg. On the contrary, despite a higher frequency of strong humidity inversion in summer, AMC occurrences are nearly invariant for different inversion intensities. On average, humidity and temperature inversion frequencies of occurrence above an AMC are 5 and 8 times, respectively, as high as those below an AMC. The strong inversion occurrences for both humidity and temperature above an AMC provide the moisture sources from above for the formation and maintenance of AMCs. This result helps to reconcile the persistency of AMCs even when the Arctic surface is covered by snow and ice.
Tran, A. P.; Dafflon, B.; Hubbard, S. S.; Kowalsky, M. B.; Tokunaga, T. K.; Faybishenko, B.; Long, P.
2014-12-01
Evaluation of spatiotemporal dynamics of heat transport and water flow in terrestrial environments is essential for understanding hydrological and biogeochemical processes. Electrical resistance tomography has been increasingly well used for monitoring subsurface hydrological processes and estimating soil hydraulic properties through coupled hydrogeophysical inversion. However, electrical resistivity depends on a variety of factors such as temperature, which may limit the accuracy of hydrogeophysical inversion. The main objective of this study is to develop a hydrogeophysical inversion framework to enable the incorporation of nonisothermal processes into the hydrogeophysical inversion procedure, and use of this procedure to investigate the effect of hydrological controls on biogeochemical cycles in terrestrial environments. We developed the coupled hydro-thermal-geophysical inversion approach, using the iTOUGH2 framework. In this framework, the heat transport and water flow are simultaneously modeled with TOUGH2 code, which effectively accounts for the multiphase, multi-component and nonisothermal flow in porous media. A flexible approach is used to incorporate petrophysical relationships and uncertainty to link soil moisture and temperature with the electrical resistivity. The developed approach was applied to both synthetic and field case studies. At the DOE subsurface biogeochemistry field site located near Rifle CO, seasonal snowmelt delivers a hydrological pulse to the system, which in turn influences the cycles of nitrogen, carbon and other critical elements. Using the new approach, we carried out numerical inversion of electrical resistance data collected along a 100 m transect at the Rifle site, and compared the results with field investigations of the soil, vadose zone, including the capillary fringe, and groundwater, as well as temperature and tensiometer measurements. Preliminary results show the importance of accounting for nonisothermal conditions to
Directory of Open Access Journals (Sweden)
Lei Zhang
2015-01-01
Full Text Available In the concrete dam construction, it is very necessary to strengthen the real-time monitoring and scientific management of concrete temperature control. This paper constructs the analysis and inverse analysis system of temperature stress simulation, which is based on various useful data collected in real time in the process of concrete construction. The system can produce automatically data file of temperature and stress calculation and then achieve the remote real-time simulation calculation of temperature stress by using high performance computing techniques, so the inverse analysis can be carried out based on a basis of monitoring data in the database; it fulfills the automatic feedback calculation according to the error requirement and generates the corresponding curve and chart after the automatic processing and analysis of corresponding results. The system realizes the automation and intellectualization of complex data analysis and preparation work in simulation process and complex data adjustment in the inverse analysis process, which can facilitate the real-time tracking simulation and feedback analysis of concrete temperature stress in construction process and enable you to discover problems timely, take measures timely, and adjust construction scheme and can well instruct you how to ensure project quality.
Directory of Open Access Journals (Sweden)
K. Ogo
2016-06-01
Full Text Available Sodium potassium niobate (NKN piezoceramics have been paid much attention as lead-free piezoelectric materials in high temperature devices because of their high Curie temperature. The temperature dependency of their material parameters, however, has not been determined in detail up to now. For this purpose, we exploit the so-called Inverse Method denoting a simulation-based characterization approach. Compared with other characterization methods, the Inverse Method requires only one sample shape of the piezoceramic material and has further decisive advantages. The identification of material parameters showed that NKN is mechanically softer in shear direction compared with lead zirconate titanate (PZT at room temperature. The temperature dependency of the material parameters of NKN was evaluated in the temperature range from 30 °C to 150 °C. As a result, we figured out that dielectric constants and piezoelectric constants show a monotonous and isotropic increment with increasing temperature. On the other hand, elastic stiffness constant c 44 E of NKN significantly decreased in contrast to other elastic stiffness constants. It could be revealed that the decrement of c 44 E is associated with an orthorhombic-tetragonal phase transition. Furthermore, ratio of elastic compliance constants s 44 E / s 33 E exhibited similar temperature dependent behavior to the ratio of piezoelectric constants d15/d33. It is suspected that mechanical softness in shear direction is one origin of the large piezoelectric shear mode of NKN. Our results show that NKN are suitable for high temperature devices, and that the Inverse Method should be a helpful approach to characterize material parameters under their practical operating conditions for NKN.
Inverse iron isotope effect on the transition temperature of the (Ba,K)Fe2As2 superconductor.
Shirage, Parasharam M; Kihou, Kunihiro; Miyazawa, Kiichi; Lee, Chul-Ho; Kito, Hijiri; Eisaki, Hiroshi; Yanagisawa, Takashi; Tanaka, Yasumoto; Iyo, Akira
2009-12-18
We report that the (Ba,K)Fe(2)As(2) superconductor (transition temperature, T(c) approximately 38 K) has an inverse iron isotope coefficient alpha(Fe) = -0.18(3) (where T(c) approximately M(-alphaFe) and M is the iron isotope mass); i.e., the sample containing the large iron isotope mass depicts a higher T(c). Systematic inverse shifts in T(c) were clearly observed between the samples using three types of Fe isotopes ((54)Fe, natural Fe, and (57)Fe). This indicates the first evidence of the inverse isotope effect in high-T(c) superconductors. This anomalous mass dependence on T(c) implies an exotic coupling mechanism in Fe-based superconductors.
Boukabara, S. A.; Garrett, K.
2014-12-01
A one-dimensional variational retrieval system has been developed, capable of producing temperature and water vapor profiles in clear, cloudy and precipitating conditions. The algorithm, known as the Microwave Integrated Retrieval System (MiRS), is currently running operationally at the National Oceanic and Atmospheric Administration (NOAA) National Environmental Satellite Data and Information Service (NESDIS), and is applied to a variety of data from the AMSU-A/MHS sensors on board the NOAA-18, NOAA-19, and MetOp-A/B polar satellite platforms, as well as SSMI/S on board both DMSP F-16 and F18, and from the NPP ATMS sensor. MiRS inverts microwave brightness temperatures into atmospheric temperature and water vapor profiles, along with hydrometeors and surface parameters, simultaneously. This atmosphere/surface coupled inversion allows for more accurate retrievals in the lower tropospheric layers by accounting for the surface emissivity impact on the measurements. It also allows the inversion of the soundings in all-weather conditions thanks to the incorporation of the hydrometeors parameters in the inverted state vector as well as to the inclusion of the emissivity in the same state vector, which is accounted for dynamically for the highly variable surface conditions found under precipitating atmospheres. The inversion is constrained in precipitating conditions by the inclusion of covariances for hydrometeors, to take advantage of the natural correlations that exist between temperature and water vapor with liquid and ice cloud along with rain water. In this study, we present a full assessment of temperature and water vapor retrieval performances in all-weather conditions and over all surface types (ocean, sea-ice, land, and snow) using matchups with radiosonde as well as Numerical Weather Prediction and other satellite retrieval algorithms as references. An emphasis is placed on retrievals in cloudy and precipitating atmospheres, including extreme weather events
International Nuclear Information System (INIS)
Schreier, Michael; Lotze, Johannes; Gross, Rudolf; Goennenwein, Sebastian T B; Bauer, Gerrit E W; Uchida, Ken-ichi; Daimon, Shunsuke; Kikkawa, Takashi; Saitoh, Eiji; Vasyuchka, Vitaliy I; Lauer, Viktor; Chumak, Andrii V; Serga, Alexander A; Hillebrands, Burkard; Flipse, Joost; Van Wees, Bart J
2015-01-01
We carried out a concerted effort to determine the absolute sign of the inverse spin Hall effect voltage generated by spin currents injected into a normal metal. We focus on yttrium iron garnet (YIG)∣platinum bilayers at room temperature, generating spin currents by microwaves and temperature gradients. We find consistent results for different samples and measurement setups that agree with theory. We suggest a right-hand-rule to define a positive spin Hall angle corresponding to the voltage expected for the simple case of scattering of free electrons from repulsive Coulomb charges. (paper)
Osibanjo, Olabosipo O.
The objectives of this work are to calculate surface fluxes for rolling terrain using observational data collected during one week in September 2014 from a monitoring site in Echo, Oregon and to investigate the log law in the ABL. The site is located in the Columbia Basin with rolling terrain, irrigated farmland, and over 100 wind turbines. The 10 m tower was placed in a small valley depression to isolate nighttime temperature inversions. This thesis presents observations of momentum, sensible heat, moisture, and CO2 fluxes from data collected at a sampling frequency of 10Hz at four heights. Results show a strong correlation between temperature inversions and CO 2 flux. The log layer could not be achieved as the value of the estimated von Karman constant (˜0.62) is not close to that of the accepted value of 0.41. The impact of the irrigated farmland near the measurement site was observed in the latent heat flux, where the advection of moisture was evident in the tower moisture gradient. A strong relationship was also observed between fluxes of sensible heat, latent heat, CO2, and atmospheric stability. The average nighttime CO2 concentration observed was ˜407 ppm, and daytime ˜388 ppm compared to the 2013 global average CO2 concentration of 395 ppm. The maximum CO2 concentration (˜485 ppm) was observed on the strongest temperature inversion night. There are few uncertainties in the measurements. The manufacturer for the eddy covariance instruments (EC 150) quotes uncertainty of +/- 0.1°C for temperature between -0°C-40°C. Error bars were generated on the estimated surface sensible heat flux using the standard deviation and mean values. Under the most stable atmospheric conditions, uncertainty (assumed to be the variability in the flux estimates) was close to the minimum (˜+/- 5 W m-2). (Abstract shortened by ProQuest.).
Blacic, T. M.; Jun, H.; Shin, C.; Rosado, H.
2016-02-01
2-D temperature images of the ocean with resolution within a few tens of meters in distance and depth can be recovered from conventional marine multichannel seismic (MCS; low frequency acoustic) data via full waveform inversion (FWI), as demonstrated by several research groups in recent years. A primary limitation with FWI is that the more computationally efficient local inversion methods require an accurate estimate of the background sound speed in the material as a starting point to avoid converging to a local, rather than global, solution. In the ocean, expendable instruments are often used to obtain 1-D temperature and sound speed profiles; in typical MCS data collection, however, expendables are deployed just once per day, resulting in only one hydrographic profile every few hundred kilometers. In addition, the band-limited nature of seismic data, which typically lacks reliable frequencies below 5 Hz, makes it inherently challenging to extract the long wavelength sound speed directly from seismic data. Laplace domain inversion (LDI) developed by Changsoo Shin and colleagues requires only a simple starting model to produce smooth background sound speed models without requiring prior information about the medium. It works by transforming input data to the Laplace domain and then examining the zero frequency component of the damped wavefield to extract a smooth sound speed model. Laplace-Fourier domain inversion extends the technique to include additional frequencies below 5 Hz. This ability to use frequencies below those effectively propagated by the seismic source is what enables LDI to produce the smooth background trend from the data. We applied LDI to five synthetic data sets based on simplified models of oceanographic features and recovered smoothed versions of our synthetic models, demonstrating the viability of this method for creating sound speed profiles suitable for use as starting models for other FWI methods that produce more detailed models.
Inverse estimation of the temperature field within a gas-filled duct section by use of acoustic data
International Nuclear Information System (INIS)
Kim, Tae-Kyoon; Ih, Jeong-Guon
2015-01-01
Knowledge of the temperature distribution of an in-duct gaseous medium is essential in the monitoring of combustion status. To obtain the temperature distribution, an inverse relationship based on the Radon transform is formulated by using the measured time retardation data from a set of acoustic sensors and actuators. The entire spatial distribution can be obtained by interpolating the estimated discrete temperature data using either a path-based or spaced-based method. An interpolation method then determines the precision of the final imaging result. The characteristics and performance of two interpolation methods are investigated in a simulation study by reconstructing the temperature distribution of a rectangular cross-section. To calculate the temperature field, the path-based interpolation method adopts a direct expression of temperature variation along the propagation path, whereas the space-based interpolation method uses data obtained at predetermined points deployed inside the field. The average reconstruction accuracy of the space-based interpolation for temperature fields with 1 and 4 local maxima is 22% and 183% better than that of path-based interpolation, respectively. Also, the space-based interpolation method is more robust with regard to measurement noise than the path-based interpolation method. (paper)
Digital Repository Service at National Institute of Oceanography (India)
Shankar, D.; Gopalakrishna, V.V.; Shenoi, S.S.C.; Durand, F.; Shetye, S.R.; Rajan, C.K.; Johnson, Z.; Araligidad, N.; Michael, G.S.
in April, when the Tropical Convergence Zone moves over the SEAS and the warm pool engulfs the region. Ocean dynamics and air- sea fluxes are together responsible for the formation and westward propagation of the inversions. 1. Introduction Prior.... Even in May, when the Tropical Conver- gence Zone moves over the region and it is engulfed by the warm pool, the SSTH retains its identity within the warm pool [Shenoi et al., 1999]. The onset of the summer monsoon over India is often, but not always...
International Nuclear Information System (INIS)
Fivez, J.; Thoen, J.
2004-01-01
In this article, we apply our analytical theory, published earlier in this journal, to obtain information on the earth surface temperature history from some borehole temperature data. Compared to the results of the five different methods applied to the same temperature data, our method seems to be easier, assumption-free, and yields internally consistent results. The results suggest a cooling a few centuries ago, followed by a continuing warming up to these days, in agreement with a little ice age scenario
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Widawski Artur
2015-06-01
Full Text Available Sosnowiec is located in the Katowice Region, which is the most urbanized and industrialized region in Poland. Urban areas of such character favor enhancement of pollution concentration in the atmosphere and the consequent emergence of smog. Local meteorological and circulation conditions significantly influence not only on the air pollution level but also change air temperature considerably in their centers and immediate vicinities. The synoptic situation also plays the major role in dispersal and concentration of air pollutants and changes in temperature profile. One of the most important are the near-ground (100 m inversions of temperature revealed their highest values on clear winter days and sometimes stay still for the whole day and night. Air temperature inversions in Sosnowiec occur mainly during anticyclone stagnation (Ca-anticyclone centre and Ka-anticyclonic ridge and in anticyclones with air advection from the south and southwest (Sa and SWa which cause significantly increase of air pollution values. The detailed evaluation of the influence of circulation types on the appearance of a particular concentration of pollutants carried out in this work has confirmed the predominant influence of individual circulation types on the development of air pollution levels at the Katowice region. This paper presents research case study results of the thermal structure of the near-ground atmospheric layer (100 m and air pollution parameters (PM10, SO2, NO, NO2 changes in selected days of 2005 year according to regional synoptic circulation types. The changes in urban environment must be taken into account in analyses of multiyear trends of air temperature and air conditions on the regional and global scales.
Ranieri, M L; Huck, J R; Sonnen, M; Barbano, D M; Boor, K J
2009-10-01
The grade A Pasteurized Milk Ordinance specifies minimum processing conditions of 72 degrees C for at least 15 s for high temperature, short time (HTST) pasteurized milk products. Currently, many US milk-processing plants exceed these minimum requirements for fluid milk products. To test the effect of pasteurization temperatures on bacterial numbers in HTST pasteurized milk, 2% fat raw milk was heated to 60 degrees C, homogenized, and treated for 25 s at 1 of 4 different temperatures (72.9, 77.2, 79.9, or 85.2 degrees C) and then held at 6 degrees C for 21 d. Aerobic plate counts were monitored in pasteurized milk samples at d 1, 7, 14, and 21 postprocessing. Bacterial numbers in milk processed at 72.9 degrees C were lower than in milk processed at 85.2 degrees C on each sampling day, indicating that HTST fluid milk-processing temperatures significantly affected bacterial numbers in fluid milk. To assess the microbial ecology of the different milk samples during refrigerated storage, a total of 490 psychrotolerant endospore-forming bacteria were identified using DNA sequence-based subtyping methods. Regardless of processing temperature, >85% of the isolates characterized at d 0, 1, and 7 postprocessing were of the genus Bacillus, whereas more than 92% of isolates characterized at d 14 and 21 postprocessing were of the genus Paenibacillus, indicating that the predominant genera present in HTST-processed milk shifted from Bacillus spp. to Paenibacillus spp. during refrigerated storage. In summary, 1) HTST processing temperatures affected bacterial numbers in refrigerated milk, with higher bacterial numbers in milk processed at higher temperatures; 2) no significant association was observed between genus isolated and pasteurization temperature, suggesting that the genera were not differentially affected by the different processing temperatures; and 3) although typically present at low numbers in raw milk, Paenibacillus spp. are capable of growing to numbers that can
Large ground warming in the Canadian Arctic inferred from inversions of temperature logs
Czech Academy of Sciences Publication Activity Database
Majorowicz, J. A.; Skinner, W. R.; Šafanda, Jan
2004-01-01
Roč. 221, č. 1 (2004), s. 15-25 ISSN 0012-821X Institutional research plan: CEZ:AV0Z3012916 Keywords : global warming * borehole temperatures * ground temperatures Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 3.499, year: 2004
Temperature-dependent anisotropic magnetoresistance inversion behaviors in Fe{sub 3}O{sub 4} films
Energy Technology Data Exchange (ETDEWEB)
Yoon, Kap Soo [Novel Functional Materials and Devices Lab, The Research Institute for Natural Science, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Hong, Jin Pyo, E-mail: jphong@hanyang.ac.kr [Novel Functional Materials and Devices Lab, The Research Institute for Natural Science, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Division of Nano-Scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)
2017-02-01
We address the abnormal anisotropic magnetoresistance (AMR) reversal feature of half-metallic polycrystalline Fe{sub 3}O{sub 4} films occurring at a specific temperature. Experimental results revealed a positive to negative MR transition in the Fe{sub 3}O{sub 4} films at 264 K, which reflect the influence of additional domain wall scattering. These features was described by a correlation between domain wall resistance and inversion behavior of AMR with additional domain wall scattering factors. We further describe a possible model based on systematic structural and electrical measurements that employs a temperature-dependent domain wall width and spin diffusion length of the conducting electrons. This model allows for spin-flipping scattering of spin polarized electrons inside a proper domain width.
Directory of Open Access Journals (Sweden)
Huang Can
2014-08-01
Full Text Available In the present paper, a numerical model combining radiation and conduction for porous materials is developed based on the finite volume method. The model can be used to investigate high-temperature thermal insulations which are widely used in metallic thermal protection systems on reusable launch vehicles and high-temperature fuel cells. The effective thermal conductivities (ECTs which are measured experimentally can hardly be used separately to analyze the heat transfer behaviors of conduction and radiation for high-temperature insulation. By fitting the effective thermal conductivities with experimental data, the equivalent radiation transmittance, absorptivity and reflectivity, as well as a linear function to describe the relationship between temperature and conductivity can be estimated by an inverse problems method. The deviation between the calculated and measured effective thermal conductivities is less than 4%. Using the material parameters so obtained for conduction and radiation, the heat transfer process in multilayer thermal insulation (MTI is calculated and the deviation between the calculated and the measured transient temperatures at a certain depth in the multilayer thermal insulation is less than 6.5%.
Tang, Qunshu; Hobbs, Richard; Zheng, Chan; Biescas, Berta; Caiado, Camila
2016-06-01
Marine seismic reflection technique is used to observe the strong ocean dynamic process of nonlinear internal solitary waves (ISWs or solitons) in the near-surface water. Analysis of ISWs is problematical because of their transient nature and limitations of classical physical oceanography methods. This work explores a Markov Chain Monte Carlo (MCMC) approach to recover the temperature and salinity of ISW field using the seismic reflectivity data and in situ hydrographic data. The MCMC approach is designed to directly sample the posterior probability distributions of temperature and salinity which are the solutions of the system under investigation. The principle improvement is the capability of incorporating uncertainties in observations and prior models which then provide quantified uncertainties in the output model parameters. We tested the MCMC approach on two acoustic reflectivity data sets one synthesized from a CTD cast and the other derived from multichannel seismic reflections. This method finds the solutions faithfully within the significantly narrowed confidence intervals from the provided priors. Combined with a low frequency initial model interpreted from seismic horizons of ISWs, the MCMC method is used to compute the finescale temperature, salinity, acoustic velocity, and density of ISW field. The statistically derived results are equivalent to the conventional linearized inversion method. However, the former provides us the quantified uncertainties of the temperature and salinity along the whole section whilst the latter does not. These results are the first time ISWs have been mapped with sufficient detail for further analysis of their dynamic properties.
Iriana, Windy; Tonokura, Kenichi; Kawasaki, Masahiro; Inoue, Gen; Kusin, Kitso; Limin, Suwido H.
2016-09-01
Evaluation of CO2 flux from peatland soil respiration is important to understand the effect of land use change on the global carbon cycle and climate change and particularly to support carbon emission reduction policies. However, quantitative estimation of emitted CO2 fluxes in Indonesia is constrained by existing field data. Current methods for CO2 measurement are limited by high initial cost, manpower, and the difficulties associated with construction issues. Measurement campaigns were performed using a newly developed nocturnal temperature-inversion trap method, which measures the amount of CO2 trapped beneath the nocturnal inversion layer, in the dry season of 2013 at a drained tropical peatland near Palangkaraya, Central Kalimantan, Indonesia. This method is cost-effective and data processing is easier than other flux estimation methods. We compared CO2 fluxes measured using this method with the published data from the existing eddy covariance and closed chamber methods. The maximum value of our measurement results was 10% lower than maximum value of eddy covariance method and average value was 6% higher than average of chamber method in drained tropical peatlands. In addition, the measurement results shows good correlation with groundwater table. The results of this comparison suggest that this methodology for the CO2 flux measurement is useful for field research in tropical peatlands.
Na, Bing; Lv, Ruihua; Xu, Wenfei; Yu, Pingsheng; Wang, Ke; Fu, Qiang
2007-11-22
Irradiation of ultrahigh molecular weight polyethylene (UHMWPE) with a dose of 150 kGy by an electron beam can effectively increase the entanglement density in the amorphous phase and has little influence on the properties of the crystalline phase, which provides examples to comparatively investigate the role of lamellar coupling and entanglement density in determining the strain-hardening effect in semicrystalline polymers. The strain-hardening modulus, deduced from the Haward plots of true stress-strain curves, is inversely temperature-dependent and has a sharp transition around 65 degrees C that corresponds to the mechanical alphaI-process of the crystalline phase for both nonirradiated and irradiated samples, irrespective of the entanglement density in the amorphous phase. Lamellar coupling takes more effect in determining the strain-hardening behavior before the mechanical alphaI-process is activated. With further increasing temperature, lamellar coupling becomes weaker and the role of the entangled amorphous phase is gradually presented. However, the same temperature dependence of the strain-hardening modulus in both nonirradiated and irradiated samples indicates that the strain-hardening behavior in semicrystalline polymer is mostly determined by lamellar coupling rather than by entanglement density.
International Nuclear Information System (INIS)
Morilhat, P.; Maye, J.-P.; Brendle, E.; Hay, B.
1992-01-01
The solution of an inverse heat conduction problem (estimation of parietal temperature fluctuations inside a pipe from external measurements) using transfer functions is proposed. An analytical method and impulse response technique are studied, compared and tested for a pressurized water reactor (PWR) pipe, in working conditions favourable to thermal striping. The study shows the advantages of thermal stress measurements in comparison with temperature measurements for greater efficiency in the inverse method and gives proof of the greater suitability of the impulse response technique for complex geometries. (author)
Inverse CeO2sbnd Fe2O3 catalyst for superior low-temperature CO conversion efficiency
Luo, Yongming; Chen, Ran; Peng, Wen; Tang, Guangbei; Gao, Xiaoya
2017-09-01
The paper presents a rational design of highly efficient and affordable catalysts for CO oxidation with a low operating temperature. A series of ceria-iron catalysts were inversely built via a co-precipitation method. The catalytic activity of low-temperature CO oxidation was much higher with CeO2-modified Fe2O3 (CeO2sbnd Fe2O3) than with Fe2O3-modified CeO2 (Fe2O3sbnd CeO2). In particular, the 7.5% CeO2sbnd Fe2O3 catalyst had the highest activity, reaching 96.17% CO conversion at just 25 °C. Catalyst characterization was carried out to explore the cause of the significantly different CO conversion efficiencies between the Fe2O3sbnd CeO2 and Fe2O3sbnd CeO2 catalysts. HRTEM showed a significant inhomogeneous phase in 7.5% CeO2sbnd Fe2O3 with small CeO2 nanoparticles highly dispersed on the rod-shaped Fe2O3 surface. Furthermore, the 7.5% CeO2sbnd Fe2O3 composite catalyst exhibited the highest ratios of Fe2+/Fe3+ and Ce3+/Ce4+ as well as the largest pore volume. These properties are believed to benefit the CO conversion in 7.5% CeO2sbnd Fe2O3.
Bahari, R. A.; Abbaspour, R. A.; Pahlavani, P.
2014-10-01
Today, air pollutant is a big challenge for busy and big cities due to its direct effect on both human health and the environment. Tehran, as the capital city of Iran, concludes 12 million people and is one of the most polluted cities in Iran. According to the reports, the main cause of Tehran's pollution is particle matters. The main factors affecting the density and distribution of pollution in Tehran are topography, traffic, and meteorological parameters including wind speed and direction, environment temperature, cloud cover, relative humidity, the sunshine overs a day, the rainfall, pressure, and temperature inversion. To help the urban management of Tehran, in this paper, a novel method is proposed to predicted PM2.5 concentration for upcoming 72 hours. The results show that the proposed model has high capability in predicting PM2.5 concentration and the achieved statistic coefficient of determination (R2) was equal to 0.61-0.79, which indicates the goodness of fit of our proposed model supports the prediction of PM2.5 concentration.
Topographic Evolution of the Sierra Nevada Resolved by Inversion of Low-Temperature Thermochronology
McPhillips, D. F.; Brandon, M. T.
2011-12-01
At present, there are two competing ideas for the topographic evolution of the Sierra Nevada Range. One idea is that the Sierra Nevada was formed as a monocline in the Cretaceous, marking the transition from the Great Valley forearc basin to the west, and a high Nevadaplano plateau to the east, similar to the west flank of the modern Altiplano of the Andes. Both the thermochronologic signature of local relief and the stable isotopic evidence of a topographic rain shadow support this hypothesis. However, a suite of geomorphic observations suggests that the Sierra gained a large fraction of its present elevation as recently as the Pliocene. This recent surface uplift could have been driven by convective removal of in the lower part of the lithosphere and/or by changes in dynamic topography associated with deep subduction of the Farallon plate. Here we present the first comprehensive analysis of low-temperature thermochronology in the Sierra Nevada, which provides a definitive solution, which indicates that both ideas are likely correct. Our analysis is distinguished by three new factors: The first is that we allow for separate evolutions for the local relief and the long-wavelength topography. Second, we use Al-in-Hb paleobarometry to constrain the initial depth of emplacement for the Sierra Nevada plutons. Third, our analysis is tied to a sea-level reference by using the paleo-bathymetric record of the Great Valley basin, where it on-laps the Sierra Nevada batholith. According to our analysis, westward tilting of the Sierra accounts for 2 km of uplift since 20 Ma. Topographic relief increased by a factor of 2. These findings suggest that the Sierra Nevada lost elevation through most of the Tertiary but regained much of its initial elevation following the onset of surface uplift in the Miocene.
Sakami, M.; Lallemand, M.
1994-05-01
The infrared absorption spectra of silicate glasses and boric anhydrid at high temperature are worked out by means of an inverse technique of optimization from the emission spectra. The sample's emission spectral intensities are measured by a Fourier Transform lnfra-Red spectrometer. Specimens are plane parallel slabs which are deposited on a crusible. Their lower face is in contact of the crusible and isothermal but the upper one exchanges heat with the atmosphere by natural convection. In such conditions the glass slabs are submitted to high thermal gradients and the optimization method used is a non-linear constainted iterative method. The resulting spectra are compared to absorption spectra obtained by transmission spectrometry. Les spectres d'absorption infrarouge de verres de silicate et d'anhydride borique portés à haute température sont obtenus par inversion des spectres d'émission au moyen d'une méthode d'optimisation. Les luminances spectrales émises par les échantillons sont mesurées à l'aide d'un spectromètre à transformée de Fourier. Les échantillons sont des lames planes parallèles déposées dans un creuset ; leur surface inférieure est maintenue vers 1 000 K, alors que leur surface supérieure échange sa chaleur à l'air libre par convection naturelle. Dans ces conditions les lames sont soumises à de forts gradients thermiques. En présence de ces gradients une méthode itérative d'optimisation non linéaire contrainte est mise en œuvre. On compare les résultats obtenus aux spectres d'absorption mesurés directement par spectrométrie de transmission.
International Nuclear Information System (INIS)
Sellitto, P.; Del Frate, F.
2014-01-01
Atmospheric temperature profiles are inferred from passive satellite instruments, using thermal infrared or microwave observations. Here we investigate on the feasibility of the retrieval of height resolved temperature information in the ultraviolet spectral region. The temperature dependence of the absorption cross sections of ozone in the Huggins band, in particular in the interval 320–325 nm, is exploited. We carried out a sensitivity analysis and demonstrated that a non-negligible information on the temperature profile can be extracted from this small band. Starting from these results, we developed a neural network inversion algorithm, trained and tested with simulated nadir EnviSat-SCIAMACHY ultraviolet observations. The algorithm is able to retrieve the temperature profile with root mean square errors and biases comparable to existing retrieval schemes that use thermal infrared or microwave observations. This demonstrates, for the first time, the feasibility of temperature profiles retrieval from space-borne instruments operating in the ultraviolet. - Highlights: • A sensitivity analysis and an inversion scheme to retrieve temperature profiles from satellite UV observations (320–325 nm). • The exploitation of the temperature dependence of the absorption cross section of ozone in the Huggins band is proposed. • First demonstration of the feasibility of temperature profiles retrieval from satellite UV observations. • RMSEs and biases comparable with more established techniques involving TIR and MW observations
Nizam Uddin
2013-01-01
Inverse interpolation is the process of finding the values of the argument corresponding to a given value of the function when the latter is intermediate between two tabulated values. The finite differences are differences between the values of the function or the difference between the past differences. Finite differences are forward difference, backward difference and divide difference. Temperature, concentration of substrate, concentration of enzyme and other factors are affected the rate ...
International Nuclear Information System (INIS)
Golbahar Haghighi, M.R.; Eghtesad, M.; Necsulescu, D.S.; Malekzadeh, P.
2010-01-01
As a first endeavor, an approach for the two- and three-dimensional temperature control of functionally graded (FG) plates by using the inverse solution and the proportional-differential (PD) controller is provided. For this purpose, firstly, having the desired temperatures at different locations and times, heat fluxes at the boundaries of the plates are estimated by inverse solution techniques offline. Then, the estimated heat fluxes as feedforward control inputs are combined with a PD controller to introduce a hybrid feedforward-feedback control input to the FG domain in the presence of disturbance and noise. In order to show the efficiency and accuracy of the proposed (inverse + PD) controller in two- and three-dimensional domains, different distinct examples, which include different boundary conditions, material properties and disturbance sources are presented. It is shown that the presented approach can adjust heat fluxes for control of the temperature accurately; also, the PD controller gains do not need to be re-adjusted for different problems.
Aires, F.; Rossow, W. B.; Scott, N. A.; Chedin, A.; Hansen, James E. (Technical Monitor)
2001-01-01
A fast temperature water vapor and ozone atmospheric profile retrieval algorithm is developed for the high spectral resolution Infrared Atmospheric Sounding Interferometer (IASI) space-borne instrument. Compression and de-noising of IASI observations are performed using Principal Component Analysis. This preprocessing methodology also allows, for a fast pattern recognition in a climatological data set to obtain a first guess. Then, a neural network using first guess information is developed to retrieve simultaneously temperature, water vapor and ozone atmospheric profiles. The performance of the resulting fast and accurate inverse model is evaluated with a large diversified data set of radiosondes atmospheres including rare events.
Digital Repository Service at National Institute of Oceanography (India)
Muraleedharan, P.M.; Mohankumar, K.; Sivakumar, K.U.
The thermal inversion characteristics during active and break cycles of two consecutive and contrasting monsoon years were studied using GPS radiosonde profiles in Goa (15 degrees 46′ N; 73 degrees 08′ E), located on the west coast of India...
International Nuclear Information System (INIS)
Aboanber, A E; Nahla, A A
2002-01-01
A method based on the Pade approximations is applied to the solution of the point kinetics equations with a time varying reactivity. The technique consists of treating explicitly the roots of the inhour formula. A significant improvement has been observed by treating explicitly the most dominant roots of the inhour equation, which usually would make the Pade approximation inaccurate. Also the analytical inversion method which permits a fast inversion of polynomials of the point kinetics matrix is applied to the Pade approximations. Results are presented for several cases of Pade approximations using various options of the method with different types of reactivity. The formalism is applicable equally well to non-linear problems, where the reactivity depends on the neutron density through temperature feedback. It was evident that the presented method is particularly good for cases in which the reactivity can be represented by a series of steps and performed quite well for more general cases
Shen, F.; Khodadadi, J. M.
1993-01-01
In order to determine the thermal diffusivity of materials at high temperatures, a two-step extended flash technique, which is applicable to levitated spherical samples, is proposed. The containerless flash method is modeled as an axisymmetric transient conduction heat transfer problem within the sphere subjected to a radiative boundary condition on its surface. The problem of nonlinearity which arises from the radiative heat transfer boundary condition is solved by replacing it with the measured time-dependent surface temperature data, thus giving rise to an 'Inverse Analysis'. Upon obtaining the analytic solution for the temperature field, the determination of the thermal diffusivity turns into a minimization problem, whereby the difference between the actual surface boundary condition and the analytic solution is minimized. In performing the proposed experiments, there is a need to undertake a cool-down experiment which should be governed by the lumped parameter analysis.
International Nuclear Information System (INIS)
Kubo, S; Uchida, K; Ishizaka, T; Ioka, S
2008-01-01
It is important to reduce the thermal stresses for managing and extending the lives of pipes in plants. In this problem, heat conduction, elastic deformation, heat transfer, liquid flow should be considered, and therefore the problem is of a multidisciplinary nature. An inverse method was proposed by the present authors for determining the optimum thermal load history which reduced transient thermal stress considering the multidisciplinary physics. But the obtained solution had a problem that the temperature increasing rate of inner surface of the pipe was discontinuous at the end time of heat up. In this study we introduce temperature history functions that ensure the continuity of the temperature increasing rate. The multidisciplinary complex problem is decomposed into a heat conduction problem, a heat transfer problem, and a thermal stress problem. An analytical solution of the temperature distribution of radial thickness and thermal hoop stress distribution is obtained. The maximum tensile and compressive hoop stresses are minimized for the case where inner surface temperature T s (t) is expressed in terms of the 4th order polynomial function of time t. Finally, from the temperature distributions, the optimum fluid temperature history is obtained for reducing the thermal stresses.
Dimitrov, Marin
2014-01-01
We coupled a radiative transfer model and a soil hydrologic model (HYDRUS 1D) with an optimization routine to derive soil hydraulic parameters, surface roughness, and soil moisture of a tilled bare soil plot using measured brightness temperatures at 1.4 GHz (L-band), rainfall, and potential soil evaporation. The robustness of the approach was evaluated using five 28-d data sets representing different meteorological conditions. We considered two soil hydraulic property models: the unimodal Mualem-van Genuchten and the bimodal model of Durner. Microwave radiative transfer was modeled by three different approaches: the Fresnel equation with depth-averaged dielectric permittivity of either 2-or 5-cm-thick surface layers and a coherent radiative transfer model (CRTM) that accounts for vertical gradients in dielectric permittivity. Brightness temperatures simulated by the CRTM and the 2-cm-layer Fresnel model fitted well to the measured ones. L-band brightness temperatures are therefore related to the dielectric permittivity and soil moisture in a 2-cm-thick surface layer. The surface roughness parameter that was derived from brightness temperatures using inverse modeling was similar to direct estimates from laser profiler measurements. The laboratory-derived water retention curve was bimodal and could be retrieved consistently for the different periods from brightness temperatures using inverse modeling. A unimodal soil hydraulic property function underestimated the hydraulic conductivity near saturation. Surface soil moisture contents simulated using retrieved soil hydraulic parameters were compared with in situ measurements. Depth-specific calibration relations were essential to derive soil moisture from near-surface installed sensors. © Soil Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA.
International Nuclear Information System (INIS)
Namatame, Hirofumi; Taniguchi, Masaki
1994-01-01
Photoelectron spectroscopy is regarded as the most powerful means since it can measure almost perfectly the occupied electron state. On the other hand, inverse photoelectron spectroscopy is the technique for measuring unoccupied electron state by using the inverse process of photoelectron spectroscopy, and in principle, the similar experiment to photoelectron spectroscopy becomes feasible. The development of the experimental technology for inverse photoelectron spectroscopy has been carried out energetically by many research groups so far. At present, the heightening of resolution of inverse photoelectron spectroscopy, the development of inverse photoelectron spectroscope in which light energy is variable and so on are carried out. But the inverse photoelectron spectroscope for vacuum ultraviolet region is not on the market. In this report, the principle of inverse photoelectron spectroscopy and the present state of the spectroscope are described, and the direction of the development hereafter is groped. As the experimental equipment, electron guns, light detectors and so on are explained. As the examples of the experiment, the inverse photoelectron spectroscopy of semimagnetic semiconductors and resonance inverse photoelectron spectroscopy are reported. (K.I.)
Gatlin, J. A.; Englar, T. S.
1976-01-01
Generation of vertical temperatures profiles from remotely sensed atmospheric radiance data is described as an analogous communications system. The radiative transport characteristics of the atmosphere encodes the continuous temperature profile into an 'n' element vector where 'n' is the number of channels in the satellite instrument. The temperature profile is a message transmitted from station A to station B and the link is the satellite instrument. At station B the decoder reproduces a continuous function which is the best estimate of the message encoded at station A. It is shown that the decoder must operate in a tuned mode where the parameters used in the encoder precisely determine the decoder parameters, and that the characteristics of the total message block must be given by a set of decoder constraints
Czech Academy of Sciences Publication Activity Database
Majorowicz, J.; Šafanda, Jan; Skinner, W.
2002-01-01
Roč. 107, B10 (2002), s. ETG6 1-12 ISSN 0148-0227 Institutional research plan: CEZ:AV0Z3012916 Keywords : Canada climate warming * borehole temperature * geothermics Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.245, year: 2002
Czech Academy of Sciences Publication Activity Database
Majorowicz, J. A.; Skinner, W. R.; Šafanda, Jan
2005-01-01
Roč. 162, č. 2 (2005), s. 109-128 ISSN 0033-4553 Institutional research plan: CEZ:AV0Z30120515 Keywords : global warming * regional climate variability and change * borehole temperatures Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.975, year: 2005
Ma, Weiqiang; Huang, Fangfang; Ma, Yaoming; Hu, Zeyong; Zhong, Lei
2017-04-01
Time series of MODIS land surface temperature (LST) and normalized difference vegetation index (NDVI) products, combined with digital elevation model (DEM) and meteorological data from 2001 to 2012, were used to map the spatial distribution of monthly mean air temperature over the Northern Tibetan Plateau (NTP). A time series analysis and a regression analysis of monthly mean land surface temperature (Ts) and air temperature (Ta) were conducted using ordinary linear regression (OLR) and geographical weighted regression (GWR) methods. The analyses showed that the GWR method, which considers MODIS LST, NDVI and elevation as independent variables, yielded much better results (Adjusted R2 > 0.79, and root mean square error (RMSE) between 0.51 °C and 1.12 °C) associated with estimating Ta compared to those of the OLR method (Adjusted R2 = 0.40 0.78, and RMSE=1.60 4.38 °C). In addition, some characteristics of the spatial distribution of monthly Ta and the difference (dT) between the surface and air temperature are as follows. According to the analysis of the 0 °C and 10 °C isothermals, Ta values over the NTP at elevations of 4000 5000 meters were over 10 °C in the summer (from May to October), and Ta values at an elevation of 3200 meters dropped below 0 °C in the winter (from November to April). Ta exhibited an increasing trend from northwest to southeast. Except in the southeastern area of the NTP, dT values in other areas were all larger than 0 °C in the winter.
Ingram, WT
2012-01-01
Inverse limits provide a powerful tool for constructing complicated spaces from simple ones. They also turn the study of a dynamical system consisting of a space and a self-map into a study of a (likely more complicated) space and a self-homeomorphism. In four chapters along with an appendix containing background material the authors develop the theory of inverse limits. The book begins with an introduction through inverse limits on [0,1] before moving to a general treatment of the subject. Special topics in continuum theory complete the book. Although it is not a book on dynamics, the influen
Nahon, Kimberly J; Boon, Mariëtte R; Doornink, Fleur; Jazet, Ingrid M; Rensen, Patrick C N; Abreu-Vieira, Gustavo
2017-10-01
It is colloquially stated that body size plays a role in the human response to cold, but the magnitude and details of this interaction are unclear. To explore the inherent influence of body size on cold-exposed metabolism, we investigated the relation between body composition and resting metabolic rate in humans at thermoneutrality and during cooling within the nonshivering thermogenesis range. Body composition and resting energy expenditure were measured in 20 lean and 20 overweight men at thermoneutrality and during individualized cold exposure. Metabolic rates as a function of ambient temperature were investigated considering the variability in body mass and composition. We observed an inverse relationship between body size and the lower critical temperature (LCT), i.e. the threshold where thermoneutrality ends and cold activates thermogenesis. LCT was higher in lean than overweight subjects (22.1 ± 0.6 vs 19.5 ± 0.5°C, p lean and overweight (100 ± 4 vs 97 ± 3kcal/°C/day respectively, p = 0.45). Overweight individuals had higher basal metabolic rate (BMR) explained mostly by the higher lean mass, and lower cold-induced thermogenesis (CIT) per degree of cold exposure. Below thermoneutrality, energy expenditure did not scale to lean body mass. Overweight subjects had lower heat loss per body surface area (44.7 ± 1.3 vs 54.7 ± 2.3kcal/°C/m 2 /day, p lean mass rather than a change in whole-body conductance. Thus, larger individuals with higher lean mass need to be exposed to colder temperatures to activate CIT, not because of increased insulation, but because of a higher basal heat generation. Our study suggests that the distinct effects of body size and composition on energy expenditure should be taken in account when exploring the metabolism of humans exposed to cold. Copyright © 2017 Elsevier Ltd. All rights reserved.
Sheehan, Anne F.; Solomon, Sean C.
1991-01-01
Measurements were carried out for SS-S differential travel time residuals for nearly 500 paths crossing the northern Mid-Atlantic Ridge, assuming that the residuals are dominated by contributions from the upper mantle near the surface bounce point of the reflected phase SS. Results indicate that the SS-S travel time residuals decrease linearly with square root of age, to an age of 80-100 Ma, in general agreement with the plate cooling model. A joint inversion was formulated of travel time residuals and geoid and bathymetric anomalies for lateral variation in the upper mantle temperature and composition. The preferred inversion solutions were found to have variations in upper mantle temperature along the Mid-Atlantic Ridge of about 100 K. It was calculated that, for a constant bulk composition, such a temperature variation would produce about a 7-km variation in crustal thickness, larger than is generally observed.
International Nuclear Information System (INIS)
İlter, Zülfiye; Demir, Abdullah; Kaya, İsmet
2016-01-01
Highlights: • Thermodynamic of methacrylate-co-styrene polymers were studied by the inverse gas chromatography. • The sorption parameters of polymer-solute systems were determined under glass transition temperature of polymers. • The solubility parameter (δ 2 ) of the polymer was obtained from the slope and intercepts. • Flory-Huggins interaction parameter (χ 12 ∞ ) were determined for polymer-solute systems. - Abstract: In this study, some thermodynamic properties of poly(7-methoxy-2-acetylbenzofurane methyl methacrylate-co-styrene) Poly(MABMM-co-St) and poly(2-acetylbenzofurane methyl methacrylate-co-styrene) Poly(ABMM-co-St) were studied by the inverse gas chromatography (IGC) technique. The retention times (t r ) of selected organic probes were determined from the interactions with Poly(MABMM-co-St) and Poly(ABMM-co-St) of four groups of solvents with different chemical natures and polarities. Then, specific volume (V g 0 ) values of probes were calculated at different column temperatures. The glass transition temperatures (T g ) of Poly(MABMM-co-St) and Poly(ABMM-co-St) were found as 393, 413 K from inverse gas chromatography measurements, respectively. Under the glass transition temperatures adsorption heat (ΔH a ) and above the glass transition molar heat (ΔH 1 S ), free energies (ΔG 1 S ) and entropies (ΔS 1 S ) belonging to sorption for every probe were calculated from inverse gas chromatography measurements. The partial molar heat (ΔH 1 ∞ ), partial molar free energy (ΔG 1 ∞ ), Flory-Huggins interaction parameter (χ 12 ∞ ) and weight fraction activity coefficient (a 1 /w 1 ) ∞ , values for infinite dilute solutions were calculated for polymer-probe systems. The solubility parameter (δ 2 ) of the polymer was obtained from the slope and intercepts of Flory-Huggins interaction parameter (χ 12 ∞ ) graphs with solubility parameters (δ 1 ) of probes.
Digital Repository Service at National Institute of Oceanography (India)
Pankajakshan, T.; Ghosh, A.K.; Pattanaik, J.; Ratnakaran, L.
bucket temperature is not reported, it is suggested to take the 5m XBT-temperature(5-XT) as XST. This extrapolation procedure of 5-XT as XST using the XBT-CTD controlled data set of Thadathil et al. 1998 has been found valid. Surface layer temperature...
Inverse problems of geophysics
International Nuclear Information System (INIS)
Yanovskaya, T.B.
2003-07-01
This report gives an overview and the mathematical formulation of geophysical inverse problems. General principles of statistical estimation are explained. The maximum likelihood and least square fit methods, the Backus-Gilbert method and general approaches for solving inverse problems are discussed. General formulations of linearized inverse problems, singular value decomposition and properties of pseudo-inverse solutions are given
Directory of Open Access Journals (Sweden)
Halis Aygün
2008-01-01
Full Text Available We introduce definitions of fuzzy inverse compactness, fuzzy inverse countable compactness, and fuzzy inverse Lindelöfness on arbitrary -fuzzy sets in -fuzzy topological spaces. We prove that the proposed definitions are good extensions of the corresponding concepts in ordinary topology and obtain different characterizations of fuzzy inverse compactness.
Bergbreiter, David E.; Mijalis, Alexander J.; Fu, Hui
2012-01-01
Reversible polymer dehydration and precipitation from water due to the unfavorable entropy of hydration is examined using a melting-point apparatus. The thermoresponsive lower critical solution temperature (LCST) behavior of poly(N-isopropylacrylamide) (PNIPAM) is responsible for these effects. An experiment is described that allows students to…
Directory of Open Access Journals (Sweden)
G. Polt
2015-10-01
Full Text Available In-situ X-ray diffraction was applied to isotactic polypropylene with a high volume fraction of α-phase (α-iPP while it has been compressed at temperatures below and above its glass transition temperature Tg. The diffraction patterns were evaluated by the Multi-reflection X-ray Profile Analysis (MXPA method, revealing microstructural parameters such as the density of dislocations and the size of coherently scattering domains (CSD-size. A significant difference in the development of the dislocation density was found compared to compression at temperatures above Tg, pointing at a different plastic deformation mechanism at these temperatures. Based on the individual evolutions of the dislocation density and CSD-size observed as a function of compressive strain, suggestions for the deformation mechanisms occurring below and above Tg are made.
Directory of Open Access Journals (Sweden)
P. Bourgain
2013-04-01
Full Text Available Between 2008 and 2010, the Arctic Oscillation index over Arctic regions shifted from positive values corresponding to more cyclonic conditions prevailing during the 4th International Polar Year (IPY period (2007–2008 to extremely negative values corresponding to strong anticyclonic conditions in 2010. In this context, we investigated the recent large-scale evolution of the upper western Arctic Ocean, based on temperature and salinity summertime observations collected during icebreaker campaigns and from ice-tethered profilers (ITPs drifting across the region in 2008 and 2010. Particularly, we focused on (1 the freshwater content which was extensively studied during previous years, (2 the near-surface temperature maximum due to incoming solar radiation, and (3 the water masses advected from the Pacific Ocean into the Arctic Ocean. The observations revealed a freshwater content change in the Canadian Basin during this time period. South of 80° N, the freshwater content increased, while north of 80° N, less freshening occurred in 2010 compared to 2008. This was more likely due to the strong anticyclonicity characteristic of a low AO index mode that enhanced both a wind-generated Ekman pumping in the Beaufort Gyre and a possible diversion of the Siberian River runoff toward the Eurasian Basin at the same time. The near-surface temperature maximum due to incoming solar radiation was almost 1 °C colder in the southern Canada Basin (south of 75° N in 2010 compared to 2008, which contrasted with the positive trend observed during previous years. This was more likely due to higher summer sea ice concentration in 2010 compared to 2008 in that region, and surface albedo feedback reflecting more sun radiation back in space. The Pacific water (PaW was also subjected to strong spatial and temporal variability between 2008 and 2010. In the Canada Basin, both summer and winter PaW signatures were stronger between 75° N and 80° N. This was more likely
Superconductivity in Pb inverse opal
International Nuclear Information System (INIS)
Aliev, Ali E.; Lee, Sergey B.; Zakhidov, Anvar A.; Baughman, Ray H.
2007-01-01
Type-II superconducting behavior was observed in highly periodic three-dimensional lead inverse opal prepared by infiltration of melted Pb in blue (D = 160 nm), green (D = 220 nm) and red (D = 300 nm) opals and followed by the extraction of the SiO 2 spheres by chemical etching. The onset of a broad phase transition (ΔT = 0.3 K) was shifted from T c = 7.196 K for bulk Pb to T c = 7.325 K. The upper critical field H c2 (3150 Oe) measured from high-field hysteresis loops exceeds the critical field for bulk lead (803 Oe) fourfold. Two well resolved peaks observed in the hysteresis loops were ascribed to flux penetration into the cylindrical void space that can be found in inverse opal structure and into the periodic structure of Pb nanoparticles. The red inverse opal shows pronounced oscillations of magnetic moment in the mixed state at low temperatures, T 0.9T c has been observed for all of the samples studied. The magnetic field periodicity of resistivity modulation is in good agreement with the lattice parameter of the inverse opal structure. We attribute the failure to observe pronounced modulation in magneto-resistive measurement to difficulties in the precision orientation of the sample along the magnetic field
Directory of Open Access Journals (Sweden)
Abedini Reza
2012-01-01
Full Text Available In this study, asymmetric pure CA and CA/ TiO2 composite membranes were prepared via phase inversion by dispersing TiO2 nanopaticles in the CA casting solutions induced by immersion precipitation in water coagulation bath. TiO2 nanoparticles, which were synthesized by the sonochemical method, were added into the casting solution with different concentrations. Effects of TiO2 nanoparticles concentration (0 wt. %, 5wt.%, 10wt.%, 15wt.%, 20wt.% and 25wt.% and coagulation bath temperature (CBT= 25°C, 50°C and 75°C on morphology, thermal stability and pure water flux (PWF of the prepared membranes were studied and discussed. Increasing TiO2 concentration in the casting solution film along with higher CBT resulted in increasing the membrane thickness, water content (WC, membrane porosity and pure water flux (PWF, also these changes facilitate macrovoids formation. Thermal gravimetric analysis (TGA shows that thermal stability of the composite membranes were improved by the addition of TiO2 nanopaticles. Also TGA results indicated that increasing CBT in each TiO2 concentration leads to the decreasing of decomposition temperature (Td of hybrid membranes.
International Nuclear Information System (INIS)
Rogers, Justin C.; Apai, Daniel; Lopez-Morales, Mercedes; Sing, David K.; Burrows, Adam
2009-01-01
We report the detection in Ks-band of the secondary eclipse of the hot Jupiter CoRoT-1b from time series photometry with the ARC 3.5 m telescope at Apache Point Observatory. The eclipse shows a depth of 0.336 ± 0.042% and is centered at phase 0.5022 +0.0023 -0.0027 , consistent with a zero eccentricity orbit (e cos ω = 0.0035 +0.0036 -0.0042 ). We perform the first optical to near-infrared multi-band photometric analysis of an exoplanet's atmosphere and constrain the reflected and thermal emissions by combining our result with the recent 0.6, 0.71, and 2.09 μm secondary eclipse detections by Snellen et al., Gillon et al., and Alonso et al. Comparing the multi-wavelength detections to state-of-the-art radiative-convective chemical-equilibrium atmosphere models, we find the near-infrared fluxes difficult to reproduce. The closest blackbody-based and physical models provide the following atmosphere parameters: a temperature T = 2460 +80 -160 K; a very low Bond albedo A B = 0.000 +0.081 -0.000 ; and an energy redistribution parameter P n = 0.1, indicating a small but nonzero amount of heat transfer from the day to nightside. The best physical model suggests a thermal inversion layer with an extra optical absorber of opacity κ e = 0.05 cm 2 g -1 , placed near the 0.1 bar atmospheric pressure level. This inversion layer is located 10 times deeper in the atmosphere than the absorbers used in models to fit mid-infrared Spitzer detections of other irradiated hot Jupiters.
Population inversion in recombining hydrogen plasma
International Nuclear Information System (INIS)
Furukane, Utaro; Yokota, Toshiaki; Oda, Toshiatsu.
1978-11-01
The collisional-radiative model is applied to a recombining hydrogen plasma in order to investigate the plasma condition in which the population inversion between the energy levels of hydrogen can be generated. The population inversion is expected in a plasma where the three body recombination has a large contribution to the recombining processes and the effective recombination rate is beyond a certain value for a given electron density and temperature. Calculated results are presented in figures and tables. (author)
Inversion of GPS meteorology data
Directory of Open Access Journals (Sweden)
K. Hocke
Full Text Available The GPS meteorology (GPS/MET experiment, led by the Universities Corporation for Atmospheric Research (UCAR, consists of a GPS receiver aboard a low earth orbit (LEO satellite which was launched on 3 April 1995. During a radio occultation the LEO satellite rises or sets relative to one of the 24 GPS satellites at the Earth's horizon. Thereby the atmospheric layers are successively sounded by radio waves which propagate from the GPS satellite to the LEO satellite. From the observed phase path increases, which are due to refraction of the radio waves by the ionosphere and the neutral atmosphere, the atmospheric parameter refractivity, density, pressure and temperature are calculated with high accuracy and resolution (0.5–1.5 km. In the present study, practical aspects of the GPS/MET data analysis are discussed. The retrieval is based on the Abelian integral inversion of the atmospheric bending angle profile into the refractivity index profile. The problem of the upper boundary condition of the Abelian integral is described by examples. The statistical optimization approach which is applied to the data above 40 km and the use of topside bending angle profiles from model atmospheres stabilize the inversion. The retrieved temperature profiles are compared with corresponding profiles which have already been calculated by scientists of UCAR and Jet Propulsion Laboratory (JPL, using Abelian integral inversion too. The comparison shows that in some cases large differences occur (5 K and more. This is probably due to different treatment of the upper boundary condition, data runaways and noise. Several temperature profiles with wavelike structures at tropospheric and stratospheric heights are shown. While the periodic structures at upper stratospheric heights could be caused by residual errors of the ionospheric correction method, the periodic temperature fluctuations at heights below 30 km are most likely caused by atmospheric waves (vertically
Inverse Kinematics using Quaternions
DEFF Research Database (Denmark)
Henriksen, Knud; Erleben, Kenny; Engell-Nørregård, Morten
In this project I describe the status of inverse kinematics research, with the focus firmly on the methods that solve the core problem. An overview of the different methods are presented Three common methods used in inverse kinematics computation have been chosen as subject for closer inspection....
Inverse logarithmic potential problem
Cherednichenko, V G
1996-01-01
The Inverse and Ill-Posed Problems Series is a series of monographs publishing postgraduate level information on inverse and ill-posed problems for an international readership of professional scientists and researchers. The series aims to publish works which involve both theory and applications in, e.g., physics, medicine, geophysics, acoustics, electrodynamics, tomography, and ecology.
Inverse transient thermoelastic deformations in thin circular plates
Indian Academy of Sciences (India)
Bessel's functions with the help of the integral transform technique. Thermoelastic deformations are discussed with the help of temperature and are illustrated numer- ically. Keywords. Inverse transient; thermoelastic deformation. 1. Introduction. The inverse thermoelastic problem consists of determination of the temperature, ...
International Nuclear Information System (INIS)
Burkhard, N.R.
1979-01-01
The gravity inversion code applies stabilized linear inverse theory to determine the topography of a subsurface density anomaly from Bouguer gravity data. The gravity inversion program consists of four source codes: SEARCH, TREND, INVERT, and AVERAGE. TREND and INVERT are used iteratively to converge on a solution. SEARCH forms the input gravity data files for Nevada Test Site data. AVERAGE performs a covariance analysis on the solution. This document describes the necessary input files and the proper operation of the code. 2 figures, 2 tables
Sharp spatially constrained inversion
DEFF Research Database (Denmark)
Vignoli, Giulio G.; Fiandaca, Gianluca G.; Christiansen, Anders Vest C A.V.C.
2013-01-01
We present sharp reconstruction of multi-layer models using a spatially constrained inversion with minimum gradient support regularization. In particular, its application to airborne electromagnetic data is discussed. Airborne surveys produce extremely large datasets, traditionally inverted...... by using smoothly varying 1D models. Smoothness is a result of the regularization constraints applied to address the inversion ill-posedness. The standard Occam-type regularized multi-layer inversion produces results where boundaries between layers are smeared. The sharp regularization overcomes...... inversions are compared against classical smooth results and available boreholes. With the focusing approach, the obtained blocky results agree with the underlying geology and allow for easier interpretation by the end-user....
International Nuclear Information System (INIS)
Rosenwald, J.-C.
2008-01-01
The lecture addressed the following topics: Optimizing radiotherapy dose distribution; IMRT contributes to optimization of energy deposition; Inverse vs direct planning; Main steps of IMRT; Background of inverse planning; General principle of inverse planning; The 3 main components of IMRT inverse planning; The simplest cost function (deviation from prescribed dose); The driving variable : the beamlet intensity; Minimizing a 'cost function' (or 'objective function') - the walker (or skier) analogy; Application to IMRT optimization (the gradient method); The gradient method - discussion; The simulated annealing method; The optimization criteria - discussion; Hard and soft constraints; Dose volume constraints; Typical user interface for definition of optimization criteria; Biological constraints (Equivalent Uniform Dose); The result of the optimization process; Semi-automatic solutions for IMRT; Generalisation of the optimization problem; Driving and driven variables used in RT optimization; Towards multi-criteria optimization; and Conclusions for the optimization phase. (P.A.)
Inverse problem in hydrogeology
Carrera, Jesús; Alcolea, Andrés; Medina, Agustín; Hidalgo, Juan; Slooten, Luit J.
2005-03-01
The state of the groundwater inverse problem is synthesized. Emphasis is placed on aquifer characterization, where modelers have to deal with conceptual model uncertainty (notably spatial and temporal variability), scale dependence, many types of unknown parameters (transmissivity, recharge, boundary conditions, etc.), nonlinearity, and often low sensitivity of state variables (typically heads and concentrations) to aquifer properties. Because of these difficulties, calibration cannot be separated from the modeling process, as it is sometimes done in other fields. Instead, it should be viewed as one step in the process of understanding aquifer behavior. In fact, it is shown that actual parameter estimation methods do not differ from each other in the essence, though they may differ in the computational details. It is argued that there is ample room for improvement in groundwater inversion: development of user-friendly codes, accommodation of variability through geostatistics, incorporation of geological information and different types of data (temperature, occurrence and concentration of isotopes, age, etc.), proper accounting of uncertainty, etc. Despite this, even with existing codes, automatic calibration facilitates enormously the task of modeling. Therefore, it is contended that its use should become standard practice. L'état du problème inverse des eaux souterraines est synthétisé. L'accent est placé sur la caractérisation de l'aquifère, où les modélisateurs doivent jouer avec l'incertitude des modèles conceptuels (notamment la variabilité spatiale et temporelle), les facteurs d'échelle, plusieurs inconnues sur différents paramètres (transmissivité, recharge, conditions aux limites, etc.), la non linéarité, et souvent la sensibilité de plusieurs variables d'état (charges hydrauliques, concentrations) des propriétés de l'aquifère. A cause de ces difficultés, le calibrage ne peut êtreséparé du processus de modélisation, comme c'est le
Submucous Myoma Induces Uterine Inversion
Directory of Open Access Journals (Sweden)
Yu-Li Chen
2006-06-01
Conclusion: Nonpuerperal inversion of the uterus is rarely encountered by gynecologists. Diagnosis of uterine inversion is often not easy and imaging studies might be helpful. Surgical treatment is the method of choice in nonpuerperal uterine inversion.
Ramig, Keith; Subramaniam, Gopal; Karimi, Sasan; Szalda, David J; Ko, Allen; Lam, Aaron; Li, Jeffrey; Coaderaj, Ani; Cavdar, Leyla; Bogdan, Lukasz; Kwon, Kitae; Greer, Edyta M
2016-04-15
A series of 2,4-disubstituted 1H-1-benzazepines, 2a-d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The conformational inversion (ring-flip) and nitrogen-atom inversion (N-inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-inversion. When the nitrogen-atom substituent was alkyl, as in 2a-c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high energy barrier to N-inversion and a low barrier to ring-flip. In these N-unsubstituted compounds, it was found computationally that the lowest-energy stereodynamic process was ring-flip coupled with N-inversion, as N-inversion alone had a much higher energy barrier.
Inversion layer thermopower in high magnetic field
Energy Technology Data Exchange (ETDEWEB)
Girvin, S.M.; Jonson, M.
1982-11-20
The authors calculate the thermopower of an ideal two-dimensional electron gas (inversion layer) in a quantising magnetic field. They find that the thermopower is a universal function of the reduced temperature which has a novel dependence on the chemical potential.
Inverse scale space decomposition
DEFF Research Database (Denmark)
Schmidt, Marie Foged; Benning, Martin; Schönlieb, Carola-Bibiane
2018-01-01
We investigate the inverse scale space flow as a decomposition method for decomposing data into generalised singular vectors. We show that the inverse scale space flow, based on convex and even and positively one-homogeneous regularisation functionals, can decompose data represented...... by the application of a forward operator to a linear combination of generalised singular vectors into its individual singular vectors. We verify that for this decomposition to hold true, two additional conditions on the singular vectors are sufficient: orthogonality in the data space and inclusion of partial sums...... of the subgradients of the singular vectors in the subdifferential of the regularisation functional at zero. We also address the converse question of when the inverse scale space flow returns a generalised singular vector given that the initial data is arbitrary (and therefore not necessarily in the range...
Inversion assuming weak scattering
DEFF Research Database (Denmark)
Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus
2013-01-01
due to the complex nature of the field. A method based on linear inversion is employed to infer information about the statistical properties of the scattering field from the obtained cross-spectral matrix. A synthetic example based on an active high-frequency sonar demonstrates that the proposed...
Broekhuis, H.
2005-01-01
This article aims at reformulating in more current terms Hoekstra and Mulder’s (1990) analysis of the Locative Inversion (LI) construction. The new proposal is crucially based on the assumption that Small Clause (SC) predicates agree with their external argument in phi-features, which may be
Bayesian seismic AVO inversion
Energy Technology Data Exchange (ETDEWEB)
Buland, Arild
2002-07-01
A new linearized AVO inversion technique is developed in a Bayesian framework. The objective is to obtain posterior distributions for P-wave velocity, S-wave velocity and density. Distributions for other elastic parameters can also be assessed, for example acoustic impedance, shear impedance and P-wave to S-wave velocity ratio. The inversion algorithm is based on the convolutional model and a linearized weak contrast approximation of the Zoeppritz equation. The solution is represented by a Gaussian posterior distribution with explicit expressions for the posterior expectation and covariance, hence exact prediction intervals for the inverted parameters can be computed under the specified model. The explicit analytical form of the posterior distribution provides a computationally fast inversion method. Tests on synthetic data show that all inverted parameters were almost perfectly retrieved when the noise approached zero. With realistic noise levels, acoustic impedance was the best determined parameter, while the inversion provided practically no information about the density. The inversion algorithm has also been tested on a real 3-D dataset from the Sleipner Field. The results show good agreement with well logs but the uncertainty is high. The stochastic model includes uncertainties of both the elastic parameters, the wavelet and the seismic and well log data. The posterior distribution is explored by Markov chain Monte Carlo simulation using the Gibbs sampler algorithm. The inversion algorithm has been tested on a seismic line from the Heidrun Field with two wells located on the line. The uncertainty of the estimated wavelet is low. In the Heidrun examples the effect of including uncertainty of the wavelet and the noise level was marginal with respect to the AVO inversion results. We have developed a 3-D linearized AVO inversion method with spatially coupled model parameters where the objective is to obtain posterior distributions for P-wave velocity, S
Energy Technology Data Exchange (ETDEWEB)
Shin, Chang Soo; Park, Keun Pil [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of); Suh, Jung Hee; Hyun, Byung Koo; Shin, Sung Ryul [Seoul National University, Seoul (Korea, Republic of)
1995-12-01
The seismic reflection exploration technique which is one of the geophysical methods for oil exploration became effectively to image the subsurface structure with rapid development of computer. However, the imagining of subsurface based on the conventional data processing is almost impossible to obtain the information on physical properties of the subsurface such as velocity and density. Since seismic data are implicitly function of velocities of subsurface, it is necessary to develop the inversion method that can delineate the velocity structure using seismic topography and waveform inversion. As a tool to perform seismic inversion, seismic forward modeling program using ray tracing should be developed. In this study, we have developed the algorithm that calculate the travel time of the complex geologic structure using shooting ray tracing by subdividing the geologic model into blocky structure having the constant velocity. With the travel time calculation, the partial derivatives of travel time can be calculated efficiently without difficulties. Since the current ray tracing technique has a limitation to calculate the travel times for extremely complex geologic model, our aim in the future is to develop the powerful ray tracer using the finite element technique. After applying the pseudo waveform inversion to the seismic data of Korea offshore, we can obtain the subsurface velocity model and use the result in bring up the quality of the seismic data processing. If conventional seismic data processing and seismic interpretation are linked with this inversion technique, the high quality of seismic data processing can be expected to image the structure of the subsurface. Future research area is to develop the powerful ray tracer of ray tracing which can calculate the travel times for the extremely complex geologic model. (author). 39 refs., 32 figs., 2 tabs.
Calculation of the inverse data space via sparse inversion
Saragiotis, Christos
2011-01-01
The inverse data space provides a natural separation of primaries and surface-related multiples, as the surface multiples map onto the area around the origin while the primaries map elsewhere. However, the calculation of the inverse data is far from trivial as theory requires infinite time and offset recording. Furthermore regularization issues arise during inversion. We perform the inversion by minimizing the least-squares norm of the misfit function by constraining the $ell_1$ norm of the solution, being the inverse data space. In this way a sparse inversion approach is obtained. We show results on field data with an application to surface multiple removal.
Understanding the inverse magnetocaloric effect in antiferro- and ferrimagnetic arrangements
International Nuclear Information System (INIS)
Von Ranke, P J; De Oliveira, N A; Alho, B P; Plaza, E J R; De Sousa, V S R; Caron, L; Reis, M S
2009-01-01
The inverse magnetocaloric effect occurs when a magnetic material cools down under applied magnetic field in an adiabatic process. Although the existence of the inverse magnetocaloric effect was recently reported experimentally, a theoretical microscopic description is almost nonexistent. In this paper we theoretically describe the inverse magnetocaloric effect in antiferro- and ferrimagnetic systems. The inverse magnetocaloric effects were systematically investigated as a function of the model parameters. The influence of the Neel and the compensation temperature on the magnetocaloric effect is also analyzed using a microscopic model.
Understanding the inverse magnetocaloric effect in antiferro- and ferrimagnetic arrangements
Energy Technology Data Exchange (ETDEWEB)
Von Ranke, P J; De Oliveira, N A; Alho, B P; Plaza, E J R; De Sousa, V S R [Instituto de Fisica ' Armando Dias Tavares' , Universidade do Estado do Rio de Janeiro-UERJ, Rua Sao Francisco Xavier, 524, 20550-013, RJ (Brazil); Caron, L [Instituto de Fisica ' Gleb Wataghin' , Universidade Estadual de Campinas-UNICAMP, 13083-970 Campinas, SP (Brazil); Reis, M S [CICECO, Universidade de Aveiro, 3810-193 Aveiro (Portugal)], E-mail: von.ranke@uol.com.br
2009-02-04
The inverse magnetocaloric effect occurs when a magnetic material cools down under applied magnetic field in an adiabatic process. Although the existence of the inverse magnetocaloric effect was recently reported experimentally, a theoretical microscopic description is almost nonexistent. In this paper we theoretically describe the inverse magnetocaloric effect in antiferro- and ferrimagnetic systems. The inverse magnetocaloric effects were systematically investigated as a function of the model parameters. The influence of the Neel and the compensation temperature on the magnetocaloric effect is also analyzed using a microscopic model.
FAST INVERSION OF SOLAR Ca II SPECTRA
International Nuclear Information System (INIS)
Beck, C.; Choudhary, D. P.; Rezaei, R.; Louis, R. E.
2015-01-01
We present a fast (<<1 s per profile) inversion code for solar Ca II lines. The code uses an archive of spectra that are synthesized prior to the inversion under the assumption of local thermodynamic equilibrium (LTE). We show that it can be successfully applied to spectrograph data or more sparsely sampled spectra from two-dimensional spectrometers. From a comparison to a non-LTE inversion of the same set of spectra, we derive a first-order non-LTE correction to the temperature stratifications derived in the LTE approach. The correction factor is close to unity up to log τ ∼ –3 and increases to values of 2.5 and 4 at log τ = –6 in the quiet Sun and the umbra, respectively
Electrochemically driven emulsion inversion
International Nuclear Information System (INIS)
Johans, Christoffer; Kontturi, Kyoesti
2007-01-01
It is shown that emulsions stabilized by ionic surfactants can be inverted by controlling the electrical potential across the oil-water interface. The potential dependent partitioning of sodium dodecyl sulfate (SDS) was studied by cyclic voltammetry at the 1,2-dichlorobenzene|water interface. In the emulsion the potential control was achieved by using a potential-determining salt. The inversion of a 1,2-dichlorobenzene-in-water (O/W) emulsion stabilized by SDS was followed by conductometry as a function of added tetrapropylammonium chloride. A sudden drop in conductivity was observed, indicating the change of the continuous phase from water to 1,2-dichlorobenzene, i.e. a water-in-1,2-dichlorobenzene emulsion was formed. The inversion potential is well in accordance with that predicted by the hydrophilic-lipophilic deviation if the interfacial potential is appropriately accounted for
DEFF Research Database (Denmark)
Gale, A.S.; Surlyk, Finn; Anderskouv, Kresten
2013-01-01
Evidence from regional stratigraphical patterns in Santonian−Campanian chalk is used to infer the presence of a very broad channel system (5 km across) with a depth of at least 50 m, running NNW−SSE across the eastern Isle of Wight; only the western part of the channel wall and fill is exposed. W......−Campanian chalks in the eastern Isle of Wight, involving penecontemporaneous tectonic inversion of the underlying basement structure, are rejected....
Intersections, ideals, and inversion
International Nuclear Information System (INIS)
Vasco, D.W.
1998-01-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly one dimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons
Intersections, ideals, and inversion
Energy Technology Data Exchange (ETDEWEB)
Vasco, D.W.
1998-10-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.
International Nuclear Information System (INIS)
Steinhauer, L.C.; Romea, R.D.; Kimura, W.D.
1997-01-01
A new method for laser acceleration is proposed based upon the inverse process of transition radiation. The laser beam intersects an electron-beam traveling between two thin foils. The principle of this acceleration method is explored in terms of its classical and quantum bases and its inverse process. A closely related concept based on the inverse of diffraction radiation is also presented: this concept has the significant advantage that apertures are used to allow free passage of the electron beam. These concepts can produce net acceleration because they do not satisfy the conditions in which the Lawson-Woodward theorem applies (no net acceleration in an unbounded vacuum). Finally, practical aspects such as damage limits at optics are employed to find an optimized set of parameters. For reasonable assumptions an acceleration gradient of 200 MeV/m requiring a laser power of less than 1 GW is projected. An interesting approach to multi-staging the acceleration sections is also presented. copyright 1997 American Institute of Physics
Energy Technology Data Exchange (ETDEWEB)
Krapez, J.C. [Office National d' Etudes et de Recherches Aerospatiales (ONERA), Dept. Mecanique du solide et de l' Endommagement, 92 - Chatillon (France); Dubernard, A.; Stachowiak, H. [Universite d' Artois, Lab. d' Artois de Mecanique et Habitat, equipe Materiaux Thermique Instrumentation, 62 - Bethune (France)] (and others)
2000-07-01
This congress, on thermology, took place at Lyon in France, the 15-17 may 2000 with a presentation of 143 papers on the recent researches and specialized discussions. The talks published in this book are sorted out in ten thema. One of the thema concerns the experimental and inverse technics and the data processing. Seventeen talks are presented. They cover the domain of the nondestructive testing of temperature and diffusivity, many studies on the photothermal radiometry and inverse problems as the development of an inverse heat conduction method applied to the interaction flame/wall. This section presents also two papers applied to the energy conservation, one in the buildings sector with the feasibility of a method to separate thermal exchanges by convection and by radiation, the other one to measure the temperature of fuel droplets injected in a combustion chamber. (A.L.B.)
DEFF Research Database (Denmark)
Mosegaard, Klaus
2012-01-01
For non-linear inverse problems, the mathematical structure of the mapping from model parameters to data is usually unknown or partly unknown. Absence of information about the mathematical structure of this function prevents us from presenting an analytical solution, so our solution depends on our...... ability to produce efficient search algorithms. Such algorithms may be completely problem-independent (which is the case for the so-called 'meta-heuristics' or 'blind-search' algorithms), or they may be designed with the structure of the concrete problem in mind. We show that pure meta...
International Nuclear Information System (INIS)
Hicks, H.R.; Dory, R.A.; Holmes, J.A.
1983-01-01
We illustrate in some detail a 2D inverse-equilibrium solver that was constructed to analyze tokamak configurations and stellarators (the latter in the context of the average method). To ensure that the method is suitable not only to determine equilibria, but also to provide appropriately represented data for existing stability codes, it is important to be able to control the Jacobian, tilde J is identical to delta(R,Z)/delta(rho, theta). The form chosen is tilde J = J 0 (rho)R/sup l/rho where rho is a flux surface label, and l is an integer. The initial implementation is for a fixed conducting-wall boundary, but the technique can be extended to a free-boundary model
Holocaust inversion and contemporary antisemitism.
Klaff, Lesley D
2014-01-01
One of the cruellest aspects of the new antisemitism is its perverse use of the Holocaust as a stick to beat 'the Jews'. This article explains the phenomenon of 'Holocaust Inversion', which involves an 'inversion of reality' (the Israelis are cast as the 'new' Nazis and the Palestinians as the 'new' Jews) and an 'inversion of morality' (the Holocaust is presented as a moral lesson for, or even a moral indictment of, 'the Jews'). Holocaust inversion is a form of soft-core Holocaust denial, yet...
Inverse feasibility problems of the inverse maximum flow problems
Indian Academy of Sciences (India)
A linear time method to decide if any inverse maximum ﬂow (denoted General Inverse Maximum Flow problems (IMFG)) problem has solution is deduced. If IMFG does not have solution, methods to transform IMFG into a feasible problem are presented. The methods consist of modifying as little as possible the restrictions to ...
Inverse feasibility problems of the inverse maximum flow problems
Indian Academy of Sciences (India)
199–209. c Indian Academy of Sciences. Inverse feasibility problems of the inverse maximum flow problems. ADRIAN DEACONU. ∗ and ELEONOR CIUREA. Department of Mathematics and Computer Science, Faculty of Mathematics and Informatics, Transilvania University of Brasov, Brasov, Iuliu Maniu st. 50,. Romania.
Face inversion increases attractiveness.
Leder, Helmut; Goller, Juergen; Forster, Michael; Schlageter, Lena; Paul, Matthew A
2017-07-01
Assessing facial attractiveness is a ubiquitous, inherent, and hard-wired phenomenon in everyday interactions. As such, it has highly adapted to the default way that faces are typically processed: viewing faces in upright orientation. By inverting faces, we can disrupt this default mode, and study how facial attractiveness is assessed. Faces, rotated at 90 (tilting to either side) and 180°, were rated on attractiveness and distinctiveness scales. For both orientations, we found that faces were rated more attractive and less distinctive than upright faces. Importantly, these effects were more pronounced for faces rated low in upright orientation, and smaller for highly attractive faces. In other words, the less attractive a face was, the more it gained in attractiveness by inversion or rotation. Based on these findings, we argue that facial attractiveness assessments might not rely on the presence of attractive facial characteristics, but on the absence of distinctive, unattractive characteristics. These unattractive characteristics are potentially weighed against an individual, attractive prototype in assessing facial attractiveness. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.
Zhang, Dongliang
2013-01-01
To increase the illumination of the subsurface and to eliminate the dependency of FWI on the source wavelet, we propose multiples waveform inversion (MWI) that transforms each hydrophone into a virtual point source with a time history equal to that of the recorded data. These virtual sources are used to numerically generate downgoing wavefields that are correlated with the backprojected surface-related multiples to give the migration image. Since the recorded data are treated as the virtual sources, knowledge of the source wavelet is not required, and the subsurface illumination is greatly enhanced because the entire free surface acts as an extended source compared to the radiation pattern of a traditional point source. Numerical tests on the Marmousi2 model show that the convergence rate and the spatial resolution of MWI is, respectively, faster and more accurate then FWI. The potential pitfall with this method is that the multiples undergo more than one roundtrip to the surface, which increases attenuation and reduces spatial resolution. This can lead to less resolved tomograms compared to conventional FWI. The possible solution is to combine both FWI and MWI in inverting for the subsurface velocity distribution.
Coin tossing and Laplace inversion
Indian Academy of Sciences (India)
MS received 5 May 1999; revised 3 April 2000. Abstract. An analysis of exchangeable sequences of coin tossings leads to inversion formulae for Laplace transforms of probability measures. Keywords. Laplace inversion; moment problem; exchangeable probabilities. 1. Introduction. There is an intimate relationship between ...
Inverse problems for Maxwell's equations
Romanov, V G
1994-01-01
The Inverse and Ill-Posed Problems Series is a series of monographs publishing postgraduate level information on inverse and ill-posed problems for an international readership of professional scientists and researchers. The series aims to publish works which involve both theory and applications in, e.g., physics, medicine, geophysics, acoustics, electrodynamics, tomography, and ecology.
Algebraic properties of generalized inverses
Cvetković‐Ilić, Dragana S
2017-01-01
This book addresses selected topics in the theory of generalized inverses. Following a discussion of the “reverse order law” problem and certain problems involving completions of operator matrices, it subsequently presents a specific approach to solving the problem of the reverse order law for {1} -generalized inverses. Particular emphasis is placed on the existence of Drazin invertible completions of an upper triangular operator matrix; on the invertibility and different types of generalized invertibility of a linear combination of operators on Hilbert spaces and Banach algebra elements; on the problem of finding representations of the Drazin inverse of a 2x2 block matrix; and on selected additive results and algebraic properties for the Drazin inverse. In addition to the clarity of its content, the book discusses the relevant open problems for each topic discussed. Comments on the latest references on generalized inverses are also included. Accordingly, the book will be useful for graduate students, Ph...
Directory of Open Access Journals (Sweden)
Calvez V.
2010-12-01
Full Text Available We consider the radiative transfer equation (RTE with reflection in a three-dimensional domain, infinite in two dimensions, and prove an existence result. Then, we study the inverse problem of retrieving the optical parameters from boundary measurements, with help of existing results by Choulli and Stefanov. This theoretical analysis is the framework of an attempt to model the color of the skin. For this purpose, a code has been developed to solve the RTE and to study the sensitivity of the measurements made by biophysicists with respect to the physiological parameters responsible for the optical properties of this complex, multi-layered material. On étudie l’équation du transfert radiatif (ETR dans un domaine tridimensionnel infini dans deux directions, et on prouve un résultat d’existence. On s’intéresse ensuite à la reconstruction des paramètres optiques à partir de mesures faites au bord, en s’appuyant sur des résultats de Choulli et Stefanov. Cette analyse sert de cadre théorique à un travail de modélisation de la couleur de la peau. Dans cette perspective, un code à été développé pour résoudre l’ETR et étudier la sensibilité des mesures effectuées par les biophysiciens par rapport aux paramètres physiologiques tenus pour responsables des propriétés optiques de ce complexe matériau multicouche.
Silicon MIS/inversion-layer solar cells
Olsen, L. C.
1982-10-01
Silicon Metal-Insulator-Semiconductor/Inversion-Layer (MIS-IL) solar cells were investigated as an approach to low cost terrestrial photovoltaics. Considerable progress was made concerning the development of procedures for SiO deposition for inversion-layer formation, the characterization of the fixed charge in deposited SiO layers, surface state density at the Si-SiO interface, fabrication and characterization of MIS-IL solar cells. Improvements were also made in the theory of MIS-IL solar cells, and utilized to calculate cell performance for a range of insulator charge and base resistivities. Inversion layer formation was studied in several ways. MOS devices was analyzed to determine the magnitude of the net positive charge, Q/sub POS/, vensus surface potential, Psi/sub S/. In situ sheet resistance measurements was made to determine the charge distribution within the deposited SiO layer. Finally, estimates of Q/sub POS/ obtained by comparing experimental results for MIS-IL cells and theory are compared with values of Q/sub POS/ determined for MOS structures fabricated simultaneously with the solar cells. Cell fabrication procedures emphasized low temperature processing.
Bayesian Approach to Inverse Problems
2008-01-01
Many scientific, medical or engineering problems raise the issue of recovering some physical quantities from indirect measurements; for instance, detecting or quantifying flaws or cracks within a material from acoustic or electromagnetic measurements at its surface is an essential problem of non-destructive evaluation. The concept of inverse problems precisely originates from the idea of inverting the laws of physics to recover a quantity of interest from measurable data.Unfortunately, most inverse problems are ill-posed, which means that precise and stable solutions are not easy to devise. Regularization is the key concept to solve inverse problems.The goal of this book is to deal with inverse problems and regularized solutions using the Bayesian statistical tools, with a particular view to signal and image estimation
Testing earthquake source inversion methodologies
Page, Morgan T.
2011-01-01
Source Inversion Validation Workshop; Palm Springs, California, 11-12 September 2010; Nowadays earthquake source inversions are routinely performed after large earthquakes and represent a key connection between recorded seismic and geodetic data and the complex rupture process at depth. The resulting earthquake source models quantify the spatiotemporal evolution of ruptures. They are also used to provide a rapid assessment of the severity of an earthquake and to estimate losses. However, because of uncertainties in the data, assumed fault geometry and velocity structure, and chosen rupture parameterization, it is not clear which features of these source models are robust. Improved understanding of the uncertainty and reliability of earthquake source inversions will allow the scientific community to use the robust features of kinematic inversions to more thoroughly investigate the complexity of the rupture process and to better constrain other earthquakerelated computations, such as ground motion simulations and static stress change calculations.
Parameter estimation and inverse problems
Aster, Richard C; Thurber, Clifford H
2005-01-01
Parameter Estimation and Inverse Problems primarily serves as a textbook for advanced undergraduate and introductory graduate courses. Class notes have been developed and reside on the World Wide Web for faciliting use and feedback by teaching colleagues. The authors'' treatment promotes an understanding of fundamental and practical issus associated with parameter fitting and inverse problems including basic theory of inverse problems, statistical issues, computational issues, and an understanding of how to analyze the success and limitations of solutions to these probles. The text is also a practical resource for general students and professional researchers, where techniques and concepts can be readily picked up on a chapter-by-chapter basis.Parameter Estimation and Inverse Problems is structured around a course at New Mexico Tech and is designed to be accessible to typical graduate students in the physical sciences who may not have an extensive mathematical background. It is accompanied by a Web site that...
Statistical perspectives on inverse problems
DEFF Research Database (Denmark)
Andersen, Kim Emil
of the interior of an object from electrical boundary measurements. One part of this thesis concerns statistical approaches for solving, possibly non-linear, inverse problems. Thus inverse problems are recasted in a form suitable for statistical inference. In particular, a Bayesian approach for regularisation...... problem is given in terms of probability distributions. Posterior inference is obtained by Markov chain Monte Carlo methods and new, powerful simulation techniques based on e.g. coupled Markov chains and simulated tempering is developed to improve the computational efficiency of the overall simulation......Inverse problems arise in many scientific disciplines and pertain to situations where inference is to be made about a particular phenomenon from indirect measurements. A typical example, arising in diffusion tomography, is the inverse boundary value problem for non-invasive reconstruction...
Computation of inverse magnetic cascades
International Nuclear Information System (INIS)
Montgomery, D.
1981-10-01
Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed
Thermal measurements and inverse techniques
Orlande, Helcio RB; Maillet, Denis; Cotta, Renato M
2011-01-01
With its uncommon presentation of instructional material regarding mathematical modeling, measurements, and solution of inverse problems, Thermal Measurements and Inverse Techniques is a one-stop reference for those dealing with various aspects of heat transfer. Progress in mathematical modeling of complex industrial and environmental systems has enabled numerical simulations of most physical phenomena. In addition, recent advances in thermal instrumentation and heat transfer modeling have improved experimental procedures and indirect measurements for heat transfer research of both natural phe
Coin tossing and Laplace inversion
Indian Academy of Sciences (India)
of a probability measure " on Е0Y 1К via the obvious change of variables e└t И xX An inversion formula for " in terms of its moments yields an inversion formula for # in terms of the values of its Laplace transform at n И 0Y 1Y 2Y ... and vice versa. In our discussion we allow " (respectively #) to have positive mass at 0 ...
EDITORIAL: Inverse Problems in Engineering
West, Robert M.; Lesnic, Daniel
2007-01-01
Presented here are 11 noteworthy papers selected from the Fifth International Conference on Inverse Problems in Engineering: Theory and Practice held in Cambridge, UK during 11-15 July 2005. The papers have been peer-reviewed to the usual high standards of this journal and the contributions of reviewers are much appreciated. The conference featured a good balance of the fundamental mathematical concepts of inverse problems with a diverse range of important and interesting applications, which are represented here by the selected papers. Aspects of finite-element modelling and the performance of inverse algorithms are investigated by Autrique et al and Leduc et al. Statistical aspects are considered by Emery et al and Watzenig et al with regard to Bayesian parameter estimation and inversion using particle filters. Electrostatic applications are demonstrated by van Berkel and Lionheart and also Nakatani et al. Contributions to the applications of electrical techniques and specifically electrical tomographies are provided by Wakatsuki and Kagawa, Kim et al and Kortschak et al. Aspects of inversion in optical tomography are investigated by Wright et al and Douiri et al. The authors are representative of the worldwide interest in inverse problems relating to engineering applications and their efforts in producing these excellent papers will be appreciated by many readers of this journal.
A thermally tunable inverse opal photonic crystal for monitoring glass transition.
Sun, Liguo; Xie, Zhuoying; Xu, Hua; Xu, Ming; Han, Guozhi; Wang, Cheng; Bai, Xuduo; Gu, ZhongZe
2012-03-01
An optical method was developed to monitor the glass transition of the polymer by taking advantage of reflection spectrum change of the thermally tunable inverse opal photonic crystal. The thermally tunable photonic bands of the polymer inverse opal photonic crystal were traceable to the segmental motion of macromolecules, and the segmental motion was temperature dependent. By observing the reflection spectrum change of the polystyrene inverse opal photonic crystal during thermal treatment, the glass transition temperature of polystyrene was gotten. Both changes of the position and intensity of the reflection peak were observed during the glass transition process of the polystyrene inverse opal photonic crystal. The optical change of inverse opal photonic crystal was so large that the glass transition temperature could even be estimated by naked eyes. The glass transition temperature derived from this method was consistent with the values measured by differential scanning calorimeter.
Chromatid Painting for Chromosomal Inversion Detection Project
National Aeronautics and Space Administration — We propose a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and inversions) have profound genetic...
An Inverse Thellier Method of Paleointensity Determination
Dunlop, D. J.; Yu, Y.
2002-12-01
Inverse thermoremanent magnetization (ITRM) is produced when magnetite warms from below the Verwey transition at 120 K to room temperature in a magnetic field H. ITRM could be acquired by magnetite-bearing meteorites if their interiors remain below 120 K at the time of impact and they subsequently warm in the Earth's field. ITRM might possibly be distinguished from genuine extraterrestrial remanence by the recorded field intensity H, since the present field is well mapped over the Earth. To test this idea, we have invented an "inverse Thellier" paleointensity method using double cooling-warming steps below 300 K in place of double heating-cooling steps above 300 K. We used as the "NRM" a total ITRM produced by warming natural samples and sized synthetic magnetites from 30 K to 300 K. The field H was either 0.1 or 0.2 mT (in some experiments, total ITRM was produced in one of these fields and partial ITRMs in the other). The first cooling-warming step, usually to 200 K, was in zero field. Remanence measured after this step gives the loss in NRM. The second cooling-warming step was in field H. The difference in remanence between the second and first steps gives the partial ITRM gained. NRM losses and partial ITRM gains in further steps to 150, 130, 120, 110, 100 and 90 K, generate an "inverse Arai plot", whose slope is the ratio between the ITRM and partial ITRM fields. We tested magnetites with sizes of 0.065, 0.2, 0.6, 1.0, 1.1, 3, 6, 9, 17 and 135 micrometers, both unannealed and annealed, and two samples of the Tudor Gabbro containing elongated single-domain magnetite. The results are discouraging. Despite a variety of shapes of cooling-warming cycles, most inverse Arai plots have the convex-down form typical of Arai plots for TRM in multidomain grains. More ITRM is lost in early zero-field steps than is regained as partial ITRM in in-field steps, even for grains that are single-domain or nearly so. The only quasi-linear plots were for the two gabbros, which also
Inverse calculation of power density for laser surface treatment
Römer, Gerardus Richardus, Bernardus, Engelina; Meijer, J.
2000-01-01
Laser beam surface treatment requires a well-defined temperature profile. In this paper an analytic method is presented to solve the inverse problem of heat conduction in solids, based on the 2-dimensional Fourier transform. As a result, the required power density profile of the laser beam can be
Inverse comptonization vs. thermal synchrotron
International Nuclear Information System (INIS)
Fenimore, E.E.; Klebesadel, R.W.; Laros, J.G.
1983-01-01
There are currently two radiation mechanisms being considered for gamma-ray bursts: thermal synchrotron and inverse comptonization. They are mutually exclusive since thermal synchrotron requires a magnetic field of approx. 10 12 Gauss whereas inverse comptonization cannot produce a monotonic spectrum if the field is larger than 10 11 and is too inefficient relative to thermal synchrotron unless the field is less than 10 9 Gauss. Neither mechanism can explain completely the observed characteristics of gamma-ray bursts. However, we conclude that thermal synchrotron is more consistent with the observations if the sources are approx. 40 kpc away whereas inverse comptonization is more consistent if they are approx. 300 pc away. Unfortunately, the source distance is still not known and, thus, the radiation mechanism is still uncertain
Inverse comorbidity in multiple sclerosis
DEFF Research Database (Denmark)
Thormann, Anja; Koch-Henriksen, Nils; Laursen, Bjarne
2016-01-01
discovery rate and investigated each of eight pre-specified comorbidity categories: psychiatric, cerebrovascular, cardiovascular, lung, and autoimmune comorbidities, diabetes, cancer, and Parkinson's disease. Results A total of 8947 MS-cases and 44,735 controls were eligible for inclusion. We found...... This study showed a decreased risk of cancers and pulmonary diseases after onset of MS. Identification of inverse comorbidity and of its underlying mechanisms may provide important new entry points into the understanding of MS.......Background Inverse comorbidity is disease occurring at lower rates than expected among persons with a given index disease. The objective was to identify inverse comorbidity in MS. Methods We performed a combined case-control and cohort study in a total nationwide cohort of cases with clinical onset...
Inverse photoemission of uranium oxides
International Nuclear Information System (INIS)
Roussel, P.; Morrall, P.; Tull, S.J.
2009-01-01
Understanding the itinerant-localised bonding role of the 5f electrons in the light actinides will afford an insight into their unusual physical and chemical properties. In recent years, the combination of core and valance band electron spectroscopies with theoretic modelling have already made significant progress in this area. However, information of the unoccupied density of states is still scarce. When compared to the forward photoemission techniques, measurements of the unoccupied states suffer from significantly less sensitivity and lower resolution. In this paper, we report on our experimental apparatus, which is designed to measure the inverse photoemission spectra of the light actinides. Inverse photoemission spectra of UO 2 and UO 2.2 along with the corresponding core and valance electron spectra are presented in this paper. UO 2 has been reported previously, although through its inclusion here it allows us to compare and contrast results from our experimental apparatus to the previous Bremsstrahlung Isochromat Spectroscopy and Inverse Photoemission Spectroscopy investigations
Inverse source problems in elastodynamics
Bao, Gang; Hu, Guanghui; Kian, Yavar; Yin, Tao
2018-04-01
We are concerned with time-dependent inverse source problems in elastodynamics. The source term is supposed to be the product of a spatial function and a temporal function with compact support. We present frequency-domain and time-domain approaches to show uniqueness in determining the spatial function from wave fields on a large sphere over a finite time interval. The stability estimate of the temporal function from the data of one receiver and the uniqueness result using partial boundary data are proved. Our arguments rely heavily on the use of the Fourier transform, which motivates inversion schemes that can be easily implemented. A Landweber iterative algorithm for recovering the spatial function and a non-iterative inversion scheme based on the uniqueness proof for recovering the temporal function are proposed. Numerical examples are demonstrated in both two and three dimensions.
Optimization for nonlinear inverse problem
International Nuclear Information System (INIS)
Boyadzhiev, G.; Brandmayr, E.; Pinat, T.; Panza, G.F.
2007-06-01
The nonlinear inversion of geophysical data in general does not yield a unique solution, but a single model, representing the investigated field, is preferred for an easy geological interpretation of the observations. The analyzed region is constituted by a number of sub-regions where the multi-valued nonlinear inversion is applied, which leads to a multi-valued solution. Therefore, combining the values of the solution in each sub-region, many acceptable models are obtained for the entire region and this complicates the geological interpretation of geophysical investigations. In this paper are presented new methodologies, capable to select one model, among all acceptable ones, that satisfies different criteria of smoothness in the explored space of solutions. In this work we focus on the non-linear inversion of surface waves dispersion curves, which gives structural models of shear-wave velocity versus depth, but the basic concepts have a general validity. (author)
Inverse transient thermoelastic deformations in thin circular plates
Indian Academy of Sciences (India)
g(r, t). On applying the finite Hankel transform and Laplace transform to (1) to (6) and then obtaining the inverses of the resultant equations, we obtain the expressions for temperature distribution and unknown heating temperature respectively, as. T(r, z, t) = ∞. ∑ n=1. ∞. ∑ m=1. Amn(ξn, λm) · φm(n, t) · J0(ξnr). ×. [. −λm cos.
The universal behavior of inverse magnetocaloric effect in antiferromagnetic materials
Biswas, Anis; Chandra, Sayan; Samanta, Tapas; Phan, M. H.; Das, I.; Srikanth, H.
2013-05-01
We report the universal behavior of inverse magnetocaloric effect (IMCE) in antiferromagnetic materials. In contrast to the universal behavior of conventional magnetocaloric effect often observed in ferromagnetic systems, a phenomenological universal master curve can be constructed to describe the temperature dependence of magnetic entropy change for IMCE without rescaling the temperature axis. The proposed universal curve method allows extrapolating the magnetic entropy change of an IMCE material, which would be imperative to judge its suitability in actual magnetic refrigeration devices.
Inverse methods in hydrologic optics
Directory of Open Access Journals (Sweden)
Howard R. Gordon
2002-03-01
Full Text Available Methods for solving the hydrologic-optics inverse problem, i.e., estimating the inherent optical properties of a water body based solely on measurements of the apparent optical properties, are reviewed in detail. A new method is developed for the inverse problem in water bodies in which fluorescence is important. It is shown that in principle, given profiles of the spectra of up- and downwelling irradiance, estimation of the coefficient of inelastic scattering from any wave band to any other wave band can be effected.
Inverse Interval Matrix: A Survey
Czech Academy of Sciences Publication Activity Database
Rohn, Jiří; Farhadsefat, R.
2011-01-01
Roč. 22, - (2011), s. 704-719 E-ISSN 1081-3810 R&D Projects: GA ČR GA201/09/1957; GA ČR GC201/08/J020 Institutional research plan: CEZ:AV0Z10300504 Keywords : interval matrix * inverse interval matrix * NP-hardness * enclosure * unit midpoint * inverse sign stability * nonnegative invertibility * absolute value equation * algorithm Subject RIV: BA - General Mathematics Impact factor: 0.808, year: 2010 http://www.math.technion.ac.il/iic/ela/ela-articles/articles/vol22_pp704-719.pdf
Size Estimates in Inverse Problems
Di Cristo, Michele
2014-01-06
Detection of inclusions or obstacles inside a body by boundary measurements is an inverse problems very useful in practical applications. When only finite numbers of measurements are available, we try to detect some information on the embedded object such as its size. In this talk we review some recent results on several inverse problems. The idea is to provide constructive upper and lower estimates of the area/volume of the unknown defect in terms of a quantity related to the work that can be expressed with the available boundary data.
-Dimensional Fractional Lagrange's Inversion Theorem
Directory of Open Access Journals (Sweden)
F. A. Abd El-Salam
2013-01-01
Full Text Available Using Riemann-Liouville fractional differential operator, a fractional extension of the Lagrange inversion theorem and related formulas are developed. The required basic definitions, lemmas, and theorems in the fractional calculus are presented. A fractional form of Lagrange's expansion for one implicitly defined independent variable is obtained. Then, a fractional version of Lagrange's expansion in more than one unknown function is generalized. For extending the treatment in higher dimensions, some relevant vectors and tensors definitions and notations are presented. A fractional Taylor expansion of a function of -dimensional polyadics is derived. A fractional -dimensional Lagrange inversion theorem is proved.
Statistical and Computational Inverse Problems
Kaipio, Jari
2005-01-01
Develops the statistical approach to inverse problems with an emphasis on modeling and computations. The book discusses the measurement noise modeling and Bayesian estimation, and uses Markov Chain Monte Carlo methods to explore the probability distributions. It is for researchers and advanced students in applied mathematics.
Coin Tossing and Laplace Inversion
Indian Academy of Sciences (India)
An analysis of exchangeable sequences of coin tossings leads to inversion formulae for Laplace transforms of probability measures. Author Affiliations. J C Gupta1 2. Indian Statistical Institute, New Delhi 110 016, India; 32, Mirdha Tola, Budaun 243 601, India. Dates. Manuscript received: 5 May 1999; Manuscript revised: 3 ...
Givental Graphs and Inversion Symmetry
Dunin-Barkovskiy, P.; Shadrin, S.; Spitz, L.
2013-01-01
Inversion symmetry is a very non-trivial discrete symmetry of Frobenius manifolds. It was obtained by Dubrovin from one of the elementary Schlesinger transformations of a special ODE associated to a Frobenius manifold. In this paper, we review the Givental group action on Frobenius manifolds in
Wave-equation dispersion inversion
Li, Jing
2016-12-08
We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.
Adjoint modeling for acoustic inversion
Hursky, Paul; Porter, Michael B.; Cornuelle, B. D.; Hodgkiss, W. S.; Kuperman, W. A.
2004-02-01
The use of adjoint modeling for acoustic inversion is investigated. An adjoint model is derived from a linearized forward propagation model to propagate data-model misfit at the observation points back through the medium to the medium perturbations not being accounted for in the model. This adjoint model can be used to aid in inverting for these unaccounted medium perturbations. Adjoint methods are being applied to a variety of inversion problems, but have not drawn much attention from the underwater acoustic community. This paper presents an application of adjoint methods to acoustic inversion. Inversions are demonstrated in simulation for both range-independent and range-dependent sound speed profiles using the adjoint of a parabolic equation model. Sensitivity and error analyses are discussed showing how the adjoint model enables calculations to be performed in the space of observations, rather than the often much larger space of model parameters. Using an adjoint model enables directions of steepest descent in the model parameters (what we invert for) to be calculated using far fewer modeling runs than if a forward model only were used.
Workflows for Full Waveform Inversions
Boehm, Christian; Krischer, Lion; Afanasiev, Michael; van Driel, Martin; May, Dave A.; Rietmann, Max; Fichtner, Andreas
2017-04-01
Despite many theoretical advances and the increasing availability of high-performance computing clusters, full seismic waveform inversions still face considerable challenges regarding data and workflow management. While the community has access to solvers which can harness modern heterogeneous computing architectures, the computational bottleneck has fallen to these often manpower-bounded issues that need to be overcome to facilitate further progress. Modern inversions involve huge amounts of data and require a tight integration between numerical PDE solvers, data acquisition and processing systems, nonlinear optimization libraries, and job orchestration frameworks. To this end we created a set of libraries and applications revolving around Salvus (http://salvus.io), a novel software package designed to solve large-scale full waveform inverse problems. This presentation focuses on solving passive source seismic full waveform inversions from local to global scales with Salvus. We discuss (i) design choices for the aforementioned components required for full waveform modeling and inversion, (ii) their implementation in the Salvus framework, and (iii) how it is all tied together by a usable workflow system. We combine state-of-the-art algorithms ranging from high-order finite-element solutions of the wave equation to quasi-Newton optimization algorithms using trust-region methods that can handle inexact derivatives. All is steered by an automated interactive graph-based workflow framework capable of orchestrating all necessary pieces. This naturally facilitates the creation of new Earth models and hopefully sparks new scientific insights. Additionally, and even more importantly, it enhances reproducibility and reliability of the final results.
Vortex annihilation and inverse cascades in two dimensional superfluid turbulence
Lucas, Andrew; Chesler, Paul M.
2015-03-01
The dynamics of a dilute mixture of vortices and antivortices in a turbulent two-dimensional superfluid at finite temperature is well described by first order Hall-Vinen-Iordanskii equations, or dissipative point vortex dynamics. These equations are governed by a single dimensionless parameter: the ratio of the strength of drag forces to Magnus forces on vortices. When this parameter is small, we demonstrate using numerical simulations that the resulting superfluid enjoys an inverse energy cascade where small scale stirring leads to large scale vortex clustering. We argue analytically and numerically that the vortex annihilation rate in a laminar flow may be parametrically smaller than the rate in a turbulent flow with an inverse cascade. This suggests a new way to detect inverse cascades in experiments on two-dimensional superfluid turbulence using cold atomic gases, where traditional probes of turbulence such as the energy spectrum are not currently accessible.
Hedland, D. A.; Degonia, P. K.
1974-01-01
The RAE-1 spacecraft inversion performed October 31, 1972 is described based upon the in-orbit dynamical data in conjunction with results obtained from previously developed computer simulation models. The computer simulations used are predictive of the satellite dynamics, including boom flexing, and are applicable during boom deployment and retraction, inter-phase coast periods, and post-deployment operations. Attitude data, as well as boom tip data, were analyzed in order to obtain a detailed description of the dynamical behavior of the spacecraft during and after the inversion. Runs were made using the computer model and the results were analyzed and compared with the real time data. Close agreement between the actual recorded spacecraft attitude and the computer simulation results was obtained.
Validation of OSIRIS Ozone Inversions
Gudnason, P.; Evans, W. F.; von Savigny, C.; Sioris, C.; Halley, C.; Degenstein, D.; Llewellyn, E. J.; Petelina, S.; Gattinger, R. L.; Odin Team
2002-12-01
The OSIRIS instrument onboard the Odin satellite, that was launched on February 20, 2001, is a combined optical spectrograph and infrared imager that obtains profil sets of atmospheric spectra from 280 to 800 nm when Odin scans the terrestrial limb. It has been possible to make a preliminary analysis of the ozone profiles using the Chappuis absorption feature. Three algorithms have been developed for ozone profile inversions from these limb spectra sets. We have dubbed these the Gattinger, Von Savigny-Flittner and DOAS methods. These are being evaluated against POAM and other satellite data. Based on performance, one of these will be selected for the operational algorithm. The infrared imager data have been used by Degenstein with the tomographic inversion procedure to derive ozone concentrations above 60 km. This paper will present some of these initial observations and indicate the best algorithm potential of OSIRIS to make spectacular advances in the study of terrestrial ozone.
Inverse problem in transformation optics
Novitsky, Andrey V.
2011-01-01
The straightforward method of transformation optics implies that one starts from the coordinate transformation and determines the Jacobian matrix, the fields and material parameters of the cloak. However, the coordinate transformation appears as an optional function: it is not necessary to know it. We offer the solution of some sort of inverse problem: starting from the fields in the invisibility cloak we directly derive the permittivity and permeability tensors of the cloaking shell. This ap...
Fourier reconstruction with sparse inversions
Zwartjes, P.M.
2005-01-01
In seismic exploration an image of the subsurface is generated from seismic data through various data processing algorithms. When the data is not acquired on an equidistantly spaced grid, artifacts may result in the final image. Fourier reconstruction is an interpolation technique that can reduce these artifacts by generating uniformly sampled data from such non-uniformly sampled data. The method works by estimating via least-squares inversion the Fourier coefficients that describe the non-un...
The Inverse of Banded Matrices
2013-01-01
for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite ...numbers of summed or subtracted terms in computing the inverse of a term of an upper (lower) triangular matrix are the generalized order-k Fibonacci ... Fibonacci numbers are the usual Fibonacci numbers, that is, f 2m = Fm (mth Fibonacci number). When also k = 3, c1 = c2 = c3 = 1, then the generalized order-3
Improved Inversion of Needle Probe Data for the Determination of Rock Thermal Properties
DEFF Research Database (Denmark)
Bording, Thue Sylvester; Balling, N.; Nielsen, S.B.
Heat flow, thermal conductivity and thermal diffusivity are essential properties in subsurface temperature modelling. We present initial results of a novel inversion approach for laboratory measurements of rock thermal conductivity and thermal diffusivity by the needle probe method. Instead...... of analytical expressions, we use a numerical finite element procedure for the forward temperature response. A Markov Chain Monte Carlo Metropolis Hastings inversion procedure produces estimates of rock thermal parameters with uncertainties. .....
Inverse-magnetron mass spectrometer
International Nuclear Information System (INIS)
Pakulin, V.N.
1979-01-01
Considered is the operation of a typical magnetron mass spectrometer with an internal ion source and that of an inverse magnetron mass spectrometer with an external ion source. It is found that for discrimination of the same mass using the inverse design of mass spectrometers it is possible to employ either r 2 /r 1 times lesser magnetic fields at equal accelerating source-collector voltages, or r 2 /r 1 higher accelerating voltages at equal magnetic fields, as compared to the typical design (r 1 and r 2 being radii of the internal and external electrodes of the analyser, respectively). The design of an inverse-magnetron mass spectrometer is described. The mass analyzer is formed by a cylindrical electrode of 3 mm diameter and a coaxial tubular cylinder of 55 mm diameter. External to the analyzer is an ionizing chamber at the pressure of up to 5x10 -6 torr. The magnetic field along the chamber axis produced by a solenoid was 300 Oe. At the accelerating voltage of 100 V and mass 28, the spectrometer has a resolution of 30 at a half-peak height
Inverse problems for difference equations with quadratic ...
African Journals Online (AJOL)
Inverse problems for difference equations with quadratic Eigenparameter dependent boundary conditions. Sonja Currie, Anne D. Love. Abstract. This paper inductively investigates an inverse problem for difference boundary value problems with boundary conditions that depend quadratically on the eigenparameter.
Fast computation of the inverse CMH model
Patel, Umesh D.; Della Torre, Edward
2001-12-01
A fast computational method based on differential equation approach for inverse Della Torre, Oti, Kádár (DOK) model has been extended for the inverse Complete Moving Hysteresis (CMH) model. A cobweb technique for calculating the inverse CMH model is also presented. The two techniques differ from the point of view of flexibility, accuracy, and computation time. Simulation results of the inverse computation for both methods are presented.
LA INVERSION INMOBILIARIA INDIRECTA EN ESPANA.
Joan MONTLLOR-SERRATS; Anna M. PANOSA-GUBAU
2013-01-01
En este articulo se revisan los instrumentos de inversion indirecta inmobiliaria en Espana, desde la creacion en 1992 de los Fondos y Sociedades de Inversion inmobiliaria (FII y SII) hasta la creacion de la primera Sociedad de inversion del mercado inmobiliario (SOCIMI) en 2013. Se analizan las caracteristicas de los mismos y asimismo los motivos por los cuales estas figuras de inversion no han tenido mucha demanda hasta el momento, en comparacion con los REITs (Real Estate Investment Trusts)...
Codimension zero laminations are inverse limits
Lozano Rojo, Álvaro
2013-01-01
The aim of the paper is to investigate the relation between inverse limit of branched manifolds and codimension zero laminations. We give necessary and sufficient conditions for such an inverse limit to be a lamination. We also show that codimension zero laminations are inverse limits of branched manifolds. The inverse limit structure allows us to show that equicontinuous codimension zero laminations preserves a distance function on transversals.
Inversion: A Most Useful Kind of Transformation.
Dubrovsky, Vladimir
1992-01-01
The transformation assigning to every point its inverse with respect to a circle with given radius and center is called an inversion. Discusses inversion with respect to points, circles, angles, distances, space, and the parallel postulate. Exercises related to these topics are included. (MDH)
Surface layer temperature inversion in the Bay of Bengal
Digital Repository Service at National Institute of Oceanography (India)
Pankajakshan, T.; Gopalakrishna, V.V.; Muraleedharan, P.M.; Reddy, G.V.; Araligidad, N.; Shenoy, Shrikant
evaporation rates. However, the precipitation in the Bay changes signiﬁcantly betweensummerandwinter(Varkeyetal., 1996). ThephysiographicconditionsofsouthernAsiaare *Correspondingauthor.Fax:+91-832-223340. E-mail address: pankaj@csnio.ren.nic.in, pankaj..., the excessive precipitation (P) over evaporation (E) during summer is another signiﬁcant source of fresh water to the Bay (Harenduprakash and Mitra, 1988; Prasad, 1997). Thus, the large river runoff and excess precipitation over evaporation during summer monsoon...
Inverse estimation for the unknown frost geometry on the external wall of a forced-convection pipe
Energy Technology Data Exchange (ETDEWEB)
Chen, Wen-Lih; Yang, Yu-Ching [Clean Energy Center, Department of Mechanical Engineering, Kun Shan University, Yung-Kang City, Tainan 710-03 (China)
2009-06-15
In this study, a conjugate gradient method based inverse algorithm is applied to estimate the unknown frost-layer boundary profile on the external wall of a pipe system using temperature measurements. It is assumed that no prior information is available on the functional form of the unknown profile; hence the procedure is classified as the function estimation in inverse calculation. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The accuracy of the inverse analysis is examined by using simulated exact and inexact temperature measurements. Results show that an excellent estimation on boundary profile can be obtained for the test case considered in this study. (author)
Inverse problem in transformation optics
DEFF Research Database (Denmark)
Novitsky, Andrey
2011-01-01
. We offer the solution of some sort of inverse problem: starting from the fields in the invisibility cloak we directly derive the permittivity and permeability tensors of the cloaking shell. This approach can be useful for finding material parameters for the specified electromagnetic fields......The straightforward method of transformation optics implies that one starts from the coordinate transformation and determines the Jacobian matrix, the fields and material parameters of the cloak. However, the coordinate transformation appears as an optional function: it is not necessary to know it...... in the cloaking shell without knowing the coordinate transformation....
Iterative optimization in inverse problems
Byrne, Charles L
2014-01-01
Iterative Optimization in Inverse Problems brings together a number of important iterative algorithms for medical imaging, optimization, and statistical estimation. It incorporates recent work that has not appeared in other books and draws on the author's considerable research in the field, including his recently developed class of SUMMA algorithms. Related to sequential unconstrained minimization methods, the SUMMA class includes a wide range of iterative algorithms well known to researchers in various areas, such as statistics and image processing. Organizing the topics from general to more
Mathematical and numerical modeling of inverse heat conduction problem
Directory of Open Access Journals (Sweden)
Sterian DANAILA
2014-12-01
Full Text Available The present paper refers to the assessment of three numerical methods for solving the inverse heat conduction problem: the Alifanov’s iterative regularization method, the Tikhonov local regularization method and the Tikhonov equation regularization method, respectively. For all methods we developed numerical algorithms for reconstruction of the unsteady boundary condition imposing some restrictions for the unsteady temperature field in the interior points. Numerical tests allow evaluating the accuracy of the considered methods.
Understanding the inverse magnetocaloric effect through a simple theoretical model
Energy Technology Data Exchange (ETDEWEB)
Ranke, P.J. von, E-mail: von.ranke@uol.com.b [Instituto de Fisica Armando Dias Tavares-Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier, 524, Rio de Janeiro 20550-013 (Brazil); Alho, B.P.; Nobrega, E.P.; Oliveira, N.A. de [Instituto de Fisica Armando Dias Tavares-Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier, 524, Rio de Janeiro 20550-013 (Brazil)
2009-10-15
We investigated the inverse magnetocaloric effect using a theoretical magnetic model formed by two coupled magnetic lattices to describe a ferrimagnetic system. The influence of the compensation temperature, and the ferrimagnetic-paramagnetic phase transition on the magnetocaloric effect was analyzed. Also, a relation between the area under the magnetocaloric curve and the net magnetic moment of a ferrimagnetic system was established in this work.
Inverse design of multicomponent assemblies
Piñeros, William D.; Lindquist, Beth A.; Jadrich, Ryan B.; Truskett, Thomas M.
2018-03-01
Inverse design can be a useful strategy for discovering interactions that drive particles to spontaneously self-assemble into a desired structure. Here, we extend an inverse design methodology—relative entropy optimization—to determine isotropic interactions that promote assembly of targeted multicomponent phases, and we apply this extension to design interactions for a variety of binary crystals ranging from compact triangular and square architectures to highly open structures with dodecagonal and octadecagonal motifs. We compare the resulting optimized (self- and cross) interactions for the binary assemblies to those obtained from optimization of analogous single-component systems. This comparison reveals that self-interactions act as a "primer" to position particles at approximately correct coordination shell distances, while cross interactions act as the "binder" that refines and locks the system into the desired configuration. For simpler binary targets, it is possible to successfully design self-assembling systems while restricting one of these interaction types to be a hard-core-like potential. However, optimization of both self- and cross interaction types appears necessary to design for assembly of more complex or open structures.
LHC Report: 2 inverse femtobarns!
Mike Lamont for the LHC Team
2011-01-01
The LHC is enjoying a confluence of twos. This morning (Friday 5 August) we passed 2 inverse femtobarns delivered in 2011; the peak luminosity is now just over 2 x1033 cm-2s-1; and recently fill 2000 was in for nearly 22 hours and delivered around 90 inverse picobarns, almost twice 2010's total. In order to increase the luminosity we can increase of number of bunches, increase the number of particles per bunch, or decrease the transverse beam size at the interaction point. The beam size can be tackled in two ways: either reduce the size of the injected bunches or squeeze harder with the quadrupole magnets situated on either side of the experiments. Having increased the number of bunches to 1380, the maximum possible with a 50 ns bunch spacing, a one day meeting in Crozet decided to explore the other possibilities. The size of the beams coming from the injectors has been reduced to the minimum possible. This has brought an increase in the peak luminosity of about 50% and the 2 x 1033 cm...
Inverse problems in systems biology
International Nuclear Information System (INIS)
Engl, Heinz W; Lu, James; Müller, Stefan; Flamm, Christoph; Schuster, Peter; Kügler, Philipp
2009-01-01
Systems biology is a new discipline built upon the premise that an understanding of how cells and organisms carry out their functions cannot be gained by looking at cellular components in isolation. Instead, consideration of the interplay between the parts of systems is indispensable for analyzing, modeling, and predicting systems' behavior. Studying biological processes under this premise, systems biology combines experimental techniques and computational methods in order to construct predictive models. Both in building and utilizing models of biological systems, inverse problems arise at several occasions, for example, (i) when experimental time series and steady state data are used to construct biochemical reaction networks, (ii) when model parameters are identified that capture underlying mechanisms or (iii) when desired qualitative behavior such as bistability or limit cycle oscillations is engineered by proper choices of parameter combinations. In this paper we review principles of the modeling process in systems biology and illustrate the ill-posedness and regularization of parameter identification problems in that context. Furthermore, we discuss the methodology of qualitative inverse problems and demonstrate how sparsity enforcing regularization allows the determination of key reaction mechanisms underlying the qualitative behavior. (topical review)
Inverse problems and inverse scattering of plane waves
Ghosh Roy, Dilip N
2001-01-01
The purpose of this text is to present the theory and mathematics of inverse scattering, in a simple way, to the many researchers and professionals who use it in their everyday research. While applications range across a broad spectrum of disciplines, examples in this text will focus primarly, but not exclusively, on acoustics. The text will be especially valuable for those applied workers who would like to delve more deeply into the fundamentally mathematical character of the subject matter.Practitioners in this field comprise applied physicists, engineers, and technologists, whereas the theory is almost entirely in the domain of abstract mathematics. This gulf between the two, if bridged, can only lead to improvement in the level of scholarship in this highly important discipline. This is the book''s primary focus.
Inverse geothermal modelling applied to Danish sedimentary basins
Poulsen, Søren E.; Balling, Niels; Bording, Thue S.; Mathiesen, Anders; Nielsen, Søren B.
2017-10-01
This paper presents a numerical procedure for predicting subsurface temperatures and heat-flow distribution in 3-D using inverse calibration methodology. The procedure is based on a modified version of the groundwater code MODFLOW by taking advantage of the mathematical similarity between confined groundwater flow (Darcy's law) and heat conduction (Fourier's law). Thermal conductivity, heat production and exponential porosity-depth relations are specified separately for the individual geological units of the model domain. The steady-state temperature model includes a model-based transient correction for the long-term palaeoclimatic thermal disturbance of the subsurface temperature regime. Variable model parameters are estimated by inversion of measured borehole temperatures with uncertainties reflecting their quality. The procedure facilitates uncertainty estimation for temperature predictions. The modelling procedure is applied to Danish onshore areas containing deep sedimentary basins. A 3-D voxel-based model, with 14 lithological units from surface to 5000 m depth, was built from digital geological maps derived from combined analyses of reflection seismic lines and borehole information. Matrix thermal conductivity of model lithologies was estimated by inversion of all available deep borehole temperature data and applied together with prescribed background heat flow to derive the 3-D subsurface temperature distribution. Modelled temperatures are found to agree very well with observations. The numerical model was utilized for predicting and contouring temperatures at 2000 and 3000 m depths and for two main geothermal reservoir units, the Gassum (Lower Jurassic-Upper Triassic) and Bunter/Skagerrak (Triassic) reservoirs, both currently utilized for geothermal energy production. Temperature gradients to depths of 2000-3000 m are generally around 25-30 °C km-1, locally up to about 35 °C km-1. Large regions have geothermal reservoirs with characteristic temperatures
Statistical Inversion of Seismic Noise Inversion statistique du bruit sismique
Directory of Open Access Journals (Sweden)
Adler P. M.
2006-11-01
Full Text Available A systematic investigation of wave propagation in random media is presented. Spectral analysis, inversion of codas and attenuation of the direct wave front are studied for synthetic data obtained in isotropic or anisotropic, 2D or 3D media. A coda inversion process is developed and checked on two sets of real data. In both cases, it is possible to compare the correlation lengths obtained by inversion to characteristic lengths measured on seismic logs, for the full scale seismic survey, or on a thin section, for the laboratory experiment. These two experiments prove the feasibility and the efficiency of the statistical inversion of codas. Correct characteristic lengths can be obtained which cannot be determined by another method. Le problème de la géophysique est la recherche d'informations concernant le sous-sol, dans des signaux sismiques enregistrés en surface ou dans des puits. Ces informations sont habituellement recherchées sous forme déterministe, c'est-à-dire sous la forme de la donnée en chaque point d'une valeur du paramètre étudié. Notre point de vue est différent puisque notre objectif est de déduire certaines propriétés statistiques du milieu, supposé hétérogène, à partir des sismogrammes enregistrés après propagation. Il apparaît alors deux moyens de remplir l'objectif fixé. Le premier est l'analyse spectrale des codas ; cette analyse permet de déterminer les tailles moyennes des hétérogénéités du sous-sol. La deuxième possibilité est l'étude de l'atténuation du front direct de l'onde, qui conduit aussi à la connaissance des longueurs caractéristiques du sous-sol ; contrairement à la première méthode, elle ne semble pas pouvoir être transposée efficacement à des cas réels. Dans la première partie, on teste numériquement la proportionnalité entre le facteur de rétrodiffraction, relié aux propriétés statistiques du milieu, et le spectre des codas. Les distributions de vitesse, à valeur
Solution for Ill-Posed Inverse Kinematics of Robot Arm by Network Inversion
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Takehiko Ogawa
2010-01-01
Full Text Available In the context of controlling a robot arm with multiple joints, the method of estimating the joint angles from the given end-effector coordinates is called inverse kinematics, which is a type of inverse problems. Network inversion has been proposed as a method for solving inverse problems by using a multilayer neural network. In this paper, network inversion is introduced as a method to solve the inverse kinematics problem of a robot arm with multiple joints, where the joint angles are estimated from the given end-effector coordinates. In general, inverse problems are affected by ill-posedness, which implies that the existence, uniqueness, and stability of their solutions are not guaranteed. In this paper, we show the effectiveness of applying network inversion with regularization, by which ill-posedness can be reduced, to the ill-posed inverse kinematics of an actual robot arm with multiple joints.
Directory of Open Access Journals (Sweden)
Mehdi Dehghan
2001-01-01
Full Text Available Two different finite difference schemes for solving the two-dimensional parabolic inverse problem with temperature overspecification are considered. These schemes are developed for indentifying the control parameter which produces, at any given time, a desired temperature distribution at a given point in the spatial domain. The numerical methods discussed, are based on the (3,3 alternating direction implicit (ADI finite difference scheme and the (3,9 alternating direction implicit formula. These schemes are unconditionally stable. The basis of analysis of the finite difference equation considered here is the modified equivalent partial differential equation approach, developed from the 1974 work of Warming and Hyett [17]. This allows direct and simple comparison of the errors associated with the equations as well as providing a means to develop more accurate finite difference schemes. These schemes use less central processor times than the fully implicit schemes for two-dimensional diffusion with temperature overspecification. The alternating direction implicit schemes developed in this report use more CPU times than the fully explicit finite difference schemes, but their unconditional stability is significant. The results of numerical experiments are presented, and accuracy and the Central Processor (CPU times needed for each of the methods are discussed. We also give error estimates in the maximum norm for each of these methods.
Inverse problem in neutron reflection
International Nuclear Information System (INIS)
Zhou, Xiao-Lin; Felcher, G.P.; Chen, Sow-Hsin
1991-05-01
Reflectance and transmittance of neutrons from a thin film deposited on a bulk substrate are derived from solution of Schroedinger wave equation in the material medium with an optical potential. A closed-form solution for the complex reflectance and transmittance is obtained in an approximation where the curvature of the scattering length density profile in the film is small. This closed-form solution reduces to all the known approximations in various limiting cases and is shown to be more accurate than the existing approximations. The closed-form solution of the reflectance is used as a starting point for an inversion algorithm whereby the reflectance data are inverted by a matrix iteration scheme to obtain the scattering length density distribution in the film. A preliminary test showed that the inverted profile is accurate for the linear scattering length density distribution but falls short in the case of an exponential distribution. 30 refs., 7 figs., 1 tab
Wake Vortex Inverse Model User's Guide
Lai, David; Delisi, Donald
2008-01-01
NorthWest Research Associates (NWRA) has developed an inverse model for inverting landing aircraft vortex data. The data used for the inversion are the time evolution of the lateral transport position and vertical position of both the port and starboard vortices. The inverse model performs iterative forward model runs using various estimates of vortex parameters, vertical crosswind profiles, and vortex circulation as a function of wake age. Forward model predictions of lateral transport and altitude are then compared with the observed data. Differences between the data and model predictions guide the choice of vortex parameter values, crosswind profile and circulation evolution in the next iteration. Iterations are performed until a user-defined criterion is satisfied. Currently, the inverse model is set to stop when the improvement in the rms deviation between the data and model predictions is less than 1 percent for two consecutive iterations. The forward model used in this inverse model is a modified version of the Shear-APA model. A detailed description of this forward model, the inverse model, and its validation are presented in a different report (Lai, Mellman, Robins, and Delisi, 2007). This document is a User's Guide for the Wake Vortex Inverse Model. Section 2 presents an overview of the inverse model program. Execution of the inverse model is described in Section 3. When executing the inverse model, a user is requested to provide the name of an input file which contains the inverse model parameters, the various datasets, and directories needed for the inversion. A detailed description of the list of parameters in the inversion input file is presented in Section 4. A user has an option to save the inversion results of each lidar track in a mat-file (a condensed data file in Matlab format). These saved mat-files can be used for post-inversion analysis. A description of the contents of the saved files is given in Section 5. An example of an inversion input
Accommodating chromosome inversions in linkage analysis.
Chen, Gary K; Slaten, Erin; Ophoff, Roel A; Lange, Kenneth
2006-08-01
This work develops a population-genetics model for polymorphic chromosome inversions. The model precisely describes how an inversion changes the nature of and approach to linkage equilibrium. The work also describes algorithms and software for allele-frequency estimation and linkage analysis in the presence of an inversion. The linkage algorithms implemented in the software package Mendel estimate recombination parameters and calculate the posterior probability that each pedigree member carries the inversion. Application of Mendel to eight Centre d'Etude du Polymorphisme Humain pedigrees in a region containing a common inversion on 8p23 illustrates its potential for providing more-precise estimates of the location of an unmapped marker or trait gene. Our expanded cytogenetic analysis of these families further identifies inversion carriers and increases the evidence of linkage.
Optimization and inverse problems in electromagnetism
Wiak, Sławomir
2003-01-01
From 12 to 14 September 2002, the Academy of Humanities and Economics (AHE) hosted the workshop "Optimization and Inverse Problems in Electromagnetism". After this bi-annual event, a large number of papers were assembled and combined in this book. During the workshop recent developments and applications in optimization and inverse methodologies for electromagnetic fields were discussed. The contributions selected for the present volume cover a wide spectrum of inverse and optimal electromagnetic methodologies, ranging from theoretical to practical applications. A number of new optimal and inverse methodologies were proposed. There are contributions related to dedicated software. Optimization and Inverse Problems in Electromagnetism consists of three thematic chapters, covering: -General papers (survey of specific aspects of optimization and inverse problems in electromagnetism), -Methodologies, -Industrial Applications. The book can be useful to students of electrical and electronics engineering, computer sci...
Including geological information in the inverse problem of palaeothermal reconstruction
Trautner, S.; Nielsen, S. B.
2003-04-01
A reliable reconstruction of sediment thermal history is of central importance to the assessment of hydrocarbon potential and the understanding of basin evolution. However, only rarely do sedimentation history and borehole data in the form of present day temperatures and vitrinite reflectance constrain the past thermal evolution to a useful level of accuracy (Gallagher and Sambridge,1992; Nielsen,1998; Trautner and Nielsen,2003). This is reflected in the inverse solutions to the problem of determining heat flow history from borehole data: The recent heat flow is constrained by data while older values are governed by the chosen a prior heat flow. In this paper we reduce this problem by including geological information in the inverse problem. Through a careful analysis of geological and geophysical data the timing of the tectonic processes, which may influence heat flow, can be inferred. The heat flow history is then parameterised to allow for the temporal variations characteristic of the different tectonic events. The inversion scheme applies a Markov chain Monte Carlo (MCMC) approach (Nielsen and Gallagher, 1999; Ferrero and Gallagher,2002), which efficiently explores the model space and futhermore samples the posterior probability distribution of the model. The technique is demonstrated on wells in the northern North Sea with emphasis on the stretching event in Late Jurassic. The wells are characterised by maximum sediment temperature at the present day, which is the worst case for resolution of the past thermal history because vitrinite reflectance is determined mainly by the maximum temperature. Including geological information significantly improves the thermal resolution. Ferrero, C. and Gallagher,K.,2002. Stochastic thermal history modelling.1. Constraining heat flow histories and their uncertainty. Marine and Petroleum Geology, 19, 633-648. Gallagher,K. and Sambridge, M., 1992. The resolution of past heat flow in sedimentary basins from non-linear inversion
Identifiability Scaling Laws in Bilinear Inverse Problems
Choudhary, Sunav; Mitra, Urbashi
2014-01-01
A number of ill-posed inverse problems in signal processing, like blind deconvolution, matrix factorization, dictionary learning and blind source separation share the common characteristic of being bilinear inverse problems (BIPs), i.e. the observation model is a function of two variables and conditioned on one variable being known, the observation is a linear function of the other variable. A key issue that arises for such inverse problems is that of identifiability, i.e. whether the observa...
Lectures on the inverse scattering method
International Nuclear Information System (INIS)
Zakharov, V.E.
1983-06-01
In a series of six lectures an elementary introduction to the theory of inverse scattering is given. The first four lectures contain a detailed theory of solitons in the framework of the KdV equation, together with the inverse scattering theory of the one-dimensional Schroedinger equation. In the fifth lecture the dressing method is described, while the sixth lecture gives a brief review of the equations soluble by the inverse scattering method. (author)
Inverse kinematics of OWI-535 robotic arm
DEBENEC, PRIMOŽ
2015-01-01
The thesis aims to calculate the inverse kinematics for the OWI-535 robotic arm. The calculation of the inverse kinematics determines the joint parameters that provide the right pose of the end effector. The pose consists of the position and orientation, however, we will focus only on the second one. Due to arm limitations, we have created our own type of the calculation of the inverse kinematics. At first we have derived it only theoretically, and then we have transferred the derivation into...
Automatic Flight Controller With Model Inversion
Meyer, George; Smith, G. Allan
1992-01-01
Automatic digital electronic control system based on inverse-model-follower concept being developed for proposed vertical-attitude-takeoff-and-landing airplane. Inverse-model-follower control places inverse mathematical model of dynamics of controlled plant in series with control actuators of controlled plant so response of combination of model and plant to command is unity. System includes feedback to compensate for uncertainties in mathematical model and disturbances imposed from without.
Inverse methods in thermomechanics: application to an industrial case
International Nuclear Information System (INIS)
Chau, T.H.; Morilhat, P.; Maye, J.P.
1993-01-01
For safety reasons, the measurements of nuclear piping temperature and stress variations during transients are mainly available in the outer side, while the highest values take place in the inner one. To solve this inverse problem, we propose a transfer function approach to link the spectra of inner and outer values. The unidimensional model, using an analytical identified transfer function, is carried out and checked in a real-like case. The results show that stress measurements are more reliable than temperature measurements for the estimation of inner temperature fluctuations. This is due to the integral effect, through thickness, of stress instead of the local effect of temperature. This method can also be used for 2D or 3D structures. However, in those cases, the transfer function cannot be estimated with analytical formulas. The transfer function is assessed by identification with the impulse response of the structure. (authors). 6 figs., 5 refs
On the inverse Magnus effect for flow past a rotating cylinder
John, Benzi; Gu, Xiao-Jun; Barber, Robert W.; Emerson, David R.
2016-11-01
Flow past a rotating cylinder has been investigated using the direct simulation Monte Carlo method. The study focuses on the occurrence of the inverse Magnus effect under subsonic flow conditions. In particular, the variations in the coefficients of lift and drag have been investigated as a function of the Knudsen and Reynolds numbers. Additionally, a temperature sensitivity study has been carried out to assess the influence of the wall temperature on the computed aerodynamic coefficients. It has been found that both the Reynolds number and the cylinder wall temperature significantly affect the drag as well as the onset of lift inversion in the transition flow regime.
Time-reversal and Bayesian inversion
Debski, Wojciech
2017-04-01
Probabilistic inversion technique is superior to the classical optimization-based approach in all but one aspects. It requires quite exhaustive computations which prohibit its use in huge size inverse problems like global seismic tomography or waveform inversion to name a few. The advantages of the approach are, however, so appealing that there is an ongoing continuous afford to make the large inverse task as mentioned above manageable with the probabilistic inverse approach. One of the perspective possibility to achieve this goal relays on exploring the internal symmetry of the seismological modeling problems in hand - a time reversal and reciprocity invariance. This two basic properties of the elastic wave equation when incorporating into the probabilistic inversion schemata open a new horizons for Bayesian inversion. In this presentation we discuss the time reversal symmetry property, its mathematical aspects and propose how to combine it with the probabilistic inverse theory into a compact, fast inversion algorithm. We illustrate the proposed idea with the newly developed location algorithm TRMLOC and discuss its efficiency when applied to mining induced seismic data.
Chromatid Painting for Chromosomal Inversion Detection Project
National Aeronautics and Space Administration — We propose the continued development of a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and...
Laterally constrained inversion for CSAMT data interpretation
Wang, Ruo; Yin, Changchun; Wang, Miaoyue; Di, Qingyun
2015-10-01
Laterally constrained inversion (LCI) has been successfully applied to the inversion of dc resistivity, TEM and airborne EM data. However, it hasn't been yet applied to the interpretation of controlled-source audio-frequency magnetotelluric (CSAMT) data. In this paper, we apply the LCI method for CSAMT data inversion by preconditioning the Jacobian matrix. We apply a weighting matrix to Jacobian to balance the sensitivity of model parameters, so that the resolution with respect to different model parameters becomes more uniform. Numerical experiments confirm that this can improve the convergence of the inversion. We first invert a synthetic dataset with and without noise to investigate the effect of LCI applications to CSAMT data, for the noise free data, the results show that the LCI method can recover the true model better compared to the traditional single-station inversion; and for the noisy data, the true model is recovered even with a noise level of 8%, indicating that LCI inversions are to some extent noise insensitive. Then, we re-invert two CSAMT datasets collected respectively in a watershed and a coal mine area in Northern China and compare our results with those from previous inversions. The comparison with the previous inversion in a coal mine shows that LCI method delivers smoother layer interfaces that well correlate to seismic data, while comparison with a global searching algorithm of simulated annealing (SA) in a watershed shows that though both methods deliver very similar good results, however, LCI algorithm presented in this paper runs much faster. The inversion results for the coal mine CSAMT survey show that a conductive water-bearing zone that was not revealed by the previous inversions has been identified by the LCI. This further demonstrates that the method presented in this paper works for CSAMT data inversion.
Magnetic catalysis and inverse magnetic catalysis in QCD
International Nuclear Information System (INIS)
Mueller, N.
2015-01-01
We investigate the effects of strong magnetic fields on the QCD phase structure at vanishing density by solving the gluon and quark gap equations. The chiral crossover temperature as well as the chiral condensate is computed. For asymptotically large magnetic fields we find magnetic catalysis, while we find inverse magnetic catalysis for intermediate magnetic fields. Moreover, for large magnetic fields the chiral phase transition for massless quarks turns into a crossover. The underlying mechanisms are then investigated analytically within a few simplifications of the full numerical analysis. We find that a combination of gluon screening effects and the weakening of the strong coupling is responsible for the phenomenon of inverse catalysis seen in lattice studies. In turn, the magnetic catalysis at large magnetic field is already indicated by simple arguments based on dimensionality. (author)
Radiative-conductive inverse problem for lumped parameter systems
International Nuclear Information System (INIS)
Alifanov, O M; Nenarokomov, A V; Gonzalez, V M
2008-01-01
The purpose of this paper is to introduce a iterative regularization method in the research of radiative and thermal properties of materials with applications in the design of Thermal Control Systems (TCS) of spacecrafts. In this paper the radiative and thermal properties (emissivity and thermal conductance) of a multilayered thermal-insulating blanket (MLI), which is a screen-vacuum thermal insulation as a part of the (TCS) for perspective spacecrafts, are estimated. Properties of the materials under study are determined in the result of temperature and heat flux measurement data processing based on the solution of the Inverse Heat Transfer Problem (IHTP) technique. Given are physical and mathematical models of heat transfer processes in a specimen of the multilayered thermal-insulating blanket located in the experimental facility. A mathematical formulation of the inverse heat conduction problem is presented too. The practical testing were performed for specimen of the real MLI.
A variational Bayesian method to inverse problems with impulsive noise
Jin, Bangti
2012-01-01
We propose a novel numerical method for solving inverse problems subject to impulsive noises which possibly contain a large number of outliers. The approach is of Bayesian type, and it exploits a heavy-tailed t distribution for data noise to achieve robustness with respect to outliers. A hierarchical model with all hyper-parameters automatically determined from the given data is described. An algorithm of variational type by minimizing the Kullback-Leibler divergence between the true posteriori distribution and a separable approximation is developed. The numerical method is illustrated on several one- and two-dimensional linear and nonlinear inverse problems arising from heat conduction, including estimating boundary temperature, heat flux and heat transfer coefficient. The results show its robustness to outliers and the fast and steady convergence of the algorithm. © 2011 Elsevier Inc.
Chromospheric Inversions of a Micro-flaring Region
Energy Technology Data Exchange (ETDEWEB)
Reid, A.; Henriques, V.; Mathioudakis, M. [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN, Northern Ireland (United Kingdom); Doyle, J. G. [Armagh Observatory and Planetarium, College Hill, Armagh, BT61 9DG (United Kingdom); Ray, T., E-mail: aaron.reid@qub.ac.uk [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)
2017-08-20
We use spectropolarimetric observations of the Ca ii 8542 Å line, taken from the Swedish 1 m Solar Telescope, in an attempt to recover dynamic activity in a micro-flaring region near a sunspot via inversions. These inversions show localized mean temperature enhancements of ∼1000 K in the chromosphere and upper photosphere, along with co-spatial bi-directional Doppler shifting of 5–10 km s{sup −1}. This heating also extends along a nearby chromospheric fibril, which is co-spatial to 10–15 km s{sup −1} downflows. Strong magnetic flux cancellation is also apparent in one of the footpoints, and is concentrated in the chromosphere. This event more closely resembles that of an Ellerman Bomb, though placed slightly higher in the atmosphere than what is typically observed.
Numerical investigation of the inverse blackbody radiation problem
International Nuclear Information System (INIS)
Xin Tan, Guo-zhen Yang, Ben-yuan Gu
1994-01-01
A numerical algorithm for the inverse blackbody radiation problem, which is the determination of the temperature distribution of a thermal radiator (TDTR) from its total radiated power spectrum (TRPS), is presented, based on the general theory of amplitude-phase retrieval. With application of this new algorithm, the ill-posed nature of the Fredholm equation of the first kind can be largely overcome and a convergent solution to high accuracy can be obtained. By incorporation of the hybrid input-output algorithm into our algorithm, the convergent process can be substantially expedited and the stagnation problem of the solution can be averted. From model calculations it is found that the new algorithm can also provide a robust reconstruction of the TDTR from the noise-corrupted data of the TRPS. Therefore the new algorithm may offer a useful approach to solving the ill-posed inverse problem. 18 refs., 9 figs
Inverse problems and uncertainty quantification
Litvinenko, Alexander
2013-12-18
In a Bayesian setting, inverse problems and uncertainty quantification (UQ)— the propagation of uncertainty through a computational (forward) model—are strongly connected. In the form of conditional expectation the Bayesian update becomes computationally attractive. This is especially the case as together with a functional or spectral approach for the forward UQ there is no need for time- consuming and slowly convergent Monte Carlo sampling. The developed sampling- free non-linear Bayesian update is derived from the variational problem associated with conditional expectation. This formulation in general calls for further discretisa- tion to make the computation possible, and we choose a polynomial approximation. After giving details on the actual computation in the framework of functional or spectral approximations, we demonstrate the workings of the algorithm on a number of examples of increasing complexity. At last, we compare the linear and quadratic Bayesian update on the small but taxing example of the chaotic Lorenz 84 model, where we experiment with the influence of different observation or measurement operators on the update.
Package inspection using inverse diffraction
McAulay, Alastair D.
2008-08-01
More efficient cost-effective hand-held methods of inspecting packages without opening them are in demand for security. Recent new work in TeraHertz sources,1 millimeter waves, presents new possibilities. Millimeter waves pass through cardboard and styrofoam, common packing materials, and also pass through most materials except those with high conductivity like metals which block light and are easily spotted. Estimating refractive index along the path of the beam through the package from observations of the beam passing out of the package provides the necessary information to inspect the package and is a nonlinear problem. So we use a generalized linear inverse technique that we first developed for finding oil by reflection in geophysics.2 The computation assumes parallel slices in the packet of homogeneous material for which the refractive index is estimated. A beam is propagated through this model in a forward computation. The output is compared with the actual observations for the package and an update computed for the refractive indices. The loop is repeated until convergence. The approach can be modified for a reflection system or to include estimation of absorption.
MODEL SELECTION FOR SPECTROPOLARIMETRIC INVERSIONS
International Nuclear Information System (INIS)
Asensio Ramos, A.; Manso Sainz, R.; Martínez González, M. J.; Socas-Navarro, H.; Viticchié, B.; Orozco Suárez, D.
2012-01-01
Inferring magnetic and thermodynamic information from spectropolarimetric observations relies on the assumption of a parameterized model atmosphere whose parameters are tuned by comparison with observations. Often, the choice of the underlying atmospheric model is based on subjective reasons. In other cases, complex models are chosen based on objective reasons (for instance, the necessity to explain asymmetries in the Stokes profiles) but it is not clear what degree of complexity is needed. The lack of an objective way of comparing models has, sometimes, led to opposing views of the solar magnetism because the inferred physical scenarios are essentially different. We present the first quantitative model comparison based on the computation of the Bayesian evidence ratios for spectropolarimetric observations. Our results show that there is not a single model appropriate for all profiles simultaneously. Data with moderate signal-to-noise ratios (S/Ns) favor models without gradients along the line of sight. If the observations show clear circular and linear polarization signals above the noise level, models with gradients along the line are preferred. As a general rule, observations with large S/Ns favor more complex models. We demonstrate that the evidence ratios correlate well with simple proxies. Therefore, we propose to calculate these proxies when carrying out standard least-squares inversions to allow for model comparison in the future.
Inverse Problems and Uncertainty Quantification
Litvinenko, Alexander
2014-01-06
In a Bayesian setting, inverse problems and uncertainty quantification (UQ) - the propagation of uncertainty through a computational (forward) modelare strongly connected. In the form of conditional expectation the Bayesian update becomes computationally attractive. This is especially the case as together with a functional or spectral approach for the forward UQ there is no need for time- consuming and slowly convergent Monte Carlo sampling. The developed sampling- free non-linear Bayesian update is derived from the variational problem associated with conditional expectation. This formulation in general calls for further discretisa- tion to make the computation possible, and we choose a polynomial approximation. After giving details on the actual computation in the framework of functional or spectral approximations, we demonstrate the workings of the algorithm on a number of examples of increasing complexity. At last, we compare the linear and quadratic Bayesian update on the small but taxing example of the chaotic Lorenz 84 model, where we experiment with the influence of different observation or measurement operators on the update.
Inverse problem in radionuclide transport
International Nuclear Information System (INIS)
Yu, C.
1988-01-01
The disposal of radioactive waste must comply with the performance objectives set forth in 10 CFR 61 for low-level waste (LLW) and 10 CFR 60 for high-level waste (HLW). To determine probable compliance, the proposed disposal system can be modeled to predict its performance. One of the difficulties encountered in such a study is modeling the migration of radionuclides through a complex geologic medium for the long term. Although many radionuclide transport models exist in the literature, the accuracy of the model prediction is highly dependent on the model parameters used. The problem of using known parameters in a radionuclide transport model to predict radionuclide concentrations is a direct problem (DP); whereas the reverse of DP, i.e., the parameter identification problem of determining model parameters from known radionuclide concentrations, is called the inverse problem (IP). In this study, a procedure to solve IP is tested, using the regression technique. Several nonlinear regression programs are examined, and the best one is recommended. 13 refs., 1 tab
Reverse Universal Resolving Algorithm and inverse driving
DEFF Research Database (Denmark)
Pécseli, Thomas
2012-01-01
Inverse interpretation is a semantics based, non-standard interpretation of programs. Given a program and a value, an inverse interpreter finds all or one of the inputs, that would yield the given value as output with normal forward evaluation. The Reverse Universal Resolving Algorithm is a new v...
Third Harmonic Imaging using a Pulse Inversion
DEFF Research Database (Denmark)
Rasmussen, Joachim; Du, Yigang; Jensen, Jørgen Arendt
2011-01-01
The pulse inversion (PI) technique can be utilized to separate and enhance harmonic components of a waveform for tissue harmonic imaging. While most ultrasound systems can perform pulse inversion, only few image the 3rd harmonic component. PI pulse subtraction can isolate and enhance the 3rd...
Metaheuristic optimization of acoustic inverse problems.
van Leijen, A.V.; Rothkrantz, L.; Groen, F.
2011-01-01
Swift solving of geoacoustic inverse problems strongly depends on the application of a global optimization scheme. Given a particular inverse problem, this work aims to answer the questions how to select an appropriate metaheuristic search strategy, and how to configure it for optimal performance.
Inverse Filtering Techniques in Speech Analysis | Nwachuku ...
African Journals Online (AJOL)
inverse filtering' has been applied. The unifying features of these techniques are presented, namely: 1. a basis in the source-filter theory of speech production, 2. the use of a network whose transfer function is the inverse of the transfer function of ...
Inverse m-matrices and ultrametric matrices
Dellacherie, Claude; San Martin, Jaime
2014-01-01
The study of M-matrices, their inverses and discrete potential theory is now a well-established part of linear algebra and the theory of Markov chains. The main focus of this monograph is the so-called inverse M-matrix problem, which asks for a characterization of nonnegative matrices whose inverses are M-matrices. We present an answer in terms of discrete potential theory based on the Choquet-Deny Theorem. A distinguished subclass of inverse M-matrices is ultrametric matrices, which are important in applications such as taxonomy. Ultrametricity is revealed to be a relevant concept in linear algebra and discrete potential theory because of its relation with trees in graph theory and mean expected value matrices in probability theory. Remarkable properties of Hadamard functions and products for the class of inverse M-matrices are developed and probabilistic insights are provided throughout the monograph.
Fast wavelet based sparse approximate inverse preconditioner
Energy Technology Data Exchange (ETDEWEB)
Wan, W.L. [Univ. of California, Los Angeles, CA (United States)
1996-12-31
Incomplete LU factorization is a robust preconditioner for both general and PDE problems but unfortunately not easy to parallelize. Recent study of Huckle and Grote and Chow and Saad showed that sparse approximate inverse could be a potential alternative while readily parallelizable. However, for special class of matrix A that comes from elliptic PDE problems, their preconditioners are not optimal in the sense that independent of mesh size. A reason may be that no good sparse approximate inverse exists for the dense inverse matrix. Our observation is that for this kind of matrices, its inverse entries typically have piecewise smooth changes. We can take advantage of this fact and use wavelet compression techniques to construct a better sparse approximate inverse preconditioner. We shall show numerically that our approach is effective for this kind of matrices.
Solving inverse problems of optical microlithography
Granik, Yuri
2005-05-01
The direct problem of microlithography is to simulate printing features on the wafer under given mask, imaging system, and process characteristics. The goal of inverse problems is to find the best mask and/or imaging system and/or process to print the given wafer features. In this study we will describe and compare solutions of inverse mask problems. Pixel-based inverse problem of mask optimization (or "layout inversion") is harder than inverse source problem, especially for partially-coherent systems. It can be stated as a non-linear constrained minimization problem over complex domain, with large number of variables. We compare method of Nashold projections, variations of Fienap phase-retrieval algorithms, coherent approximation with deconvolution, local variations, and descent searches. We propose electrical field caching technique to substantially speedup the searching algorithms. We demonstrate applications of phase-shifted masks, assist features, and maskless printing.
Recurrent Neural Network for Computing Outer Inverse.
Živković, Ivan S; Stanimirović, Predrag S; Wei, Yimin
2016-05-01
Two linear recurrent neural networks for generating outer inverses with prescribed range and null space are defined. Each of the proposed recurrent neural networks is based on the matrix-valued differential equation, a generalization of dynamic equations proposed earlier for the nonsingular matrix inversion, the Moore-Penrose inversion, as well as the Drazin inversion, under the condition of zero initial state. The application of the first approach is conditioned by the properties of the spectrum of a certain matrix; the second approach eliminates this drawback, though at the cost of increasing the number of matrix operations. The cases corresponding to the most common generalized inverses are defined. The conditions that ensure stability of the proposed neural network are presented. Illustrative examples present the results of numerical simulations.
Forward modeling. Route to electromagnetic inversion
Energy Technology Data Exchange (ETDEWEB)
Groom, R.; Walker, P. [PetRos EiKon Incorporated, Ontario (Canada)
1996-05-01
Inversion of electromagnetic data is a topical subject in the literature, and much time has been devoted to understanding the convergence properties of various inverse methods. The relative lack of success of electromagnetic inversion techniques is partly attributable to the difficulties in the kernel forward modeling software. These difficulties come in two broad classes: (1) Completeness and robustness, and (2) convergence, execution time and model simplicity. If such problems exist in the forward modeling kernel, it was demonstrated that inversion can fail to generate reasonable results. It was suggested that classical inversion techniques, which are based on minimizing a norm of the error between data and the simulated data, will only be successful when these difficulties in forward modeling kernels are properly dealt with. 4 refs., 5 figs.
Stochastic Gabor reflectivity and acoustic impedance inversion
Hariri Naghadeh, Diako; Morley, Christopher Keith; Ferguson, Angus John
2018-02-01
To delineate subsurface lithology to estimate petrophysical properties of a reservoir, it is possible to use acoustic impedance (AI) which is the result of seismic inversion. To change amplitude to AI, removal of wavelet effects from the seismic signal in order to get a reflection series, and subsequently transforming those reflections to AI, is vital. To carry out seismic inversion correctly it is important to not assume that the seismic signal is stationary. However, all stationary deconvolution methods are designed following that assumption. To increase temporal resolution and interpretation ability, amplitude compensation and phase correction are inevitable. Those are pitfalls of stationary reflectivity inversion. Although stationary reflectivity inversion methods are trying to estimate reflectivity series, because of incorrect assumptions their estimations will not be correct, but may be useful. Trying to convert those reflection series to AI, also merging with the low frequency initial model, can help us. The aim of this study was to apply non-stationary deconvolution to eliminate time variant wavelet effects from the signal and to convert the estimated reflection series to the absolute AI by getting bias from well logs. To carry out this aim, stochastic Gabor inversion in the time domain was used. The Gabor transform derived the signal’s time–frequency analysis and estimated wavelet properties from different windows. Dealing with different time windows gave an ability to create a time-variant kernel matrix, which was used to remove matrix effects from seismic data. The result was a reflection series that does not follow the stationary assumption. The subsequent step was to convert those reflections to AI using well information. Synthetic and real data sets were used to show the ability of the introduced method. The results highlight that the time cost to get seismic inversion is negligible related to general Gabor inversion in the frequency domain. Also
Developments in inverse photoemission spectroscopy
International Nuclear Information System (INIS)
Sheils, W.; Leckey, R.C.G.; Riley, J.D.
1996-01-01
In the 1950's and 1960's, Photoemission Spectroscopy (PES) established itself as the major technique for the study of the occupied electronic energy levels of solids. During this period the field divided into two branches: X-ray Photoemission Spectroscopy (XPS) for photon energies greater than ∼l000eV, and Ultra-violet Photoemission Spectroscopy (UPS) for photon energies below ∼100eV. By the 1970's XPS and UPS had become mature techniques. Like XPS, BIS (at x-ray energies) does not have the momentum-resolving ability of UPS that has contributed much to the understanding of the occupied band structures of solids. BIS moved into a new energy regime in 1977 when Dose employed a Geiger-Mueller tube to obtain density of unoccupied states data from a tantalum sample at a photon energy of ∼9.7eV. At similar energies, the technique has since become known as Inverse Photoemission Spectroscopy (IPS), in acknowledgment of its complementary relationship to UPS and to distinguish it from the higher energy BIS. Drawing on decades of UPS expertise, IPS has quickly moved into areas of interest where UPS has been applied; metals, semiconductors, layer compounds, adsorbates, ferromagnets, and superconductors. At La Trobe University an IPS facility has been constructed. This presentation reports on developments in the experimental and analytical techniques of IPS that have been made there. The results of a study of the unoccupied bulk and surface bands of GaAs are presented
Inverse magnetic catalysis in Nambu–Jona-Lasinio model beyond mean field
International Nuclear Information System (INIS)
Mao, Shijun
2016-01-01
We study inverse magnetic catalysis in the Nambu–Jona-Lasinio model beyond mean field approximation. The feed-down from mesons to quarks is embedded in an effective coupling constant at finite temperature and magnetic field. While the magnetic catalysis is still the dominant effect at low temperature, the meson dressed quark mass drops down with increasing magnetic field at high temperature due to the dimension reduction of the Goldstone mode in the Pauli–Villars regularization scheme.
Convex blind image deconvolution with inverse filtering
Lv, Xiao-Guang; Li, Fang; Zeng, Tieyong
2018-03-01
Blind image deconvolution is the process of estimating both the original image and the blur kernel from the degraded image with only partial or no information about degradation and the imaging system. It is a bilinear ill-posed inverse problem corresponding to the direct problem of convolution. Regularization methods are used to handle the ill-posedness of blind deconvolution and get meaningful solutions. In this paper, we investigate a convex regularized inverse filtering method for blind deconvolution of images. We assume that the support region of the blur object is known, as has been done in a few existing works. By studying the inverse filters of signal and image restoration problems, we observe the oscillation structure of the inverse filters. Inspired by the oscillation structure of the inverse filters, we propose to use the star norm to regularize the inverse filter. Meanwhile, we use the total variation to regularize the resulting image obtained by convolving the inverse filter with the degraded image. The proposed minimization model is shown to be convex. We employ the first-order primal-dual method for the solution of the proposed minimization model. Numerical examples for blind image restoration are given to show that the proposed method outperforms some existing methods in terms of peak signal-to-noise ratio (PSNR), structural similarity (SSIM), visual quality and time consumption.
3rd Annual Workshop on Inverse Problem
2015-01-01
This proceeding volume is based on papers presented on the Third Annual Workshop on Inverse Problems which was organized by the Department of Mathematical Sciences, Chalmers University of Technology and University of Gothenburg, and took place in May 2013 in Stockholm. The purpose of this workshop was to present new analytical developments and numerical techniques for solution of inverse problems for a wide range of applications in acoustics, electromagnetics, optical fibers, medical imaging, geophysics, etc. The contributions in this volume reflect these themes and will be beneficial to researchers who are working in the area of applied inverse problems.
Inverse Raman effect: applications and detection techniques
International Nuclear Information System (INIS)
Hughes, L.J. Jr.
1980-08-01
The processes underlying the inverse Raman effect are qualitatively described by comparing it to the more familiar phenomena of conventional and stimulated Raman scattering. An experession is derived for the inverse Raman absorption coefficient, and its relationship to the stimulated Raman gain is obtained. The power requirements of the two fields are examined qualitatively and quantitatively. The assumption that the inverse Raman absorption coefficient is constant over the interaction length is examined. Advantages of the technique are discussed and a brief survey of reported studies is presented
Inverse Raman effect: applications and detection techniques
Energy Technology Data Exchange (ETDEWEB)
Hughes, L.J. Jr.
1980-08-01
The processes underlying the inverse Raman effect are qualitatively described by comparing it to the more familiar phenomena of conventional and stimulated Raman scattering. An experession is derived for the inverse Raman absorption coefficient, and its relationship to the stimulated Raman gain is obtained. The power requirements of the two fields are examined qualitatively and quantitatively. The assumption that the inverse Raman absorption coefficient is constant over the interaction length is examined. Advantages of the technique are discussed and a brief survey of reported studies is presented.
Multiparameter Optimization for Electromagnetic Inversion Problem
Directory of Open Access Journals (Sweden)
M. Elkattan
2017-10-01
Full Text Available Electromagnetic (EM methods have been extensively used in geophysical investigations such as mineral and hydrocarbon exploration as well as in geological mapping and structural studies. In this paper, we developed an inversion methodology for Electromagnetic data to determine physical parameters of a set of horizontal layers. We conducted Forward model using transmission line method. In the inversion part, we solved multi parameter optimization problem where, the parameters are conductivity, dielectric constant, and permeability of each layer. The optimization problem was solved by simulated annealing approach. The inversion methodology was tested using a set of models representing common geological formations.
Population inversion in a stationary recombining plasma
International Nuclear Information System (INIS)
Otsuka, M.
1980-01-01
Population inversion, which occurs in a recombining plasma when a stationary He plasma is brought into contact with a neutral gas, is examined. With hydrogen as a contact gas, noticeable inversion between low-lying levels of H as been found. The overpopulation density is of the order of 10 8 cm -3 , which is much higher then that (approx. =10 5 cm -3 ) obtained previously with He as a contact gas. Relations between these experimental results and the conditions for population inversion are discussed with the CR model
Inverse design methods for radiative transfer systems
International Nuclear Information System (INIS)
Daun, K.J.; Howell, J.R.
2005-01-01
Radiant enclosures used in industrial processes have traditionally been designed by trial-and-error, a technique that usually demands considerable time to find a solution of limited quality. As an alternative, designers have recently adopted optimization and inverse methodologies to solve design problems involving radiative transfer; the optimization methodology solves the inverse problem implicitly by transforming it into a multivariable minimization problem, while the inverse design methodology solves the problem explicitly using regularization. This paper presents the details of both methodologies, and demonstrates them by solving for the optimal heater settings in an industrially relevant radiant enclosure design problem
The factorization method for inverse problems
Kirsch, Andreas
2008-01-01
The factorization method is a relatively new method for solving certain types of inverse scattering problems and problems in tomography. Aimed at students and researchers in Applied Mathematics, Physics and Engineering, this text introduces the reader to this promising approach for solving important classes of inverse problems. The wide applicability of this method is discussed by choosing typical examples, such as inverse scattering problems for the scalar Helmholtz equation, ascattering problem for Maxwell's equation, and a problem in impedance and optical tomography. The last section of the
Geoacoustic inversion using combustive sound source signals.
Potty, Gopu R; Miller, James H; Wilson, Preston S; Lynch, James F; Newhall, Arthur
2008-09-01
Combustive sound source (CSS) data collected on single hydrophone receiving units, in water depths ranging from 65 to 110 m, during the Shallow Water 2006 experiment clearly show modal dispersion effects and are suitable for modal geoacoustic inversions. CSS shots were set off at 26 m depth in 100 m of water. The inversions performed are based on an iterative scheme using dispersion-based short time Fourier transform in which each time-frequency tiling is adaptively rotated in the time-frequency plane, depending on the local wave dispersion. Results of the inversions are found to compare favorably to local core data.
BOOK REVIEW: Inverse Problems. Activities for Undergraduates
Yamamoto, Masahiro
2003-06-01
This book is a valuable introduction to inverse problems. In particular, from the educational point of view, the author addresses the questions of what constitutes an inverse problem and how and why we should study them. Such an approach has been eagerly awaited for a long time. Professor Groetsch, of the University of Cincinnati, is a world-renowned specialist in inverse problems, in particular the theory of regularization. Moreover, he has made a remarkable contribution to educational activities in the field of inverse problems, which was the subject of his previous book (Groetsch C W 1993 Inverse Problems in the Mathematical Sciences (Braunschweig: Vieweg)). For this reason, he is one of the most qualified to write an introductory book on inverse problems. Without question, inverse problems are important, necessary and appear in various aspects. So it is crucial to introduce students to exercises in inverse problems. However, there are not many introductory books which are directly accessible by students in the first two undergraduate years. As a consequence, students often encounter diverse concrete inverse problems before becoming aware of their general principles. The main purpose of this book is to present activities to allow first-year undergraduates to learn inverse theory. To my knowledge, this book is a rare attempt to do this and, in my opinion, a great success. The author emphasizes that it is very important to teach inverse theory in the early years. He writes; `If students consider only the direct problem, they are not looking at the problem from all sides .... The habit of always looking at problems from the direct point of view is intellectually limiting ...' (page 21). The book is very carefully organized so that teachers will be able to use it as a textbook. After an introduction in chapter 1, sucessive chapters deal with inverse problems in precalculus, calculus, differential equations and linear algebra. In order to let one gain some insight
Electron correlation effects on magnetism in superconductors without inversion symmetry
International Nuclear Information System (INIS)
Fujimoto, Satoshi
2007-01-01
We investigate magnetic properties of superconductors without inversion symmetry with particular emphasis on the role played by electron correlation effects. It is found that the strong electron correlation seriously affects the temperature dependence of the spin susceptibility which consists of the Pauli term and the van-Vleck-like term, of which the existence is due to parity violating spin-orbit interaction. The implication of the results for the recent NMR measurement of the heavy fermion superconductor CePt 3 Si, which indicates the unchanged Knight shift below T c for any directions of a magnetic field, is presented
From inverse problems to learning: a Statistical Mechanics approach
Baldassi, Carlo; Gerace, Federica; Saglietti, Luca; Zecchina, Riccardo
2018-01-01
We present a brief introduction to the statistical mechanics approaches for the study of inverse problems in data science. We then provide concrete new results on inferring couplings from sampled configurations in systems characterized by an extensive number of stable attractors in the low temperature regime. We also show how these result are connected to the problem of learning with realistic weak signals in computational neuroscience. Our techniques and algorithms rely on advanced mean-field methods developed in the context of disordered systems.
Two radiative inverse seesaw models, dark matter, and baryogenesis
International Nuclear Information System (INIS)
Baldes, Iason; Bell, Nicole F.; Petraki, Kalliopi; Volkas, Raymond R.
2013-01-01
The inverse seesaw mechanism allows the neutrino masses to be generated by new physics at an experimentally accessible scale, even with O(1) Yukawa couplings. In the inverse seesaw scenario, the smallness of neutrino masses is linked to the smallness of a lepton number violating parameter. This parameter may arise radiatively. In this paper, we study the cosmological implications of two contrasting radiative inverse seesaw models, one due to Ma and the other to Law and McDonald. The former features spontaneous, the latter explicit lepton number violation. First, we examine the effect of the lepton-number violating interactions introduced in these models on the baryon asymmetry of the universe. We investigate under what conditions a pre-existing baryon asymmetry does not get washed out. While both models allow a baryon asymmetry to survive only once the temperature has dropped below the mass of their heaviest fields, the Ma model can create the baryon asymmetry through resonant leptogenesis. Then we investigate the viability of the dark matter candidates arising within these models, and explore the prospects for direct detection. We find that the Law/McDonald model allows a simple dark matter scenario similar to the Higgs portal, while in the Ma model the simplest cold dark matter scenario would tend to overclose the universe
Dushaw, Brian D; Sagen, Hanne
2017-12-01
Ocean acoustic tomography depends on a suitable reference ocean environment with which to set the basic parameters of the inverse problem. Some inverse problems may require a reference ocean that includes the small-scale variations from internal waves, small mesoscale, or spice. Tomographic inversions that employ data of stable shadow zone arrivals, such as those that have been observed in the North Pacific and Canary Basin, are an example. Estimating temperature from the unique acoustic data that have been obtained in Fram Strait is another example. The addition of small-scale variability to augment a smooth reference ocean is essential to understanding the acoustic forward problem in these cases. Rather than a hindrance, the stochastic influences of the small scale can be exploited to obtain accurate inverse estimates. Inverse solutions are readily obtained, and they give computed arrival patterns that matched the observations. The approach is not ad hoc, but universal, and it has allowed inverse estimates for ocean temperature variations in Fram Strait to be readily computed on several acoustic paths for which tomographic data were obtained.
Sensitivity analyses of acoustic impedance inversion with full-waveform inversion
Yao, Gang; da Silva, Nuno V.; Wu, Di
2018-04-01
Acoustic impedance estimation has a significant importance to seismic exploration. In this paper, we use full-waveform inversion to recover the impedance from seismic data, and analyze the sensitivity of the acoustic impedance with respect to the source-receiver offset of seismic data and to the initial velocity model. We parameterize the acoustic wave equation with velocity and impedance, and demonstrate three key aspects of acoustic impedance inversion. First, short-offset data are most suitable for acoustic impedance inversion. Second, acoustic impedance inversion is more compatible with the data generated by density contrasts than velocity contrasts. Finally, acoustic impedance inversion requires the starting velocity model to be very accurate for achieving a high-quality inversion. Based upon these observations, we propose a workflow for acoustic impedance inversion as: (1) building a background velocity model with travel-time tomography or reflection waveform inversion; (2) recovering the intermediate wavelength components of the velocity model with full-waveform inversion constrained by Gardner’s relation; (3) inverting the high-resolution acoustic impedance model with short-offset data through full-waveform inversion. We verify this workflow by the synthetic tests based on the Marmousi model.
Full traveltime inversion in source domain
Liu, Lu
2017-06-01
This paper presents a new method of source-domain full traveltime inversion (FTI). The objective of this study is automatically building near-surface velocity using the early arrivals of seismic data. This method can generate the inverted velocity that can kinetically best match the reconstructed plane-wave source of early arrivals with true source in source domain. It does not require picking first arrivals for tomography, which is one of the most challenging aspects of ray-based tomographic inversion. Besides, this method does not need estimate the source wavelet, which is a necessity for receiver-domain wave-equation velocity inversion. Furthermore, we applied our method on one synthetic dataset; the results show our method could generate a reasonable background velocity even when shingling first arrivals exist and could provide a good initial velocity for the conventional full waveform inversion (FWI).
n-Colour self-inverse compositions
Indian Academy of Sciences (India)
colour self-inverse composition. This introduces four new sequences which satisfy the same recurrence relation with different initial conditions like the famous Fibonacci and Lucas sequences. For these new sequences explicit formulas, recurrence ...
Inverse Doppler Effects in Broadband Acoustic Metamaterials.
Zhai, S L; Zhao, X P; Liu, S; Shen, F L; Li, L L; Luo, C R
2016-08-31
The Doppler effect refers to the change in frequency of a wave source as a consequence of the relative motion between the source and an observer. Veselago theoretically predicted that materials with negative refractions can induce inverse Doppler effects. With the development of metamaterials, inverse Doppler effects have been extensively investigated. However, the ideal material parameters prescribed by these metamaterial design approaches are complex and also challenging to obtain experimentally. Here, we demonstrated a method of designing and experimentally characterising arbitrary broadband acoustic metamaterials. These omni-directional, double-negative, acoustic metamaterials are constructed with 'flute-like' acoustic meta-cluster sets with seven double meta-molecules; these metamaterials also overcome the limitations of broadband negative bulk modulus and mass density to provide a region of negative refraction and inverse Doppler effects. It was also shown that inverse Doppler effects can be detected in a flute, which has been popular for thousands of years in Asia and Europe.
n-Colour self-inverse compositions
Indian Academy of Sciences (India)
inverse composition. This introduces four new sequences which satisfy the same recurrence relation with different initial conditions like the famous Fibonacci and Lucas sequences. For these new sequences explicit formulas, recurrence relations ...
Parametric optimization of inverse trapezoid oleophobic surfaces
DEFF Research Database (Denmark)
Cavalli, Andrea; Bøggild, Peter; Okkels, Fridolin
2012-01-01
In this paper, we introduce a comprehensive and versatile approach to the parametric shape optimization of oleophobic surfaces. We evaluate the performance of inverse trapezoid microstructures in terms of three objective parameters: apparent contact angle, maximum sustainable hydrostatic pressure...
An inverse method for radiation transport
Energy Technology Data Exchange (ETDEWEB)
Favorite, J. A. (Jeffrey A.); Sanchez, R. (Richard)
2004-01-01
Adjoint functions have been used with forward functions to compute gradients in implicit (iterative) solution methods for inverse problems in optical tomography, geoscience, thermal science, and other fields, but only once has this approach been used for inverse solutions to the Boltzmann transport equation. In this paper, this approach is used to develop an inverse method that requires only angle-independent flux measurements, rather than angle-dependent measurements as was done previously. The method is applied to a simplified form of the transport equation that does not include scattering. The resulting procedure uses measured values of gamma-ray fluxes of discrete, characteristic energies to determine interface locations in a multilayer shield. The method was implemented with a Newton-Raphson optimization algorithm, and it worked very well in numerical one-dimensional spherical test cases. A more sophisticated optimization method would better exploit the potential of the inverse method.
The inverse square law of gravitation
International Nuclear Information System (INIS)
Cook, A.H.
1987-01-01
The inverse square law of gravitation is very well established over the distances of celestial mechanics, while in electrostatics the law has been shown to be followed to very high precision. However, it is only within the last century that any laboratory experiments have been made to test the inverse square law for gravitation, and all but one has been carried out in the last ten years. At the same time, there has been considerable interest in the possibility of deviations from the inverse square law, either because of a possible bearing on unified theories of forces, including gravitation or, most recently, because of a possible additional fifth force of nature. In this article the various lines of evidence for the inverse square law are summarized, with emphasis upon the recent laboratory experiments. (author)
Photo-induced persistent inversion of germanium in a 200-nm-deep surface region.
Prokscha, T; Chow, K H; Stilp, E; Suter, A; Luetkens, H; Morenzoni, E; Nieuwenhuys, G J; Salman, Z; Scheuermann, R
2013-01-01
The controlled manipulation of the charge carrier concentration in nanometer thin layers is the basis of current semiconductor technology and of fundamental importance for device applications. Here we show that it is possible to induce a persistent inversion from n- to p-type in a 200-nm-thick surface layer of a germanium wafer by illumination with white and blue light. We induce the inversion with a half-life of ~12 hours at a temperature of 220 K which disappears above 280 K. The photo-induced inversion is absent for a sample with a 20-nm-thick gold capping layer providing a Schottky barrier at the interface. This indicates that charge accumulation at the surface is essential to explain the observed inversion. The contactless change of carrier concentration is potentially interesting for device applications in opto-electronics where the gate electrode and gate oxide could be replaced by the semiconductor surface.
Bayesian inversion of refraction seismic traveltime data
Ryberg, T.; Haberland, Ch
2018-03-01
We apply a Bayesian Markov chain Monte Carlo (McMC) formalism to the inversion of refraction seismic, traveltime data sets to derive 2-D velocity models below linear arrays (i.e. profiles) of sources and seismic receivers. Typical refraction data sets, especially when using the far-offset observations, are known as having experimental geometries which are very poor, highly ill-posed and far from being ideal. As a consequence, the structural resolution quickly degrades with depth. Conventional inversion techniques, based on regularization, potentially suffer from the choice of appropriate inversion parameters (i.e. number and distribution of cells, starting velocity models, damping and smoothing constraints, data noise level, etc.) and only local model space exploration. McMC techniques are used for exhaustive sampling of the model space without the need of prior knowledge (or assumptions) of inversion parameters, resulting in a large number of models fitting the observations. Statistical analysis of these models allows to derive an average (reference) solution and its standard deviation, thus providing uncertainty estimates of the inversion result. The highly non-linear character of the inversion problem, mainly caused by the experiment geometry, does not allow to derive a reference solution and error map by a simply averaging procedure. We present a modified averaging technique, which excludes parts of the prior distribution in the posterior values due to poor ray coverage, thus providing reliable estimates of inversion model properties even in those parts of the models. The model is discretized by a set of Voronoi polygons (with constant slowness cells) or a triangulated mesh (with interpolation within the triangles). Forward traveltime calculations are performed by a fast, finite-difference-based eikonal solver. The method is applied to a data set from a refraction seismic survey from Northern Namibia and compared to conventional tomography. An inversion test
An Inversion Recovery NMR Kinetics Experiment
Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping
2011-01-01
A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a conveni...
Approximation of Bayesian Inverse Problems for PDEs
Cotter, S. L.; Dashti, M.; Stuart, A. M.
2010-01-01
Inverse problems are often ill posed, with solutions that depend sensitively on data.n any numerical approach to the solution of such problems, regularization of some form is needed to counteract the resulting instability. This paper is based on an approach to regularization, employing a Bayesian formulation of the problem, which leads to a notion of well posedness for inverse problems, at the level of probability measures. The stability which results from this well posedness may be used as t...
On the Inversion of the Lidar Equation
1984-11-01
sectitns briefly review the major inversion methods to date and a fourth section describes the development of the modified inversion method. All four...can be seeu when It is understood ’in terms of its ,physical significance. Equation 17 states that the normalized integrated backscatter has a limit. In...still give significant errors. 4.0 VALIDATION OF AGILE In this chapter, evidence of the success of AGILE will be reviewed and compared with Klett’s
Inverse regression for ridge recovery II: Numerics
Glaws, Andrew; Constantine, Paul G.; Cook, R. Dennis
2018-01-01
We investigate the application of sufficient dimension reduction (SDR) to a noiseless data set derived from a deterministic function of several variables. In this context, SDR provides a framework for ridge recovery. In this second part, we explore the numerical subtleties associated with using two inverse regression methods---sliced inverse regression (SIR) and sliced average variance estimation (SAVE)---for ridge recovery. This includes a detailed numerical analysis of the eigenvalues of th...
Fast nonlinear susceptibility inversion with variational regularization.
Milovic, Carlos; Bilgic, Berkin; Zhao, Bo; Acosta-Cabronero, Julio; Tejos, Cristian
2018-01-10
Quantitative susceptibility mapping can be performed through the minimization of a function consisting of data fidelity and regularization terms. For data consistency, a Gaussian-phase noise distribution is often assumed, which breaks down when the signal-to-noise ratio is low. A previously proposed alternative is to use a nonlinear data fidelity term, which reduces streaking artifacts, mitigates noise amplification, and results in more accurate susceptibility estimates. We hereby present a novel algorithm that solves the nonlinear functional while achieving computation speeds comparable to those for a linear formulation. We developed a nonlinear quantitative susceptibility mapping algorithm (fast nonlinear susceptibility inversion) based on the variable splitting and alternating direction method of multipliers, in which the problem is split into simpler subproblems with closed-form solutions and a decoupled nonlinear inversion hereby solved with a Newton-Raphson iterative procedure. Fast nonlinear susceptibility inversion performance was assessed using numerical phantom and in vivo experiments, and was compared against the nonlinear morphology-enabled dipole inversion method. Fast nonlinear susceptibility inversion achieves similar accuracy to nonlinear morphology-enabled dipole inversion but with significantly improved computational efficiency. The proposed method enables accurate reconstructions in a fraction of the time required by state-of-the-art quantitative susceptibility mapping methods. Magn Reson Med, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2018 International Society for Magnetic Resonance in Medicine.
Atmospheric inverse modeling via sparse reconstruction
Directory of Open Access Journals (Sweden)
N. Hase
2017-10-01
Full Text Available Many applications in atmospheric science involve ill-posed inverse problems. A crucial component of many inverse problems is the proper formulation of a priori knowledge about the unknown parameters. In most cases, this knowledge is expressed as a Gaussian prior. This formulation often performs well at capturing smoothed, large-scale processes but is often ill equipped to capture localized structures like large point sources or localized hot spots. Over the last decade, scientists from a diverse array of applied mathematics and engineering fields have developed sparse reconstruction techniques to identify localized structures. In this study, we present a new regularization approach for ill-posed inverse problems in atmospheric science. It is based on Tikhonov regularization with sparsity constraint and allows bounds on the parameters. We enforce sparsity using a dictionary representation system. We analyze its performance in an atmospheric inverse modeling scenario by estimating anthropogenic US methane (CH4 emissions from simulated atmospheric measurements. Different measures indicate that our sparse reconstruction approach is better able to capture large point sources or localized hot spots than other methods commonly used in atmospheric inversions. It captures the overall signal equally well but adds details on the grid scale. This feature can be of value for any inverse problem with point or spatially discrete sources. We show an example for source estimation of synthetic methane emissions from the Barnett shale formation.
Atmospheric inverse modeling via sparse reconstruction
Hase, Nils; Miller, Scot M.; Maaß, Peter; Notholt, Justus; Palm, Mathias; Warneke, Thorsten
2017-10-01
Many applications in atmospheric science involve ill-posed inverse problems. A crucial component of many inverse problems is the proper formulation of a priori knowledge about the unknown parameters. In most cases, this knowledge is expressed as a Gaussian prior. This formulation often performs well at capturing smoothed, large-scale processes but is often ill equipped to capture localized structures like large point sources or localized hot spots. Over the last decade, scientists from a diverse array of applied mathematics and engineering fields have developed sparse reconstruction techniques to identify localized structures. In this study, we present a new regularization approach for ill-posed inverse problems in atmospheric science. It is based on Tikhonov regularization with sparsity constraint and allows bounds on the parameters. We enforce sparsity using a dictionary representation system. We analyze its performance in an atmospheric inverse modeling scenario by estimating anthropogenic US methane (CH4) emissions from simulated atmospheric measurements. Different measures indicate that our sparse reconstruction approach is better able to capture large point sources or localized hot spots than other methods commonly used in atmospheric inversions. It captures the overall signal equally well but adds details on the grid scale. This feature can be of value for any inverse problem with point or spatially discrete sources. We show an example for source estimation of synthetic methane emissions from the Barnett shale formation.
An application of sparse inversion on the calculation of the inverse data space of geophysical data
Saragiotis, Christos
2011-07-01
Multiple reflections as observed in seismic reflection measurements often hide arrivals from the deeper target reflectors and need to be removed. The inverse data space provides a natural separation of primaries and surface-related multiples, as the surface multiples map onto the area around the origin while the primaries map elsewhere. However, the calculation of the inverse data is far from trivial as theory requires infinite time and offset recording. Furthermore regularization issues arise during inversion. We perform the inversion by minimizing the least-squares norm of the misfit function and by constraining the 1 norm of the solution, being the inverse data space. In this way a sparse inversion approach is obtained. We show results on field data with an application to surface multiple removal. © 2011 IEEE.
International Nuclear Information System (INIS)
Zhang, F.Z.; Jiang, P.X.; Lin, Y.S.; Zhang, Y.W.
2011-01-01
An internal heat exchanger (IHX) is often used to improve the coefficient of performance (COP) of CO 2 inverse cycles. This paper presents a detailed analysis of the IHX's effect in CO 2 inverse cycles and finds suitable operating conditions for the IHX from a thermodynamic performance point of view. The results indicate that the COP is slightly reduced by an IHX in a CO 2 subcritical inverse cycle, so an IHX is not justified. However, for transcritical CO 2 inverse cycles, the compressor discharge pressures and CO 2 gas cooler outlet temperatures both have significant impacts on system performance. The analysis results for transcritical CO 2 inverse cycles show that a transition discharge pressure and a transition CO 2 gas cooler outlet temperature are objective existence above which the IHX improves the cycle performance. - Research highlights: → Find suitable operating conditions for the IHX. → Above transition CO2 gas cooler outlet temperature IHX improves cycle performance. → The IHX is not very useful for optimized space heating and refrigerating cycles.
Chromatid Painting for Chromosomal Inversion Detection, Phase I
National Aeronautics and Space Administration — We propose a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and inversions) have profound genetic...
Inverse Supersymmetry Breaking in S1 × R3
Directory of Open Access Journals (Sweden)
Vasilis Oikonomou
2010-03-01
Full Text Available In this paper, we study the influence of hard supersymmetry breaking terms in a N = 1, d = 4 supersymmetric model, in S1 × R3 spacetime topology. It is shown that when the radius of the compact dimension is large supersymmetry is unbroken, and dynamically breaks as the radius decreases. We point out that this resembles the inverse symmetry breaking of continuous symmetries at finite temperature (however, in the case of supersymmetry, the role of the temperature is played by the compact dimension’s radius. Furthermore, we also find a universality in the dependence of the critical length Lc as a function of a coupling g3, after comparing all cases.
Reconstructing the Hopfield network as an inverse Ising problem
International Nuclear Information System (INIS)
Huang Haiping
2010-01-01
We test four fast mean-field-type algorithms on Hopfield networks as an inverse Ising problem. The equilibrium behavior of Hopfield networks is simulated through Glauber dynamics. In the low-temperature regime, the simulated annealing technique is adopted. Although performances of these network reconstruction algorithms on the simulated network of spiking neurons are extensively studied recently, the analysis of Hopfield networks is lacking so far. For the Hopfield network, we found that, in the retrieval phase favored when the network wants to memory one of stored patterns, all the reconstruction algorithms fail to extract interactions within a desired accuracy, and the same failure occurs in the spin-glass phase where spurious minima show up, while in the paramagnetic phase, albeit unfavored during the retrieval dynamics, the algorithms work well to reconstruct the network itself. This implies that, as an inverse problem, the paramagnetic phase is conversely useful for reconstructing the network while the retrieval phase loses all the information about interactions in the network except for the case where only one pattern is stored. The performances of algorithms are studied with respect to the system size, memory load, and temperature; sample-to-sample fluctuations are also considered.
Inverse Compton X-ray signature of AGN feedback
Bourne, Martin A.; Nayakshin, Sergei
2013-12-01
Bright AGN frequently show ultrafast outflows (UFOs) with outflow velocities vout ˜ 0.1c. These outflows may be the source of AGN feedback on their host galaxies sought by galaxy formation modellers. The exact effect of the outflows on the ambient galaxy gas strongly depends on whether the shocked UFOs cool rapidly or not. This in turn depends on whether the shocked electrons share the same temperature as ions (one-temperature regime, 1T) or decouple (2T), as has been recently suggested. Here we calculate the inverse Compton spectrum emitted by such shocks, finding a broad feature potentially detectable either in mid-to-high energy X-rays (1T case) or only in the soft X-rays (2T). We argue that current observations of AGN do not seem to show evidence for the 1T component. The limits on the 2T emission are far weaker, and in fact it is possible that the observed soft X-ray excess of AGN is partially or fully due to the 2T shock emission. This suggests that UFOs are in the energy-driven regime outside the central few pc, and must pump considerable amounts of not only momentum but also energy into the ambient gas. We encourage X-ray observers to look for the inverse Compton components calculated here in order to constrain AGN feedback models further.
Reconstructing the Hopfield network as an inverse Ising problem
Huang, Haiping
2010-03-01
We test four fast mean-field-type algorithms on Hopfield networks as an inverse Ising problem. The equilibrium behavior of Hopfield networks is simulated through Glauber dynamics. In the low-temperature regime, the simulated annealing technique is adopted. Although performances of these network reconstruction algorithms on the simulated network of spiking neurons are extensively studied recently, the analysis of Hopfield networks is lacking so far. For the Hopfield network, we found that, in the retrieval phase favored when the network wants to memory one of stored patterns, all the reconstruction algorithms fail to extract interactions within a desired accuracy, and the same failure occurs in the spin-glass phase where spurious minima show up, while in the paramagnetic phase, albeit unfavored during the retrieval dynamics, the algorithms work well to reconstruct the network itself. This implies that, as an inverse problem, the paramagnetic phase is conversely useful for reconstructing the network while the retrieval phase loses all the information about interactions in the network except for the case where only one pattern is stored. The performances of algorithms are studied with respect to the system size, memory load, and temperature; sample-to-sample fluctuations are also considered.
Inverse modeling for heat conduction problem in human abdominal phantom.
Huang, Ming; Chen, Wenxi
2011-01-01
Noninvasive methods for deep body temperature measurement are based on the principle of heat equilibrium between the thermal sensor and the target location theoretically. However, the measurement position is not able to be definitely determined. In this study, a 2-dimensional mathematical model was built based upon some assumptions for the physiological condition of the human abdomen phantom. We evaluated the feasibility in estimating the internal organs temperature distribution from the readings of the temperature sensors arranged on the skin surface. It is a typical inverse heat conduction problem (IHCP), and is usually mathematically ill-posed. In this study, by integrating some physical and physiological a-priori information, we invoked the quasi-linear (QL) method to reconstruct the internal temperature distribution. The solutions of this method were improved by increasing the accuracy of the sensors and adjusting their arrangement on the outer surface, and eventually reached the state of converging at the best state accurately. This study suggests that QL method is able to reconstruct the internal temperature distribution in this phantom and might be worthy of a further study in an anatomical based model.
QCD-instantons and conformal inversion symmetry
International Nuclear Information System (INIS)
Klammer, D.
2006-07-01
Instantons are an essential and non-perturbative part of Quantum Chromodynamics, the theory of strong interactions. One of the most relevant quantities in the instanton calculus is the instanton-size distribution, which can be described on the one hand within the framework of instanton perturbation theory and on the other hand investigated numerically by means of lattice computations. A rapid onset of a drastic discrepancy between these respective results indicates that the underlying physics is not yet well understood. In this work we investigate the appealing possibility of a symmetry under conformal inversion of space-time leading to this deviation. The motivation being that the lattice data seem to be invariant under an inversion of the instanton size. Since the instanton solution of a given size turns into an anti-instanton solution having an inverted size under conformal inversion of space-time, we ask in a first investigation, whether this property is transferred to the quantum level. In order to introduce a new scale, which is indicated by the lattice data and corresponds to the average instanton size as inversion radius, we project the instanton calculus onto the four-dimensional surface of a five-dimensional sphere via stereographic projection. The radius of this sphere is associated with the average instanton size. The result for the instanton size-distribution projected onto the sphere agrees surprisingly well with the lattice data at qualitative level. The resulting symmetry under an inversion of the instanton size is almost perfect. (orig.)
QCD-instantons and conformal inversion symmetry
Energy Technology Data Exchange (ETDEWEB)
Klammer, D.
2006-07-15
Instantons are an essential and non-perturbative part of Quantum Chromodynamics, the theory of strong interactions. One of the most relevant quantities in the instanton calculus is the instanton-size distribution, which can be described on the one hand within the framework of instanton perturbation theory and on the other hand investigated numerically by means of lattice computations. A rapid onset of a drastic discrepancy between these respective results indicates that the underlying physics is not yet well understood. In this work we investigate the appealing possibility of a symmetry under conformal inversion of space-time leading to this deviation. The motivation being that the lattice data seem to be invariant under an inversion of the instanton size. Since the instanton solution of a given size turns into an anti-instanton solution having an inverted size under conformal inversion of space-time, we ask in a first investigation, whether this property is transferred to the quantum level. In order to introduce a new scale, which is indicated by the lattice data and corresponds to the average instanton size as inversion radius, we project the instanton calculus onto the four-dimensional surface of a five-dimensional sphere via stereographic projection. The radius of this sphere is associated with the average instanton size. The result for the instanton size-distribution projected onto the sphere agrees surprisingly well with the lattice data at qualitative level. The resulting symmetry under an inversion of the instanton size is almost perfect. (orig.)
Unwrapped phase inversion with an exponential damping
Choi, Yun Seok
2015-07-28
Full-waveform inversion (FWI) suffers from the phase wrapping (cycle skipping) problem when the frequency of data is not low enough. Unless we obtain a good initial velocity model, the phase wrapping problem in FWI causes a result corresponding to a local minimum, usually far away from the true solution, especially at depth. Thus, we have developed an inversion algorithm based on a space-domain unwrapped phase, and we also used exponential damping to mitigate the nonlinearity associated with the reflections. We construct the 2D phase residual map, which usually contains the wrapping discontinuities, especially if the model is complex and the frequency is high. We then unwrap the phase map and remove these cycle-based jumps. However, if the phase map has several residues, the unwrapping process becomes very complicated. We apply a strong exponential damping to the wavefield to eliminate much of the residues in the phase map, thus making the unwrapping process simple. We finally invert the unwrapped phases using the back-propagation algorithm to calculate the gradient. We progressively reduce the damping factor to obtain a high-resolution image. Numerical examples determined that the unwrapped phase inversion with a strong exponential damping generated convergent long-wavelength updates without low-frequency information. This model can be used as a good starting model for a subsequent inversion with a reduced damping, eventually leading to conventional waveform inversion.
RUMBLE Technical Report on Inversion Models
Simons, Dick G.; Ainslie, Michael A.; Muller, Simonette H. E.; Boek, Wilco
2002-06-01
The performance of long range low frequency active sonar (LFAS) systems in shallow water is very sensitive to the properties of the sea bed, because of the impact of these on propagation, reverberation and (to a lesser extent) ambient noise. Direct measurement of sea bed parameters using cores or grab samples is impractical for covering a wide area, and instead we consider the possibility of using the LFAS system itself to measure its operating environment. The advantages of this approach are that it exploits existing (or planned) equipment and potentially offers a wide coverage. Geo-acoustic inversion methods are reviewed, with particular consideration for the problems associated with inversion of reverberation data. Three global optimisation methods are described, known as "simulated annealing", "genetic algorithms" and "differential evolution". The Levenberg-Marquardt and downhill simplex local methods are also described. The advantages and disadvantages of each individual method, as well as some hybrid combinations, are discussed in the context of geo-acoustic inversion. A new inversion method has been developed that exploits both the shape and height of the reverberation vs time curve to obtain information about the sea bed reflection loss and scattering strength separately. Tests on synthetic reverberation data show that the inversion method is able to extract parameters representing reflection loss and scattering strength, but cannot always unambiguously separate the effects of sediment sound speed and attenuation. The method is robust to small mismatches in water depth, sonar depth, sediment sound speed gradient and wind speed.
Full wave-field reflection coefficient inversion.
Dettmer, Jan; Dosso, Stan E; Holland, Charles W
2007-12-01
This paper develops a Bayesian inversion for recovering multilayer geoacoustic (velocity, density, attenuation) profiles from a full wave-field (spherical-wave) seabed reflection response. The reflection data originate from acoustic time series windowed for a single bottom interaction, which are processed to yield reflection coefficient data as a function of frequency and angle. Replica data for inversion are computed using a wave number-integration model to calculate the full complex acoustic pressure field, which is processed to produce a commensurate seabed response function. To address the high computational cost of calculating short range acoustic fields, the inversion algorithms are parallelized and frequency averaging is replaced by range averaging in the forward model. The posterior probability density is interpreted in terms of optimal parameter estimates, marginal distributions, and credibility intervals. Inversion results for the full wave-field seabed response are compared to those obtained using plane-wave reflection coefficients. A realistic synthetic study indicates that the plane-wave assumption can fail, producing erroneous results with misleading uncertainty bounds, whereas excellent results are obtained with the full-wave reflection inversion.
Multiscattering inversion for low-model wavenumbers
Alkhalifah, Tariq Ali
2016-09-21
A successful full-waveform inversion implementation updates the low-wavenumber model components first for a proper description of the wavefield propagation and slowly adds the high wavenumber potentially scattering parts of the model. The low-wavenumber components can be extracted from the transmission parts of the recorded wavefield emanating directly from the source or the transmission parts from the single- or double-scattered wavefield computed from a predicted scatter field acting as secondary sources.We use a combined inversion of data modeled from the source and those corresponding to single and double scattering to update the velocity model and the component of the velocity (perturbation) responsible for the single and double scattering. The combined inversion helps us access most of the potential model wavenumber information that may be embedded in the data. A scattering-angle filter is used to divide the gradient of the combined inversion, so initially the high-wavenumber (low-scattering-angle) components of the gradient are directed to the perturbation model and the low-wavenumber (highscattering- angle) components are directed to the velocity model. As our background velocity matures, the scatteringangle divide is slowly lowered to allow for more of the higher wavenumbers to contribute the velocity model. Synthetic examples including the Marmousi model are used to demonstrate the additional illumination and improved velocity inversion obtained when including multiscattered energy. © 2016 Society of Exploration Geophysicists.
Alternating minimisation for glottal inverse filtering
Rodrigo Bleyer, Ismael; Lybeck, Lasse; Auvinen, Harri; Airaksinen, Manu; Alku, Paavo; Siltanen, Samuli
2017-06-01
A new method is proposed for solving the glottal inverse filtering (GIF) problem. The goal of GIF is to separate an acoustical speech signal into two parts: the glottal airflow excitation and the vocal tract filter. To recover such information one has to deal with a blind deconvolution problem. This ill-posed inverse problem is solved under a deterministic setting, considering unknowns on both sides of the underlying operator equation. A stable reconstruction is obtained using a double regularization strategy, alternating between fixing either the glottal source signal or the vocal tract filter. This enables not only splitting the nonlinear and nonconvex problem into two linear and convex problems, but also allows the use of the best parameters and constraints to recover each variable at a time. This new technique, called alternating minimization glottal inverse filtering (AM-GIF), is compared with two other approaches: Markov chain Monte Carlo glottal inverse filtering (MCMC-GIF), and iterative adaptive inverse filtering (IAIF), using synthetic speech signals. The recent MCMC-GIF has good reconstruction quality but high computational cost. The state-of-the-art IAIF method is computationally fast but its accuracy deteriorates, particularly for speech signals of high fundamental frequency (F0). The results show the competitive performance of the new method: With high F0, the reconstruction quality is better than that of IAIF and close to MCMC-GIF while reducing the computational complexity by two orders of magnitude.
Speaker independent acoustic-to-articulatory inversion
Ji, An
Acoustic-to-articulatory inversion, the determination of articulatory parameters from acoustic signals, is a difficult but important problem for many speech processing applications, such as automatic speech recognition (ASR) and computer aided pronunciation training (CAPT). In recent years, several approaches have been successfully implemented for speaker dependent models with parallel acoustic and kinematic training data. However, in many practical applications inversion is needed for new speakers for whom no articulatory data is available. In order to address this problem, this dissertation introduces a novel speaker adaptation approach called Parallel Reference Speaker Weighting (PRSW), based on parallel acoustic and articulatory Hidden Markov Models (HMM). This approach uses a robust normalized articulatory space and palate referenced articulatory features combined with speaker-weighted adaptation to form an inversion mapping for new speakers that can accurately estimate articulatory trajectories. The proposed PRSW method is evaluated on the newly collected Marquette electromagnetic articulography -- Mandarin Accented English (EMA-MAE) corpus using 20 native English speakers. Cross-speaker inversion results show that given a good selection of reference speakers with consistent acoustic and articulatory patterns, the PRSW approach gives good speaker independent inversion performance even without kinematic training data.
Machine Learning and Inverse Problem in Geodynamics
Shahnas, M. H.; Yuen, D. A.; Pysklywec, R.
2017-12-01
During the past few decades numerical modeling and traditional HPC have been widely deployed in many diverse fields for problem solutions. However, in recent years the rapid emergence of machine learning (ML), a subfield of the artificial intelligence (AI), in many fields of sciences, engineering, and finance seems to mark a turning point in the replacement of traditional modeling procedures with artificial intelligence-based techniques. The study of the circulation in the interior of Earth relies on the study of high pressure mineral physics, geochemistry, and petrology where the number of the mantle parameters is large and the thermoelastic parameters are highly pressure- and temperature-dependent. More complexity arises from the fact that many of these parameters that are incorporated in the numerical models as input parameters are not yet well established. In such complex systems the application of machine learning algorithms can play a valuable role. Our focus in this study is the application of supervised machine learning (SML) algorithms in predicting mantle properties with the emphasis on SML techniques in solving the inverse problem. As a sample problem we focus on the spin transition in ferropericlase and perovskite that may cause slab and plume stagnation at mid-mantle depths. The degree of the stagnation depends on the degree of negative density anomaly at the spin transition zone. The training and testing samples for the machine learning models are produced by the numerical convection models with known magnitudes of density anomaly (as the class labels of the samples). The volume fractions of the stagnated slabs and plumes which can be considered as measures for the degree of stagnation are assigned as sample features. The machine learning models can determine the magnitude of the spin transition-induced density anomalies that can cause flow stagnation at mid-mantle depths. Employing support vector machine (SVM) algorithms we show that SML techniques
Cai, W.D.; Ramesh, N.; Tihminlioglu, F.; Danner, R.P.; Duda, J.L.; de Haan, A.B.
2002-01-01
The capillary-column inverse gas chromatography method was used to measure the diffusion and partition coefficients of ethylbenzene, styrene, and acrylonitrile in polybutadiene (PBD) at infinite dilution of the solvents. Experiments were performed over a temperature range of 50-125 °C. At
Oil core microcapsules by inverse gelation technique.
Martins, Evandro; Renard, Denis; Davy, Joëlle; Marquis, Mélanie; Poncelet, Denis
2015-01-01
A promising technique for oil encapsulation in Ca-alginate capsules by inverse gelation was proposed by Abang et al. This method consists of emulsifying calcium chloride solution in oil and then adding it dropwise in an alginate solution to produce Ca-alginate capsules. Spherical capsules with diameters around 3 mm were produced by this technique, however the production of smaller capsules was not demonstrated. The objective of this study is to propose a new method of oil encapsulation in a Ca-alginate membrane by inverse gelation. The optimisation of the method leads to microcapsules with diameters around 500 μm. In a search of microcapsules with improved diffusion characteristics, the size reduction is an essential factor to broaden the applications in food, cosmetics and pharmaceuticals areas. This work contributes to a better understanding of the inverse gelation technique and allows the production of microcapsules with a well-defined shell-core structure.
Fuzzy logic guided inverse treatment planning
International Nuclear Information System (INIS)
Yan Hui; Yin Fangfang; Guan Huaiqun; Kim, Jae Ho
2003-01-01
A fuzzy logic technique was applied to optimize the weighting factors in the objective function of an inverse treatment planning system for intensity-modulated radiation therapy (IMRT). Based on this technique, the optimization of weighting factors is guided by the fuzzy rules while the intensity spectrum is optimized by a fast-monotonic-descent method. The resultant fuzzy logic guided inverse planning system is capable of finding the optimal combination of weighting factors for different anatomical structures involved in treatment planning. This system was tested using one simulated (but clinically relevant) case and one clinical case. The results indicate that the optimal balance between the target dose and the critical organ dose is achieved by a refined combination of weighting factors. With the help of fuzzy inference, the efficiency and effectiveness of inverse planning for IMRT are substantially improved
Surface Vibration Reconstruction using Inverse Numerical Acoustics
Directory of Open Access Journals (Sweden)
F. Martinus
2003-05-01
Full Text Available This paper explores the use of inverse numerical acoustics to reconstruct the surface vibration of a noise source. Inverse numerical acoustics is mainly used for source identification. This approach uses the measured sound pressure at a set of field points and the Helmholtz integral equation to reconstruct the normal surface velocity. The number of sound pressure measurements is considerably less than the number of surface vibration nodes. An overview of inverse numerical acoustics is presented and compared with other holography techniques such as nearfield acoustical holography and the Helmholtz equation least squares method. In order to obtain an acceptable reproduction of the surface vibration, several critical factors such as the field point selection and the effect of experimental errors have to be handled properly. Other practical considerations such as the use of few measured velocities and regularization techniques will also be presented. Examples will include a diesel engine, a transmission housing and an engine cover.
Inverse problems in linear transport theory
International Nuclear Information System (INIS)
Dressler, K.
1988-01-01
Inverse problems for a class of linear kinetic equations are investigated. The aim is to identify the scattering kernel of a transport equation (corresponding to the structure of a background medium) by observing the 'albedo' part of the solution operator for the corresponding direct initial boundary value problem. This means to get information on some integral operator in an integrodifferential equation through on overdetermined boundary value problem. We first derive a constructive method for solving direct halfspace problems and prove a new factorization theorem for the solutions. Using this result we investigate stationary inverse problems with respect to well posedness (e.g. reduce them to classical ill-posed problems, such as integral equations of first kind). In the time-dependent case we show that a quite general inverse problem is well posed and solve it constructively. (orig.)
Applications of inverse and algebraic scattering theories
International Nuclear Information System (INIS)
Amos, K.
1997-01-01
Inverse scattering theories, algebraic scattering theory and exactly solvable scattering potentials are diverse ways by which scattering potentials can be defined from S-functions specified by fits to fixed energy, quantal scattering data. Applications have been made in nuclear (heavy ion and nucleon-nucleus scattering), atomic and molecular (electron scattering from simple molecules) systems. Three inverse scattering approaches are considered in detail; the semiclassical WKB and fully quantal Lipperheide-Fiedeldey method, than algebraic scattering theory is applied to heavy ion scattering and finally the exactly solvable Ginocchio potentials. Some nuclear results are ambiguous but the atomic and molecular inversion potentials are in good agreement with postulated forms. 21 refs., 12 figs
Probabilistic inversion for chicken processing lines
Energy Technology Data Exchange (ETDEWEB)
Cooke, Roger M. [Department of Mathematics, Delft University of Technology, Delft (Netherlands)]. E-mail: r.m.cooke@ewi.tudelft.nl; Nauta, Maarten [Microbiological Laboratory for Health Protection RIVM, Bilthoven (Netherlands); Havelaar, Arie H. [Microbiological Laboratory for Health Protection RIVM, Bilthoven (Netherlands); Fels, Ine van der [Microbiological Laboratory for Health Protection RIVM, Bilthoven (Netherlands)
2006-10-15
We discuss an application of probabilistic inversion techniques to a model of campylobacter transmission in chicken processing lines. Such techniques are indicated when we wish to quantify a model which is new and perhaps unfamiliar to the expert community. In this case there are no measurements for estimating model parameters, and experts are typically unable to give a considered judgment. In such cases, experts are asked to quantify their uncertainty regarding variables which can be predicted by the model. The experts' distributions (after combination) are then pulled back onto the parameter space of the model, a process termed 'probabilistic inversion'. This study illustrates two such techniques, iterative proportional fitting (IPF) and PARmeter fitting for uncertain models (PARFUM). In addition, we illustrate how expert judgement on predicted observable quantities in combination with probabilistic inversion may be used for model validation and/or model criticism.
Inverse osmotic process for radioactive laundry waste
International Nuclear Information System (INIS)
Ebara, Katsuya; Takahashi, Sankichi; Sugimoto, Yoshikazu; Yusa, Hideo; Hyakutake, Hiroshi.
1977-01-01
Purpose: To effectively recover the processing amount reduced in a continuous treatment. Method: Laundry waste containing radioactive substances discharged from a nuclear power plant is processed in an inverse osmotic process while adding starch digesting enzymes such as amylase and takadiastase, as well as soft spherical bodies such as sponge balls of a particle diameter capable of flowing in the flow of the liquid wastes along the inverse osmotic membrane pipe and having such a softness and roundness as not to damage the inverse osmotic membrane. This process can remove the floating materials such as thread dusts or hairs deposited on the membrane surface by the action of the soft elastic balls and remove paste or the like through decomposition by the digesting enzymes. Consequently, effective recovery can be attained for the reduced processing amount. (Furukawa, Y.)
Probabilistic inversion for chicken processing lines
International Nuclear Information System (INIS)
Cooke, Roger M.; Nauta, Maarten; Havelaar, Arie H.; Fels, Ine van der
2006-01-01
We discuss an application of probabilistic inversion techniques to a model of campylobacter transmission in chicken processing lines. Such techniques are indicated when we wish to quantify a model which is new and perhaps unfamiliar to the expert community. In this case there are no measurements for estimating model parameters, and experts are typically unable to give a considered judgment. In such cases, experts are asked to quantify their uncertainty regarding variables which can be predicted by the model. The experts' distributions (after combination) are then pulled back onto the parameter space of the model, a process termed 'probabilistic inversion'. This study illustrates two such techniques, iterative proportional fitting (IPF) and PARmeter fitting for uncertain models (PARFUM). In addition, we illustrate how expert judgement on predicted observable quantities in combination with probabilistic inversion may be used for model validation and/or model criticism
Inverse Kinematic Analysis Of A Quadruped Robot
Directory of Open Access Journals (Sweden)
Muhammed Arif Sen
2017-09-01
Full Text Available This paper presents an inverse kinematics program of a quadruped robot. The kinematics analysis is main problem in the manipulators and robots. Dynamic and kinematic structures of quadruped robots are very complex compared to industrial and wheeled robots. In this study inverse kinematics solutions for a quadruped robot with 3 degrees of freedom on each leg are presented. Denavit-Hartenberg D-H method are used for the forward kinematic. The inverse kinematic equations obtained by the geometrical and mathematical methods are coded in MATLAB. And thus a program is obtained that calculate the legs joint angles corresponding to desired various orientations of robot and endpoints of legs. Also the program provides the body orientations of robot in graphical form. The angular positions of joints obtained corresponding to desired different orientations of robot and endpoints of legs are given in this study.
Heriyanto, M.; Srigutomo, W.
2017-07-01
Exploration of natural or energy resources requires geophysical survey to determine the subsurface structure, such as DC resistivity method. In this research, field and synthetic data were used using Schlumberger configuration. One-dimensional (1-D) DC resistivity inversion was carried out using Singular Value Decomposition (SVD) and Levenberg-Marquardt (LM) techniques to obtain layered resistivity structure. We have developed software to perform both inversion methods accompanied by a user-friendly interface. Both of the methods were compared one another to determine the number of iteration, robust to noise, elapsed time of computation, and inversion results. SVD inversion generated faster process and better results than LM did. The inversion showed both of these methods were appropriate to interpret subsurface resistivity structure.
Variability in surface inversion characteristics over India in winter ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Earth System Science; Volume 120; Issue 1. Variability in surface inversion ... Decadal variations in inversion strength show weak inversion frequencies decreasing from the 1st to the 3rd decade while moderate/strong inversions occur more frequently at most stations. Frequencies of very strong ...
Trimming and procrastination as inversion techniques
Backus, George E.
1996-12-01
By examining the processes of truncating and approximating the model space (trimming it), and by committing to neither the objectivist nor the subjectivist interpretation of probability (procrastinating), we construct a formal scheme for solving linear and non-linear geophysical inverse problems. The necessary prior information about the correct model xE can be either a collection of inequalities or a probability measure describing where xE was likely to be in the model space X before the data vector y0 was measured. The results of the inversion are (1) a vector z0 that estimates some numerical properties zE of xE; (2) an estimate of the error δz = z0 - zE. As y0 is finite dimensional, so is z0, and hence in principle inversion cannot describe all of xE. The error δz is studied under successively more specialized assumptions about the inverse problem, culminating in a complete analysis of the linear inverse problem with a prior quadratic bound on xE. Our formalism appears to encompass and provide error estimates for many of the inversion schemes current in geomagnetism, and would be equally applicable in geodesy and seismology if adequate prior information were available there. As an idealized example we study the magnetic field at the core-mantle boundary, using satellite measurements of field elements at sites assumed to be almost uniformly distributed on a single spherical surface. Magnetospheric currents are neglected and the crustal field is idealized as a random process with rotationally invariant statistics. We find that an appropriate data compression diagonalizes the variance matrix of the crustal signal and permits an analytic trimming of the idealized problem.
Mesoscale inversion of carbon sources and sinks
International Nuclear Information System (INIS)
Lauvaux, T.
2008-01-01
Inverse methods at large scales are used to infer the spatial variability of carbon sources and sinks over the continents but their uncertainties remain large. Atmospheric concentrations integrate the surface flux variability but atmospheric transport models at low resolution are not able to simulate properly the local atmospheric dynamics at the measurement sites. However, the inverse estimates are more representative of the large spatial heterogeneity of the ecosystems compared to direct flux measurements. Top-down and bottom-up methods that aim at quantifying the carbon exchanges between the surface and the atmosphere correspond to different scales and are not easily comparable. During this phD, a mesoscale inverse system was developed to correct carbon fluxes at 8 km resolution. The high resolution transport model MesoNH was used to simulate accurately the variability of the atmospheric concentrations, which allowed us to reduce the uncertainty of the retrieved fluxes. All the measurements used here were observed during the intensive regional campaign CERES of May and June 2005, during which several instrumented towers measured CO 2 concentrations and fluxes in the South West of France. Airborne measurements allowed us to observe concentrations at high altitude but also CO 2 surface fluxes over large parts of the domain. First, the capacity of the inverse system to correct the CO 2 fluxes was estimated using pseudo-data experiments. The largest fraction of the concentration variability was attributed to regional surface fluxes over an area of about 300 km around the site locations depending on the meteorological conditions. Second, an ensemble of simulations allowed us to define the spatial and temporal structures of the transport errors. Finally, the inverse fluxes at 8 km resolution were compared to direct flux measurements. The inverse system has been validated in space and time and showed an improvement of the first guess fluxes from a vegetation model
Mechanical pumping at low temperature
International Nuclear Information System (INIS)
Perin, J.P.; Claudet, G.; Disdier, F.
1995-01-01
This novel concept consist of a mechanical pump able to run at low temperature (25K). Since gas density varies inversely with temperature, this pump would deliver much higher mass flow rate than at room temperature for a given size. Advantages of this concept are order of magnitude reduction in size, weight, when compared to a conventional pump scaled to perform the same mass flow rate at room temperature. This pump would be a solution to allow continuously tritium extraction and minimize the mass inventory. (orig.)
Vector continued fractions using a generalized inverse
International Nuclear Information System (INIS)
Haydock, Roger; Nex, C M M; Wexler, Geoffrey
2004-01-01
A real vector space combined with an inverse (involution) for vectors is sufficient to define a vector continued fraction whose parameters consist of vector shifts and changes of scale. The choice of sign for different components of the vector inverse permits construction of vector analogues of the Jacobi continued fraction. These vector Jacobi fractions are related to vector and scalar-valued polynomial functions of the vectors, which satisfy recurrence relations similar to those of orthogonal polynomials. The vector Jacobi fraction has strong convergence properties which are demonstrated analytically, and illustrated numerically
Direct and Inverse problems in Electrocardiography
Boulakia, M.; Fernández, M. A.; Gerbeau, J. F.; Zemzemi, N.
2008-09-01
We present numerical results related to the direct and the inverse problems in electrocardiography. The electrical activity of the heart is described by the bidomain equations. The electrocardiograms (ECGs) recorded in different points on the body surface are obtained by coupling the bidomain equation to a Laplace equation in the torso. The simulated ECGs are quite satisfactory. As regards the inverse problem, our goal is to estimate the parameters of the bidomain-torso model. Here we present some preliminary results of a parameter estimation for the torso model.
Kinetic equation solution by inverse kinetic method
International Nuclear Information System (INIS)
Salas, G.
1983-01-01
We propose a computer program (CAMU) which permits to solve the inverse kinetic equation. The CAMU code is written in HPL language for a HP 982 A microcomputer with a peripheral interface HP 9876 A ''thermal graphic printer''. The CAMU code solves the inverse kinetic equation by taking as data entry the output of the ionization chambers and integrating the equation with the help of the Simpson method. With this program we calculate the evolution of the reactivity in time for a given disturbance
Inverse statistical approach in heartbeat time series
International Nuclear Information System (INIS)
Ebadi, H; Shirazi, A H; Mani, Ali R; Jafari, G R
2011-01-01
We present an investigation on heart cycle time series, using inverse statistical analysis, a concept borrowed from studying turbulence. Using this approach, we studied the distribution of the exit times needed to achieve a predefined level of heart rate alteration. Such analysis uncovers the most likely waiting time needed to reach a certain change in the rate of heart beat. This analysis showed a significant difference between the raw data and shuffled data, when the heart rate accelerates or decelerates to a rare event. We also report that inverse statistical analysis can distinguish between the electrocardiograms taken from healthy volunteers and patients with heart failure
Molecular seismology: an inverse problem in nanobiology.
Hinow, Peter; Boczko, Erik M
2007-05-07
The density profile of an elastic fiber like DNA will change in space and time as ligands associate with it. This observation affords a new direction in single molecule studies provided that density profiles can be measured in space and time. In fact, this is precisely the objective of seismology, where the mathematics of inverse problems have been employed with success. We argue that inverse problems in elastic media can be directly applied to biophysical problems of fiber-ligand association, and demonstrate that robust algorithms exist to perform density reconstruction in the condensed phase.
The Inverse Perspective in Byzantine Painting
Directory of Open Access Journals (Sweden)
Maria Urmă
2014-11-01
Full Text Available The inverse perspective is a method of representing spatial depth used only in Byzantine painting. It is different from Renaissance perspective (a method of realistic, conventional, subjective, subject to a single point of view. The inverse perspective, with two-dimensional axonometric representations, is more complex, offering multiple possibilities of symbolization. Various theories have considered either optical-geometric aspect or artistic-cultural aspect as the main factors that generated it. But they have not led to a unified conclusion. This study highlights the common elements of these theories, bringing together the two issues and providing a philosophical-religious interpretation.
Direct and inverse scattering for viscoelastic media
International Nuclear Information System (INIS)
Ammicht, E.; Corones, J.P.; Krueger, R.J.
1987-01-01
A time domain approach to direct and inverse scattering problems for one-dimensional viscoelastic media is presented. Such media can be characterized as having a constitutive relation between stress and strain which involves the past history of the strain through a memory function, the relaxation modulus. In the approach in this article, the relaxation modulus of a material is shown to be related to the reflection properties of the material. This relation provides a constructive algorithm for direct and inverse scattering problems. A numerical implementation of this algorithm is tested on several problems involving realistic relaxation moduli
Inversion, error analysis, and validation of GPS/MET occultation data
Energy Technology Data Exchange (ETDEWEB)
Steiner, A.K.; Kirchengast, G. [Graz Univ. (Austria). Inst. fuer Meteorologie und Geophysik; Ladreiter, H.P.
1999-01-01
The global positioning system meteorology (GPS/MET) experiment was the first practical demonstration of global navigation satellite system (GNSS)-based active limb sounding employing the radio occultation technique. This method measures, as principal observable and with millimetric accuracy, the excess phase path (relative to propagation in vacuum) of GNSS-transmitted radio waves caused by refraction during passage through the Earth`s neutral atmosphere and ionosphere in limb geometry. It shows great potential utility for weather and climate system studies in providing an unique combination of global coverage, high vertical resolution and accuracy, long-term stability, and all-weather capability. We first describe our GPS/MET data processing scheme from excess phases via bending angles to the neutral atmospheric parameters refractivity, density, pressure and temperature. Special emphasis is given to ionospheric correction methodology and the inversion of bending angles to refractivities, where we introduce a matrix inversion technique (instead of the usual integral inversion). The matrix technique is shown to lead to identical results as integral inversion but is more directly extendable to inversion by optimal estimation. The quality of GPS/MET-derived profiles is analyzed with an error estimation analysis employing a Monte Carlo technique. We consider statistical errors together with systematic errors due to upper-boundary initialization of the retrieval by a priori bending angles. Perfect initialization and properly smoothed statistical errors allow for better than 1 K temperature retrieval accuracy up to the stratopause. 28 refs.
Thermal-hydraulic modeling of flow inversion in a research reactor
International Nuclear Information System (INIS)
Kazeminejad, H.
2008-01-01
The course of loss of flow accident and flow inversion in a pool type research reactor, with scram enabled under natural circulation condition is numerically investigated. The analyses were performed by a lumped parameters approach for the coupled kinetic-thermal-hydraulics, with continuous feedback due to coolant and fuel temperature effects. A modified Runge-Kutta method was adopted for a better solution to the set of stiff differential equations. Transient thermal-hydraulics during the process of flow inversion and establishment of natural circulation were considered for a 10-MW IAEA research reactor. Some important parameters such as the peak temperatures for the hot channel were obtained for both high-enriched and low enriched fuel. The model prediction is also verified through comparison with other computer code results reported in the literature for detailed simulations of loss of flow accidents (LOFA) and the agreement between the results for the peak clad temperatures and key parameters has been satisfactory. It was found that the flow inversion and subsequent establishment of natural circulation keep the peak cladding surface temperature below the saturation temperature to avoid the escalation of clad temperature to the level of onset of nucleate boiling and sub-cooled void formation to ensure the safe operation of the reactor
Anisotropic wave-equation traveltime and waveform inversion
Feng, Shihang
2016-09-06
The wave-equation traveltime and waveform inversion (WTW) methodology is developed to invert for anisotropic parameters in a vertical transverse isotropic (VTI) meidum. The simultaneous inversion of anisotropic parameters v0, ε and δ is initially performed using the wave-equation traveltime inversion (WT) method. The WT tomograms are then used as starting background models for VTI full waveform inversion. Preliminary numerical tests on synthetic data demonstrate the feasibility of this method for multi-parameter inversion.
Inverse and Ill-posed Problems Theory and Applications
Kabanikhin, S I
2011-01-01
The text demonstrates the methods for proving the existence (if et all) and finding of inverse and ill-posed problems solutions in linear algebra, integral and operator equations, integral geometry, spectral inverse problems, and inverse scattering problems. It is given comprehensive background material for linear ill-posed problems and for coefficient inverse problems for hyperbolic, parabolic, and elliptic equations. A lot of examples for inverse problems from physics, geophysics, biology, medicine, and other areas of application of mathematics are included.
Inverse Kinematics with Closed Form Solution for Denso Robot Manipulator
Prasetia, Ikhsan Eka; Agustinah, Trihastuti
2015-01-01
In this paper, the forward kinematics and inverse kinematics used on the Denso robot manipulator which has a 6-DOF. The forward kinematics will result in the desired position by end-effector, while inverse kinematics produce angel on each joint. Inverse kinematics problem are very difficult, therefor to obtain the solution of inverse kinematics using closed form solution with geometry approach. The simulation result obtained from forward kinematics and inverse kinematics is determining desire...
Introduction to inverse problems for differential equations
Hasanov Hasanoğlu, Alemdar
2017-01-01
This book presents a systematic exposition of the main ideas and methods in treating inverse problems for PDEs arising in basic mathematical models, though it makes no claim to being exhaustive. Mathematical models of most physical phenomena are governed by initial and boundary value problems for PDEs, and inverse problems governed by these equations arise naturally in nearly all branches of science and engineering. The book’s content, especially in the Introduction and Part I, is self-contained and is intended to also be accessible for beginning graduate students, whose mathematical background includes only basic courses in advanced calculus, PDEs and functional analysis. Further, the book can be used as the backbone for a lecture course on inverse and ill-posed problems for partial differential equations. In turn, the second part of the book consists of six nearly-independent chapters. The choice of these chapters was motivated by the fact that the inverse coefficient and source problems considered here a...
Seismic Waveform Inversion by Stochastic Optimization
Directory of Open Access Journals (Sweden)
Tristan van Leeuwen
2011-01-01
Full Text Available We explore the use of stochastic optimization methods for seismic waveform inversion. The basic principle of such methods is to randomly draw a batch of realizations of a given misfit function and goes back to the 1950s. The ultimate goal of such an approach is to dramatically reduce the computational cost involved in evaluating the misfit. Following earlier work, we introduce the stochasticity in waveform inversion problem in a rigorous way via a technique called randomized trace estimation. We then review theoretical results that underlie recent developments in the use of stochastic methods for waveform inversion. We present numerical experiments to illustrate the behavior of different types of stochastic optimization methods and investigate the sensitivity to the batch size and the noise level in the data. We find that it is possible to reproduce results that are qualitatively similar to the solution of the full problem with modest batch sizes, even on noisy data. Each iteration of the corresponding stochastic methods requires an order of magnitude fewer PDE solves than a comparable deterministic method applied to the full problem, which may lead to an order of magnitude speedup for waveform inversion in practice.
Modelling and inversion of local magnetic anomalies
International Nuclear Information System (INIS)
Quesnel, Y; Langlais, B; Sotin, C; Galdéano, A
2008-01-01
We present a method—named as MILMA for modelling and inversion of local magnetic anomalies—that combines forward and inverse modelling of aeromagnetic data to characterize both magnetization properties and location of unconstrained local sources. Parameters of simple-shape magnetized bodies (cylinder, prism or sphere) are first adjusted by trial and error to predict the signal. Their parameters provide a priori information for inversion of the measurements. Here, a generalized nonlinear approach with a least-squares criterion is adopted to seek the best parameters of the sphere (dipole). This inversion step allows the model to be more objectively adjusted to fit the magnetic signal. The validity of the MILMA method is demonstrated through synthetic and real cases using aeromagnetic measurements. Tests with synthetic data reveal accurate results in terms of depth source, whatever be the number of sources. The MILMA method is then used with real measurements to constrain the properties of the magnetized units of the Champtoceaux complex (France). The resulting parameters correlate with the crustal structure and properties revealed by other geological and geophysical surveys in the same area. The MILMA method can therefore be used to investigate the properties of poorly constrained lithospheric magnetized sources
Uterine inversion complicating traditional termination of pregnancy ...
African Journals Online (AJOL)
Abortion services remain cladenstine and unsafe in most parts of Africa. This is a case of a mid-trimester abortion induced by traditional methods which resulted in uterine inversion, a previously unreported complication of induced abortion. Until abortion services are accessible and safe on the continent, morbidity and ...
Homogeneity of common cosmopolitan inversion frequencies in ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Genetics; Volume 84; Issue 2 ... Research Article Volume 84 Issue 2 August 2005 pp 173-178 ... To understand the genetic properties of Asian D. melanogaster populations, we initiated a population genetic study of chromosome inversion polymorphisms in hitherto unanalysed population ...
Improving Variational Autoencoders with Inverse Autoregressive Flow
Kingma, D.; Salimans, T.; Josefowicz, R.; Chen, X.; Sutskever, I.; Welling, M.; Lee, D.D.; von Luxburg, U.; Garnett, R.; Sugiyama, M.; Guyon, I.
2017-01-01
The framework of normalizing flows provides a general strategy for flexible variational inference of posteriors over latent variables. We propose a new type of normalizing flow, inverse autoregressive flow (IAF), that, in contrast to earlier published flows, scales well to high-dimensional latent
ILIGRA : An Efficient Inverse Line Graph Algorithm
Liu, D.; Trajanovski, S.; Van Mieghem, P.
2014-01-01
This paper presents a new and efficient algorithm, ILIGRA, for inverse line graph construction. Given a line graph H, ILIGRA constructs its root graph G with the time complexity being linear in the number of nodes in H. If ILIGRA does not know whether the given graph H is a line graph, it firstly
Solving Direct and Inverse Heat Conduction Problems
Taler, Jan
2006-01-01
Presents a solution for direct and inverse heat conduction problems. This work discusses the theoretical basis for the heat transfer process in the first part. It presents selected theoretical and numerical problems in the form of exercises with their subsequent solutions in the second part
Inverse scattering with supersymmetric quantum mechanics
International Nuclear Information System (INIS)
Baye, Daniel; Sparenberg, Jean-Marc
2004-01-01
The application of supersymmetric quantum mechanics to the inverse scattering problem is reviewed. The main difference with standard treatments of the inverse problem lies in the simple and natural extension to potentials with singularities at the origin and with a Coulomb behaviour at infinity. The most general form of potentials which are phase-equivalent to a given potential is discussed. The use of singular potentials allows adding or removing states from the bound spectrum without contradicting the Levinson theorem. Physical applications of phase-equivalent potentials in nuclear reactions and in three-body systems are described. Derivation of a potential from the phase shift at fixed orbital momentum can also be performed with the supersymmetric inversion by using a Bargmann-type approximation of the scattering matrix or phase shift. A unique singular potential without bound states can be obtained from any phase shift. A limited number of bound states depending on the singularity can then be added. This inversion procedure is illustrated with nucleon-nucleon scattering
Seismic processing in the inverse data space
Berkhout, A.J.
2006-01-01
Until now, seismic processing has been carried out by applying inverse filters in the forward data space. Because the acquired data of a seismic survey is always discrete, seismic measurements in the forward data space can be arranged conveniently in a data matrix (P). Each column in the data matrix
Inverse Problem for a Curved Quantum Guide
Directory of Open Access Journals (Sweden)
Laure Cardoulis
2012-01-01
Full Text Available We consider the Dirichlet Laplacian operator −Δ on a curved quantum guide in ℝ n(n=2,3 with an asymptotically straight reference curve. We give uniqueness results for the inverse problem associated to the reconstruction of the curvature by using either observations of spectral data or a boot-strapping method.
Neural Network Learning as an Inverse Problem
Czech Academy of Sciences Publication Activity Database
Kůrková, Věra
2005-01-01
Roč. 13, č. 5 (2005), s. 551-559 ISSN 1367-0751 R&D Projects: GA AV ČR 1ET100300517 Institutional research plan: CEZ:AV0Z10300504 Keywords : learning from data * generalization * empirical error functional * inverse problem * evaluation operator * kernel methods Subject RIV: BA - General Mathematics Impact factor: 0.382, year: 2005
Nonlinear approximation with dictionaries. II. Inverse Estimates
DEFF Research Database (Denmark)
Gribonval, Rémi; Nielsen, Morten
2006-01-01
In this paper, which is the sequel to [16], we study inverse estimates of the Bernstein type for nonlinear approximation with structured redundant dictionaries in a Banach space. The main results are for blockwise incoherent dictionaries in Hilbert spaces, which generalize the notion of joint block...
Nonlinear approximation with dictionaries,.. II: Inverse estimates
DEFF Research Database (Denmark)
Gribonval, Rémi; Nielsen, Morten
In this paper we study inverse estimates of the Bernstein type for nonlinear approximation with structured redundant dictionaries in a Banach space. The main results are for separated decomposable dictionaries in Hilbert spaces, which generalize the notion of joint block-diagonal mutually...
Inverse acoustic problem of N homogeneous scatterers
DEFF Research Database (Denmark)
Berntsen, Svend
2002-01-01
The three-dimensional inverse acoustic medium problem of N homogeneous objects with known geometry and location is considered. It is proven that one scattering experiment is sufficient for the unique determination of the complex wavenumbers of the objects. The mapping from the scattered fields...
Probabilistic Geoacoustic Inversion in Complex Environments
2015-09-30
to capture seabed variability and uncertainties consistent with data resolution, and (2) improved numerical methods for parameter and uncertainty...advancing Bayesian inference applications. • Dettmer’s work at Australian National University in seismology is closely related to some of the methods ...long-range inversion methods can fail to provide sufficient resolution. For proper quantitative examination of variability, parameter uncertainty must
Multiscale Phase Inversion of Seismic Data
Fu, Lei
2017-12-02
We present a scheme for multiscale phase inversion (MPI) of seismic data that is less sensitive to the unmodeled physics of wave propagation and a poor starting model than standard full waveform inversion (FWI). To avoid cycle-skipping, the multiscale strategy temporally integrates the traces several times, i.e. high-order integration, to produce low-boost seismograms that are used as input data for the initial iterations of MPI. As the iterations proceed, higher frequencies in the data are boosted by using integrated traces of lower order as the input data. The input data are also filtered into different narrow frequency bands for the MPI implementation. At low frequencies, we show that MPI with windowed reflections approximates wave equation inversion of the reflection traveltimes, except no traveltime picking is needed. Numerical results with synthetic acoustic data show that MPI is more robust than conventional multiscale FWI when the initial model is far from the true model. Results from synthetic viscoacoustic and elastic data show that MPI is less sensitive than FWI to some of the unmodeled physics. Inversion of marine data shows that MPI is more robust and produces modestly more accurate results than FWI for this data set.
Tectonic inversion in the Wandel Sea Basin
DEFF Research Database (Denmark)
Svennevig, Kristian; Guarnieri, Pierpaolo; Stemmerik, Lars
2016-01-01
Sheet and an upper Hondal Elv Thrust Sheet separated by a subhorizontal fault: the Central Detachment. The style of deformation and the structures described are interpreted as the result of Paleocene-Eocene N-S directed compression resulting in basin inversion with strike-slip faults only having minor...
n-Colour self-inverse compositions
Indian Academy of Sciences (India)
functions and a summation formula are obtained. Two new binomial identities with combinatorial meaning are also given. Keywords. Compositions; n-colour compositions; self-inverse compositions; seq- uences; recurrence formulas; generating functions; binomial identities. 1. Introduction. In the classical theory of partitions, ...
Inverse problem in neutron transport and radiation
International Nuclear Information System (INIS)
Barichello, L.B.; Vilhena, M.T. de
1993-01-01
In this work the LTS N method is applied to solve a inverse problem which consists on the determination of the incident angular fluxes at the boundary from the known values of the scalar flux at interior points. Numerical simulations are presented. (author)
Swarm Level 2 Comprehensive Inversion, 2016 Production
DEFF Research Database (Denmark)
Tøffner-Clausen, Lars; Sabaka, Terence; Olsen, Nils
In the framework of the ESA Earth Observation Magnetic Mapping Mission Swarm, the Expert Support Laboratories (ESL) provides high quality Level 2 Products describing a.o. the magnetic fields of the Earth. This poster provides details of the Level 2 Products from the Comprehensive Inversion chain...
Modeling and Inversion of Scattered Surface waves
Riyanti, C.D.
2005-01-01
In this thesis, we present a modeling method based on a domain-type integral representation for waves propagating along the surface of the Earth which have been scattered in the vicinity of the source or the receivers. Using this model as starting point, we formulate an inversion scheme to estimate
Semi-Inversion of Functional Parameters
DEFF Research Database (Denmark)
Mogensen, Torben Ægidius
2008-01-01
Semi-invertering er en generalisering af invertering: Et programs semi-inverse tager nogle af dets inddata og nogen af dets uddata og returnerer de resterende ind- og uddata. Tidligere arbejder har beskrevet semi-invertering af et førsteordens funktionssprog. Vi udvider nu med funktionelle...
Normalized impedance function and the straightforward inversion ...
Indian Academy of Sciences (India)
The linear straightforward inversion scheme (SIS),developed by the authors employing the concept of equal penetration layers,has been used to validate the proposed apparent resistivity functions.For this purpose,several ... Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee, UA 247 667, India.
Air-induced inverse Chladni patterns
van Gerner, H.J.; van der Weele, J.P.; van der Hoef, Martin Anton; van der Meer, Roger M.
2011-01-01
When very light particles are sprinkled on a resonating horizontal plate, inverse Chladni patterns are formed. Instead of going to the nodal lines of the plate, where they would form a standard Chladni pattern, the particles are dragged to the antinodes by the air currents induced by the vibration
Homogeneity of common cosmopolitan inversion frequencies in ...
Indian Academy of Sciences (India)
Unknown
2Present address: Population Genomics and Evolution Laboratory, Department of Biology,. Poornaprajna Institute of Scientific Research, ... climatic variables, suggesting that natural selection is operating on inversions (Krimbas and .... ses of other genetic markers (preferably at the molecular level). However, although our ...
Rapid probabilistic source inversion using pattern recognition
Käufl, Paul J.
2015-01-01
Numerous problems in the field of seismology require the determination of parameters of a physical model that are compatible with a set of observations and prior assumptions. This type of problem is generally termed inverse problem. While, in many cases, we are able to predict observations, given a
Inversion of e-simple Block Matrices
Czech Academy of Sciences Publication Activity Database
Fiedler, Miroslav
2005-01-01
Roč. 400, - (2005), s. 231-241 ISSN 0024-3795 R&D Projects: GA AV ČR IAA1030302 Institutional research plan: CEZ:AV0Z10300504 Keywords : matrix inversion * M-matrix * unipathic graph * e-simple graph Subject RIV: BA - General Mathematics Impact factor: 0.590, year: 2005
Frnakenstein: multiple target inverse RNA folding
Directory of Open Access Journals (Sweden)
Lyngsø Rune B
2012-10-01
Full Text Available Abstract Background RNA secondary structure prediction, or folding, is a classic problem in bioinformatics: given a sequence of nucleotides, the aim is to predict the base pairs formed in its three dimensional conformation. The inverse problem of designing a sequence folding into a particular target structure has only more recently received notable interest. With a growing appreciation and understanding of the functional and structural properties of RNA motifs, and a growing interest in utilising biomolecules in nano-scale designs, the interest in the inverse RNA folding problem is bound to increase. However, whereas the RNA folding problem from an algorithmic viewpoint has an elegant and efficient solution, the inverse RNA folding problem appears to be hard. Results In this paper we present a genetic algorithm approach to solve the inverse folding problem. The main aims of the development was to address the hitherto mostly ignored extension of solving the inverse folding problem, the multi-target inverse folding problem, while simultaneously designing a method with superior performance when measured on the quality of designed sequences. The genetic algorithm has been implemented as a Python program called Frnakenstein. It was benchmarked against four existing methods and several data sets totalling 769 real and predicted single structure targets, and on 292 two structure targets. It performed as well as or better at finding sequences which folded in silico into the target structure than all existing methods, without the heavy bias towards CG base pairs that was observed for all other top performing methods. On the two structure targets it also performed well, generating a perfect design for about 80% of the targets. Conclusions Our method illustrates that successful designs for the inverse RNA folding problem does not necessarily have to rely on heavy biases in base pair and unpaired base distributions. The design problem seems to become more
Dynamic Inversion of Intraslab Intermediate Depth Earthquakes
Madariaga, R. I.; Ruiz, S.
2011-12-01
We perform kinematic and dynamic inversions of the 24 July 2008 (Mw=6.8) Iwate northern Japan and 16 December 2007 (Mw 6.8) Michilla, Chile earthquakes using near field strong motion digital data. The data were filtered between 0.02 - 1 Hz. The rupture process is simulated with elliptical patches because we are looking for the average properties of the seismic rupture. The direct dynamic simulation problem was solved by a combination of finite difference modeling on a 32 km3 grid with 200 m spacing, and propagation from source to recorders using the AXITRA spectral program. For both earthquakes we used layered models of the structure. The Neighborhood algorithm and Monte Carlo methods are used to obtain the best fitting solutions and to explore the solution space. The optimum solutions are found comparing observed and synthetic records using an L2 norm. Both kinematic and dynamic inversions fit the observed data with misfits lower than 0.3. For both earthquakes, kinematic inversion shows strong trade-off between rupture velocity and maximum slip although the seismic moment remains invariant. Rupture velocities vary between sub-shear speeds to almost Rayleigh wave speeds. In the dynamic inversions 10 seismic source parameters were inverted for the Michilla earthquake and 8 parameters for the Iwate event, among them stress, friction and geometrical parameters. For the Iwate event the properties of the initial asperity at the source were not inverted because they could not be resolved by the data. In the dynamic inversion we observed a strong trade off among the friction law parameters. The best dynamic models form a family of that shares similar values of seismic moment and kappa (the ratio of released strain energy to energy release rate for friction). Kinematic and dynamic inversions in the 0.02 - 1 Hz frequency range form a set of non-unique solutions controlled by specific combinations of seismic source parameters. We discuss the origin of the non-uniqueness of
International Nuclear Information System (INIS)
Kishimoto, M.; Sakasai, K.; Ara, K.
1994-01-01
In this paper, the new type of non-invasive beam profile monitor for intense ion accelerator using high-temperature superconductor. We regard the inverse estimation problem of beam profile as the optimum allocation problem of the currents into the cross-section of the beam vacuum pipe and applied genetic algorithm to solve this optimization problem. And we carried out the computer simulation to verify the effectiveness of this inverse estimation method of beam profile. (author)
The inverse problems of wing panel manufacture processes
Oleinikov, A. I.; Bormotin, K. S.
2013-12-01
It is shown that inverse problems of steady-state creep bending of plates in both the geometrically linear and nonlinear formulations can be represented in a variational formulation. Steady-state values of the obtained functionals corresponding to the solutions of the problems of inelastic deformation and springback are determined by applying a finite element procedure to the functionals. Optimal laws of creep deformation are formulated using the criterion of minimizing damage in the functionals of the inverse problems. The formulated problems are reduced to the problems solved by the finite element method using MSC.Marc software. Currently, forming of light metals poses tremendous challenges due to their low ductility at room temperature and their unusual deformation characteristics at hot-cold work: strong asymmetry between tensile and compressive behavior, and a very pronounced anisotropy. We used the constitutive models of steady-state creep of initially transverse isotropy structural materials the kind of the stress state has influence. The paper gives basics of the developed computer-aided system of design, modeling, and electronic simulation targeting the processes of manufacture of wing integral panels. The modeling results can be used to calculate the die tooling, determine the panel processibility, and control panel rejection in the course of forming.
Dependence of paracentric inversion rate on tract length
DEFF Research Database (Denmark)
York, Thomas L; Durrett, Rick; Nielsen, Rasmus
2007-01-01
BACKGROUND: We develop a Bayesian method based on MCMC for estimating the relative rates of pericentric and paracentric inversions from marker data from two species. The method also allows estimation of the distribution of inversion tract lengths. RESULTS: We apply the method to data from...... Drosophila melanogaster and D. yakuba. We find that pericentric inversions occur at a much lower rate compared to paracentric inversions. The average paracentric inversion tract length is approx. 4.8 Mb with small inversions being more frequent than large inversions.If the two breakpoints defining...... a paracentric inversion tract are uniformly and independently distributed over chromosome arms there will be more short tract-length inversions than long; we find an even greater preponderance of short tract lengths than this would predict. Thus there appears to be a correlation between the positions...
International Nuclear Information System (INIS)
Choi, C. Y.
1997-01-01
A geometrical inverse heat conduction problem is solved for the infrared scanning cavity detection by the boundary element method using minimal energy technique. By minimizing the kinetic energy of temperature field, boundary element equations are converted to the quadratic programming problem. A hypothetical inner boundary is defined such that the actual cavity is located interior to the domain. Temperatures at hypothetical inner boundary are determined to meet the constraints of measurement error of surface temperature obtained by infrared scanning, and then boundary element analysis is performed for the position of an unknown boundary (cavity). Cavity detection algorithm is provided, and the effects of minimal energy technique on the inverse solution method are investigated by means of numerical analysis
SISYPHUS: A high performance seismic inversion factory
Gokhberg, Alexey; Simutė, Saulė; Boehm, Christian; Fichtner, Andreas
2016-04-01
In the recent years the massively parallel high performance computers became the standard instruments for solving the forward and inverse problems in seismology. The respective software packages dedicated to forward and inverse waveform modelling specially designed for such computers (SPECFEM3D, SES3D) became mature and widely available. These packages achieve significant computational performance and provide researchers with an opportunity to solve problems of bigger size at higher resolution within a shorter time. However, a typical seismic inversion process contains various activities that are beyond the common solver functionality. They include management of information on seismic events and stations, 3D models, observed and synthetic seismograms, pre-processing of the observed signals, computation of misfits and adjoint sources, minimization of misfits, and process workflow management. These activities are time consuming, seldom sufficiently automated, and therefore represent a bottleneck that can substantially offset performance benefits provided by even the most powerful modern supercomputers. Furthermore, a typical system architecture of modern supercomputing platforms is oriented towards the maximum computational performance and provides limited standard facilities for automation of the supporting activities. We present a prototype solution that automates all aspects of the seismic inversion process and is tuned for the modern massively parallel high performance computing systems. We address several major aspects of the solution architecture, which include (1) design of an inversion state database for tracing all relevant aspects of the entire solution process, (2) design of an extensible workflow management framework, (3) integration with wave propagation solvers, (4) integration with optimization packages, (5) computation of misfits and adjoint sources, and (6) process monitoring. The inversion state database represents a hierarchical structure with
Energy Technology Data Exchange (ETDEWEB)
Agullo, Y.
2005-09-15
This thesis present the extension of mono-component seismic pre-stack data stratigraphical inversion method to multicomponent data, with the objective of improving the determination of reservoir elastic parameters. In addiction to the PP pressure waves, the PS converted waves proved their interest for imaging under gas clouds; and their potential is highly significant for the characterization of lithologies, fluids, fractures... Nevertheless the simultaneous use ol PP and PS data remains problematic because of their different the time scales. To jointly use the information contained in PP and PS data, we propose a method in three steps first, mono-component stratigraphic inversions of PP then PS data; second, estimation of the PP to PS time conversion law; third, multicomponent stratigraphic inversion. For the second point, the estimation of the PP to PS conversion law is based on minimizing the difference between the S impedances obtained from PP and PS mono-component stratigraphic inversion. The pre-stack mono-component stratigraphic inversions was adapted to the case of multicomponent data by leaving each type of data in its own time scale in order to avoid the distortion of the seismic wavelet. The results obtained on a realistic synthetic PP-PS case show on one hand that determining PP to PS conversion law (from the mono-component inversion results) is feasible, and on the other hand that the joint inversion of PP and PS data with this conversion law improves the results compared to the mono-component inversion ones. Although this is presented within the framework of the PP and PS multi-component data, the developed methodology adapts directly to PP and SS data for example. (author)
Heriyanto, Mohammad; Srigutomo, Wahyu
2017-01-01
Exploration of natural or energy resources requires geophysical survey to determine the subsurface structure, such as DC resistivity method. In this research, field and synthetic data were used using Schlumberger configuration. One-dimensional (1-D) DC resistivity inversion was carried out using Singular Value Decomposition (SVD) and Levenberg-Marquardt (LM) techniques to obtain layered resistivity structure. We have developed software to perform both inversion met...
Inverse-Leidenfrost phenomenon on nanofiber mats on hot surfaces.
Weickgenannt, Christina M; Zhang, Yiyun; Sinha-Ray, Suman; Roisman, Ilia V; Gambaryan-Roisman, Tatiana; Tropea, Cameron; Yarin, Alexander L
2011-09-01
The Leidenfrost effect is a technically and industrially important phenomenon that severely restricts heat removal from high-heat-flux surfaces. A simple remedy to the Leidenfrost effect is provided by polymer nanofiber mats created and deposited by electrospinning on stainless steel surfaces. The influence of nanofiber mats on hydrodynamics and cooling efficiency of single drop impact onto hot surfaces has been investigated experimentally. The evolution of the drops has been recorded by a high-speed complimentary metal-oxide semiconductor camera, whereas the cooling temperature was measured by a thermocouple. A remarkable phenomenon was discovered: a mat of polymer nanofibers electrospun onto a heater surface can completely suppress the Leidenfrost effect, thereby increasing the rate of heat removal from the surface to the liquid drops significantly. The "inverse-Leidenfrost" effect is described qualitatively and quantitatively, providing clear physical reasons for the observed behavior.
NON-INVASIVE INVERSE PROBLEM IN CIVIL ENGINEERING
Directory of Open Access Journals (Sweden)
Jan Havelka
2017-11-01
Full Text Available In this contribution we focus on recovery of spatial distribution of material parameters utilizing only non-invasive boundary measurements. Such methods has gained its importance as imaging techniques in medicine, geophysics or archaeology. We apply similar principles for non-stationary heat transfer in civil engineering. In oppose to standard technique which rely on external loading devices, we assume the natural fluctuation of temperature throughout day and night can provide sufficient information to recover the underlying material parameters. The inverse problem was solved by a modified regularised Gauss-Newton iterative scheme and the underlying forward problem is solved with a finite element space-time discretisation. We show a successful reconstruction of material parameters on a synthetic example with real measurements. The virtual experiment also reveals the insensitivity to practical precision of sensor measurements.
On the calibration process of film dosimetry: OLS inverse regression versus WLS inverse prediction
International Nuclear Information System (INIS)
Crop, F; Thierens, H; Rompaye, B Van; Paelinck, L; Vakaet, L; Wagter, C De
2008-01-01
The purpose of this study was both putting forward a statistically correct model for film calibration and the optimization of this process. A reliable calibration is needed in order to perform accurate reference dosimetry with radiographic (Gafchromic) film. Sometimes, an ordinary least squares simple linear (in the parameters) regression is applied to the dose-optical-density (OD) curve with the dose as a function of OD (inverse regression) or sometimes OD as a function of dose (inverse prediction). The application of a simple linear regression fit is an invalid method because heteroscedasticity of the data is not taken into account. This could lead to erroneous results originating from the calibration process itself and thus to a lower accuracy. In this work, we compare the ordinary least squares (OLS) inverse regression method with the correct weighted least squares (WLS) inverse prediction method to create calibration curves. We found that the OLS inverse regression method could lead to a prediction bias of up to 7.3 cGy at 300 cGy and total prediction errors of 3% or more for Gafchromic EBT film. Application of the WLS inverse prediction method resulted in a maximum prediction bias of 1.4 cGy and total prediction errors below 2% in a 0-400 cGy range. We developed a Monte-Carlo-based process to optimize calibrations, depending on the needs of the experiment. This type of thorough analysis can lead to a higher accuracy for film dosimetry
Thermal hydraulic analysis of flow inversion in a research reactor with downward core cooling
Energy Technology Data Exchange (ETDEWEB)
Jo, Dae Seong; Park, Jong Hark; Chae, Hee Taek [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2011-10-15
Research reactors with forced downward core cooling experience flow inversion if the primary cooling pump (PCP) is failed. If PCP failure occurs, the downward flow decreases into zero flow and eventually turn into upward flow by natural circulation. During flow inversion phenomenon, reactor cores may undergo the most unfavorable thermal hydraulic condition, which results in the highest coolant and fuel temperatures and lowest thermal margins. The transient thermal hydraulic analyses of loss of flow accidents (LOFA) in IAEA 10MW benchmark MTR research reactor have been widely investigated by many institutes. In this study, a transient thermal hydraulic model of flow inversion is developed and applied to IAEA 10MW benchmark MTR research reactor. The results are compared against other analyses
Facies Constrained Elastic Full Waveform Inversion
Zhang, Z.
2017-05-26
Current efforts to utilize full waveform inversion (FWI) as a tool beyond acoustic imaging applications, for example for reservoir analysis, face inherent limitations on resolution and also on the potential trade-off between elastic model parameters. Adding rock physics constraints does help to mitigate these issues. However, current approaches to add such constraints are based on averaged type rock physics regularization terms. Since the true earth model consists of different facies, averaging over those facies naturally leads to smoothed models. To overcome this, we propose a novel way to utilize facies based constraints in elastic FWI. A so-called confidence map is calculated and updated at each iteration of the inversion using both the inverted models and the prior information. The numerical example shows that the proposed method can reduce the cross-talks and also can improve the resolution of inverted elastic properties.
Application of inversions to lossless image compression
Arnavut, Ziya
1997-04-01
Linear prediction schemes, such as that of the Joint Photographic Experts Group (JPEG), are simple and normally produces a residual sequence with lower zero-order entry. Occasionally the entropy of the prediction error becomes greater than that of the original image. Such situations frequently occur when the image data have discrete gray levels located within certain intervals. To alleviate this problem, various authors have suggested different preprocessing methods. However, the techniques reported require two passes. We extend the definition of Lehmer-type inversions (Lehmer 1950 and 1964) from permutations to multiset permutations and present a one-pass algorithm based on inversions of a multiset permutation. We obtain comparable results when we apply JPEG and even better results when we apply some other linear prediction schemes on a preprocessed image, which is treated as multiset permutation.
Optical inverse-square displacement sensor
Howe, R.D.; Kychakoff, G.
1989-09-12
This invention comprises an optical displacement sensor that uses the inverse-square attenuation of light reflected from a diffused surface to calculate the distance from the sensor to the reflecting surface. Light emerging from an optical fiber or the like is directed onto the surface whose distance is to be measured. The intensity I of reflected light is angle dependent, but within a sufficiently small solid angle it falls off as the inverse square of the distance from the surface. At least a pair of optical detectors are mounted to detect the reflected light within the small solid angle, their ends being at different distances R and R + [Delta]R from the surface. The distance R can then be found in terms of the ratio of the intensity measurements and the separation length as given in an equation. 10 figs.
Function representation with circle inversion map systems
Boreland, Bryson; Kunze, Herb
2017-01-01
The fractals literature develops the now well-known concept of local iterated function systems (using affine maps) with grey-level maps (LIFSM) as an approach to function representation in terms of the associated fixed point of the so-called fractal transform. While originally explored as a method to achieve signal (and 2-D image) compression, more recent work has explored various aspects of signal and image processing using this machinery. In this paper, we develop a similar framework for function representation using circle inversion map systems. Given a circle C with centre õ and radius r, inversion with respect to C transforms the point p˜ to the point p˜', such that p˜ and p˜' lie on the same radial half-line from õ and d(õ, p˜)d(õ, p˜') = r2, where d is Euclidean distance. We demonstrate the results with an example.
Voxel inversion of airborne EM data
DEFF Research Database (Denmark)
Fiandaca, Gianluca G.; Auken, Esben; Christiansen, Anders Vest C A.V.C.
2013-01-01
of prior information. Inversion of geophysical data usually refers to a model space being linked to the actual observation points. For airborne surveys the spatial discretization of the model space reflects the flight lines. Often airborne surveys are carried out in areas where other ground-based...... geophysical data are available. The model space of geophysical inversions is usually referred to the positions of the measurements, and ground-based model positions do not generally coincide with the airborne model positions. Consequently, a model space based on the measuring points is not well suited...... for jointly inverting airborne and ground-based geophysical data. Furthermore, geological and groundwater models most often refer to a regular voxel grid not correlated to the geophysical model space, and incorporating the geophysical data into the geological/hydrological modelling grids is problematic. We...
Inverse Faraday effect with plasmon beams
International Nuclear Information System (INIS)
Ali, S; Mendonca, J T
2011-01-01
The angular momentum conservation equation is considered for an electron gas, in the presence of Laguerre-Gaussian (LG) plasmons propagating along the z-axis. The LG plasmons carry a finite orbital angular momentum despite longitudinal nature, which can be partly transfered to the electrons. For short timescales, such that ion motion can be neglected, plasmons primarily interact with the electrons, creating an azimuthal electric field and generating an axial magnetic field. This effect can be called an inverse Faraday effect due to plasmons. Numerically, it is found that the magnitude of the magnetic field enhances with the plasmon density or with the energy of the electron plasma waves. A comparison of the magnitudes of the axial magnetic field is made for the inverse Faraday effect excited by both plasmons and transverse photons.
Inverse Kinematics of Concentric Tube Steerable Needles.
Sears, Patrick; Dupont, Pierre E
2007-01-01
Prior papers have introduced steerable needles composed of precurved concentric tubes. The curvature and extent of these needles can be controlled by the relative rotation and translation of the individual tubes. Under certain assumptions on the geometry and design of these needles, the forward kinematics problem can be solved in closed form by means of algebraic equations. The inverse kinematics problem, however, is not as straightforward owing to the nonlinear map between relative tube displacements and needle tip configuration as well as to the multiplicity of solutions as the number of tubes increases. This paper presents a general approach to solving the inverse kinematics problem using a pseudoinverse solution together with gradients of nullspace potential functions to enforce geometric and mechanical constraints.
Analog fault diagnosis by inverse problem technique
Ahmed, Rania F.
2011-12-01
A novel algorithm for detecting soft faults in linear analog circuits based on the inverse problem concept is proposed. The proposed approach utilizes optimization techniques with the aid of sensitivity analysis. The main contribution of this work is to apply the inverse problem technique to estimate the actual parameter values of the tested circuit and so, to detect and diagnose single fault in analog circuits. The validation of the algorithm is illustrated through applying it to Sallen-Key second order band pass filter and the results show that the detecting percentage efficiency was 100% and also, the maximum error percentage of estimating the parameter values is 0.7%. This technique can be applied to any other linear circuit and it also can be extended to be applied to non-linear circuits. © 2011 IEEE.
Radon concentration inversions in the troposphere
International Nuclear Information System (INIS)
Pereira, E.B.
1987-07-01
Vertical concentrations of radon in the lower troposphere were obtained in Southern Brazil up to 7Km high and have shown unexpected inverted profiles. The presence of low pressure center systems southwest to the flight path suggested that inversions might have been originated by a vertical transport mechanism based on the large scale circulation of developing synoptic systems. A simple friction-driven circulation model was contructed and the transport equation was solved. (author) [pt
Inverse folding of RNA pseudoknot structures
Directory of Open Access Journals (Sweden)
Li Linda YM
2010-06-01
Full Text Available Abstract Background RNA exhibits a variety of structural configurations. Here we consider a structure to be tantamount to the noncrossing Watson-Crick and G-U-base pairings (secondary structure and additional cross-serial base pairs. These interactions are called pseudoknots and are observed across the whole spectrum of RNA functionalities. In the context of studying natural RNA structures, searching for new ribozymes and designing artificial RNA, it is of interest to find RNA sequences folding into a specific structure and to analyze their induced neutral networks. Since the established inverse folding algorithms, RNAinverse, RNA-SSD as well as INFO-RNA are limited to RNA secondary structures, we present in this paper the inverse folding algorithm Inv which can deal with 3-noncrossing, canonical pseudoknot structures. Results In this paper we present the inverse folding algorithm Inv. We give a detailed analysis of Inv, including pseudocodes. We show that Inv allows to design in particular 3-noncrossing nonplanar RNA pseudoknot 3-noncrossing RNA structures-a class which is difficult to construct via dynamic programming routines. Inv is freely available at http://www.combinatorics.cn/cbpc/inv.html. Conclusions The algorithm Inv extends inverse folding capabilities to RNA pseudoknot structures. In comparison with RNAinverse it uses new ideas, for instance by considering sets of competing structures. As a result, Inv is not only able to find novel sequences even for RNA secondary structures, it does so in the context of competing structures that potentially exhibit cross-serial interactions.
The solution of nitrogen inversion in amidases.
Syrén, Per-Olof
2013-07-01
An important mechanistic aspect of enzyme catalyzed amide bond hydrolysis is the specific orientation of the lone pair of the nitrogen of the scissile amide bond during catalysis. As discussed in the literature during the last decades, stereoelectronic effects cause the single lone pair in the formed tetrahedral intermediate to be situated in a non-productive conformation in the enzyme active site and hence nitrogen inversion or rotation is necessary. By discussing recent mechanistic findings in the literature relevant for the conformation of the lone pair of the reacting amide nitrogen atom, it will be demonstrated that nature has evolved at least two catalytic strategies to cope with the stereoelectronic constraints inherent to amide bond hydrolysis regardless of the fold or catalytic mechanism. One solution to the inversion problem is to stabilize the transition state of inversion by hydrogen bond formation; another is to introduce a concerted proton shuttle mechanism that avoids inversion and delivers a hydrogen to the lone pair. By using molecular modeling it is demonstrated that the H-bond strategy is general and can be expanded to include many amidases/proteases with important metabolic functions, including the proteasome. Some examples of the proton shuttle mechanism will also be mentioned. To complete the picture of efficient enzyme catalyzed amide bond hydrolysis, general interactions in the active site of these catalysts will be discussed. An expanded knowledge of the prerequisites of efficient amide bond hydrolysis beyond the oxyanion hole and the catalytic dyad/triad will be of importance for enzyme and drug design. © 2013 The Author Journal compilation © 2013 FEBS.
Approximate Inverse Preconditioners with Adaptive Dropping
Czech Academy of Sciences Publication Activity Database
Kopal, J.; Rozložník, Miroslav; Tůma, Miroslav
2015-01-01
Roč. 84, June (2015), s. 13-20 ISSN 0965-9978 R&D Projects: GA ČR(CZ) GAP108/11/0853; GA ČR GA13-06684S Institutional support: RVO:67985807 Keywords : approximate inverse * Gram-Schmidt orthogonalization * incomplete decomposition * preconditioned conjugate gradient method * algebraic preconditioning * pivoting Subject RIV: BA - General Mathematics Impact factor: 1.673, year: 2015
Robust inversion via semistochastic dimensionality reduction
Aravkin, Aleksandr; Friedlander, Michael P.; van Leeuwen, Tristan
2011-01-01
We consider a class of inverse problems where it is possible to aggregate the results of multiple experiments. This class includes problems where the forward model is the solution operator to linear ODEs or PDEs. The tremendous size of such problems motivates dimensionality reduction techniques based on randomly mixing experiments. These techniques break down, however, when robust data-fitting formulations are used, which are essential in cases of missing data, unusually large errors, and sys...
Elastic versus acoustic inversion for marine surveys
Mora, Peter
2018-04-24
Full Wavefield Inversion (FWI) is a powerful and elegant approach for seismic imaging that is on the way to becoming the method of choice when processing exploration or global seismic data. In the case of processing marine survey data, one may be tempted to assume acoustic FWI is sufficient given that only pressure waves exist in the water layer. In this paper, we pose the question as to whether or not in theory – at least for a hard water bottom case – it should be possible to resolve the shear modulus or S-wave velocity in a marine setting using large offset data. We therefore conduct numerical experiments with idealized marine data calculated with the elastic wave equation. We study two cases, FWI of data due to a diffractor model, and FWI of data due to a fault model. We find that at least in idealized situation, elastic FWI of hard waterbottom data is capable of resolving between the two Lamé parameters λ and μ. Another numerical experiment with a soft waterbottom layer gives the same result. In contrast, acoustic FWI of the synthetic elastic data results in a single image of the first Lamé parameter λ which contains severe artefacts for diffraction data and noticable artefacts for layer reflection data. Based on these results, it would appear that at least, inversions of large offset marine data should be fully elastic rather than acoustic unless it has been demonstrated that for the specific case in question (offsets, model and water depth, practical issues such as soft sediment attenuation of shear waves or computational time), that an acoustic only inversion provides a reasonably good quality of image comparable to that of an elastic inversion. Further research with real data is required to determine the degree to which practical issues such as shear wave attenuation in soft sediments may affect this result.
On some inverse problems in nuclear physics
Belashev, B. Z.; Suleymanov, M. K.
2001-01-01
Some inverse problems in high-energy physics, neutron diffraction and NMR spectroscopy are discussed. To solve them, the Fourier integrated transformation method and the Maximum Entropy Technique (MENT) were used. The integrated images of experimental distributions are shown to be informative when determining the space-time parameters of a particle generation zone and when analysing blurred spectra. The efficiency of the above methods was checked by comparing relevant results with the results...
Geoacoustic inversion using the vector field
Crocker, Steven E.
The main goal of this project was to study the use of the acoustic vector field, separately or in combination with the scalar field, to estimate the depth dependent geoacoustic properties of the seafloor via non-linear inversion. The study was performed in the context of the Sediment Acoustics Experiment 2004 (SAX04) conducted in the Northern Gulf of Mexico (GOM) where a small number of acoustic vector sensors were deployed in close proximity to the seafloor. A variety of acoustic waveforms were transmitted into the seafloor at normal incidence. The acoustic vector sensors were located both above and beneath the seafloor interface where they measured the acoustic pressure and the acoustic particle acceleration. Motion data provided by the buried vector sensors were affected by a suspension response that was sensitive to the mass properties of the sensor, the sediment density and sediment elasticity (e.g., shear wave speed). The suspension response for the buried vector sensors included a resonance within the analysis band of 0.4 to 2.0 kHz. The suspension resonance represented an unknown complex transfer function between the acoustic vector field in the seabed and data representing that field. Therefore, inverse methods developed for this study were required to 1) estimate dynamic properties of the sensor suspension resonance and 2) account for the associated corruption of vector field data. A method to account for the vector sensor suspense response function was integrated directly into the inversion methods such that vector channel data corruption was reduced and an estimate of the shear wave speed in the sediment was returned. Inversions of real and synthetic data sets indicated that information about sediment shear wave speed was carried by the suspension response of the buried sensors, as opposed to being contained inherently within the acoustic vector field.
Differential equations inverse and direct problems
Favini, Angelo
2006-01-01
DEGENERATE FIRST ORDER IDENTIFICATION PROBLEMS IN BANACH SPACES A NONISOTHERMAL DYNAMICAL GINZBURG-LANDAU MODEL OF SUPERCONDUCTIVITY. EXISTENCE AND UNIQUENESS THEOREMSSOME GLOBAL IN TIME RESULTS FOR INTEGRODIFFERENTIAL PARABOLIC INVERSE PROBLEMSFOURTH ORDER ORDINARY DIFFERENTIAL OPERATORS WITH GENERAL WENTZELL BOUNDARY CONDITIONSTUDY OF ELLIPTIC DIFFERENTIAL EQUATIONS IN UMD SPACESDEGENERATE INTEGRODIFFERENTIAL EQUATIONS OF PARABOLIC TYPE EXPONENTIAL ATTRACTORS FOR SEMICONDUCTOR EQUATIONSCONVERGENCE TO STATIONARY STATES OF SOLUTIONS TO THE SEMILINEAR EQUATION OF VISCOELASTICITY ASYMPTOTIC BEHA
Full-waveform inversion: Filling the gaps
Beydoun, Wafik B.
2015-09-01
After receiving an outstanding response to its inaugural workshop in 2013, SEG once again achieved great success with its 2015 SEG Middle East Workshop, “Full-waveform inversion: Filling the gaps,” which took place 30 March–1 April 2015 in Abu Dhabi, UAE. The workshop was organized by SEG, and its partner sponsors were Saudi Aramco (gold sponsor), ExxonMobil, and CGG. Read More: http://library.seg.org/doi/10.1190/tle34091106.1
Inverse Bremsstrahlung in Astrophysical Plasmas: The Absorption ...
Indian Academy of Sciences (India)
(λ, T ; Ne,Ni) = k q.c. i.b.. (λ, T ; Ne,Ni) · Gi.b.(λ, T ),. (2) where Gi.b.(λ, T ) is the sought Gaunt factor. The determination of such averaged. Gaunt factor as a function of λ and T was the object of investigation in majority of the previous papers devoted to the inverse Bremsstrahlung process. This is illustrated in Figure 1, where ...
Inverse Scattering in a Multipath Environment
Directory of Open Access Journals (Sweden)
A. Cuccaro
2016-09-01
Full Text Available In this contribution an inverse scattering problem is ad- dressed in a multipath environment. In particular, multipath is created by known ”extra” point-like scatterers (passive elements expressely deployed between the scene under in- vestigation and the source/measurement domains. Through a back-projection imaging scheme, the role of the passive elements on the achievable performance is shown and com- pared to the free-space case.
Classical geometry Euclidean, transformational, inversive, and projective
Leonard, I E; Liu, A C F; Tokarsky, G W
2014-01-01
Features the classical themes of geometry with plentiful applications in mathematics, education, engineering, and science Accessible and reader-friendly, Classical Geometry: Euclidean, Transformational, Inversive, and Projective introduces readers to a valuable discipline that is crucial to understanding bothspatial relationships and logical reasoning. Focusing on the development of geometric intuitionwhile avoiding the axiomatic method, a problem solving approach is encouraged throughout. The book is strategically divided into three sections: Part One focuses on Euclidean geometry, which p
Metric entropy in linear inverse scattering
Directory of Open Access Journals (Sweden)
M. A. Maisto
2016-09-01
Full Text Available The role of multiple views and/or multiple frequencies on the achievable performance in linear inverse scattering problems is addressed. To this end, the impact of views and frequencies on the Kolmogorov entropy measure is studied. This way the metric information that can be conveyed back from data to the unknown can be estimated. For the sake of simplicity, the study deals with strip scatterers and the cases of discrete angles of incidence and/or frequencies.
Bayesian Inversion of Seabed Scattering Data
2014-09-30
using global optimization and Markov-chain Monte Carlo ( MCMC ) sampling algorithms. One of the goals of this work is to carry out inversions trans...is based on formulating the posterior probability density (PPD) of the model parameters of interest, which combines both data and prior information... posterior parameter uncertainty distributions, which quantify the effective data information content. In particular, scattering/geoacoustic parameter
Factorized Approximate Inverses With Adaptive Dropping
Czech Academy of Sciences Publication Activity Database
Kopal, Jiří; Rozložník, Miroslav; Tůma, Miroslav
2016-01-01
Roč. 38, č. 3 (2016), A1807-A1820 ISSN 1064-8275 R&D Projects: GA ČR GA13-06684S Grant - others:GA MŠk(CZ) LL1202 Institutional support: RVO:67985807 Keywords : approximate inverses * incomplete factorization * Gram–Schmidt orthogonalization * preconditioned iterative methods Subject RIV: BA - General Mathematics Impact factor: 2.195, year: 2016
An inverse approach for elucidating dendritic function
Directory of Open Access Journals (Sweden)
Benjamin Torben-Nielsen
2010-09-01
Full Text Available We outline an inverse approach for investigating dendritic function-structure relationships by optimizing dendritic trees for a-priori chosen computational functions. The inverse approach can be applied in two different ways. First, we can use it as a `hypothesis generator' in which we optimize dendrites for a function of general interest. The optimization yields an artificial dendrite that is subsequently compared to real neurons. This comparison potentially allows us to propose hypotheses about the function of real neurons. In this way, we investigated dendrites that optimally perform input-order detection. Second, we can use it as a `function confirmation' by optimizing dendrites for functions hypothesized to be performed by classes of neurons. If the optimized, artificial, dendrites resemble the dendrites of real neurons the artificial dendrites corroborate the hypothesized function of the real neuron. Moreover, properties of the artificial dendrites can lead to predictions about yet unmeasured properties. In this way, we investigated wide-field motion integration performed by the VS cells of the fly visual system. In outlining the inverse approach and two applications, we also elaborate on the nature of dendritic function. We furthermore discuss the role of optimality in assigning functions to dendrites and point out interesting future directions.
Solar structure inversion with LOWL data
Basu, Sarbani; Christensen-Dalsgaard, Joergen; Schou, Jesper; Thompson, Michael J.; Tomczyk, Steven
1995-01-01
Inversion results for the radial hydrostatic structure of the Sun, using six months of oscillation data obtained with the LOWL instrument, are presented. Both low and intermediate degree modes are used, thus avoiding the systematic errors that might have occurred in previous inversions by merging more than one data set. Using modes of between 0 deg and 90 deg and frequencies of between 1.5 mHz and 3.5 mHz, the variations with depth of the speed of sound, the density and the pressure were inferred for radii of between 0.05 and 0.85 stellar radius. It was found that in this region, the sound speed was within 0.15% of that of a model constructed using an equation of state that incorporated helium diffusion. The density difference between the Sun and the model was less than 0.8%. Given the small error bars on the inversion results, these differences are considered as being significant.
TOPICAL REVIEW: Inverse problems in elasticity
Bonnet, Marc; Constantinescu, Andrei
2005-04-01
This review is devoted to some inverse problems arising in the context of linear elasticity, namely the identification of distributions of elastic moduli, model parameters or buried objects such as cracks. These inverse problems are considered mainly for three-dimensional elastic media under equilibrium or dynamical conditions, and also for thin elastic plates. The main goal is to overview some recent results, in an effort to bridge the gap between studies of a mathematical nature and problems defined from engineering practice. Accordingly, emphasis is given to formulations and solution techniques which are well suited to general-purpose numerical methods for solving elasticity problems on complex configurations, in particular the finite element method and the boundary element method. An underlying thread of the discussion is the fact that useful tools for the formulation, analysis and solution of inverse problems arising in linear elasticity, namely the reciprocity gap and the error in constitutive equation, stem from variational and virtual work principles, i.e., fundamental principles governing the mechanics of deformable solid continua. In addition, the virtual work principle is shown to be instrumental for establishing computationally efficient formulae for parameter or geometrical sensitivity, based on the adjoint solution method. Sensitivity formulae are presented for various situations, especially in connection with contact mechanics, cavity and crack shape perturbations, thus enriching the already extensive known repertoire of such results. Finally, the concept of topological derivative and its implementation for the identification of cavities or inclusions are expounded.
Are Pericentric Inversions Reorganizing Wedge Shell Genomes?
Directory of Open Access Journals (Sweden)
Daniel García-Souto
2017-12-01
Full Text Available Wedge shells belonging to the Donacidae family are the dominant bivalves in exposed beaches in almost all areas of the world. Typically, two or more sympatric species of wedge shells differentially occupy intertidal, sublittoral, and offshore coastal waters in any given locality. A molecular cytogenetic analysis of two sympatric and closely related wedge shell species, Donax trunculus and Donax vittatus, was performed. Results showed that the karyotypes of these two species were both strikingly different and closely alike; whilst metacentric and submetacentric chromosome pairs were the main components of the karyotype of D. trunculus, 10–11 of the 19 chromosome pairs were telocentric in D. vittatus, most likely as a result of different pericentric inversions. GC-rich heterochromatic bands were present in both species. Furthermore, they showed coincidental 45S ribosomal RNA (rRNA, 5S rRNA and H3 histone gene clusters at conserved chromosomal locations, although D. trunculus had an additional 45S rDNA cluster. Intraspecific pericentric inversions were also detected in both D. trunculus and D. vittatus. The close genetic similarity of these two species together with the high degree of conservation of the 45S rRNA, 5S rRNA and H3 histone gene clusters, and GC-rich heterochromatic bands indicate that pericentric inversions contribute to the karyotype divergence in wedge shells.
Elastic reflection waveform inversion with variable density
Li, Yuanyuan
2017-08-17
Elastic full waveform inversion (FWI) provides a better description of the subsurface than those given by the acoustic assumption. However it suffers from a more serious cycle skipping problem compared with the latter. Reflection waveform inversion (RWI) provides a method to build a good background model, which can serve as an initial model for elastic FWI. Therefore, we introduce the concept of RWI for elastic media, and propose elastic RWI with variable density. We apply Born modeling to generate the synthetic reflection data by using optimized perturbations of P- and S-wave velocities and density. The inversion for the perturbations in P- and S-wave velocities and density is similar to elastic least-squares reverse time migration (LSRTM). An incorrect initial model will lead to some misfits at the far offsets of reflections; thus, can be utilized to update the background velocity. We optimize the perturbation and background models in a nested approach. Numerical tests on the Marmousi model demonstrate that our method is able to build reasonably good background models for elastic FWI with absence of low frequencies, and it can deal with the variable density, which is needed in real cases.
Computationally efficient Bayesian inference for inverse problems.
Energy Technology Data Exchange (ETDEWEB)
Marzouk, Youssef M.; Najm, Habib N.; Rahn, Larry A.
2007-10-01
Bayesian statistics provides a foundation for inference from noisy and incomplete data, a natural mechanism for regularization in the form of prior information, and a quantitative assessment of uncertainty in the inferred results. Inverse problems - representing indirect estimation of model parameters, inputs, or structural components - can be fruitfully cast in this framework. Complex and computationally intensive forward models arising in physical applications, however, can render a Bayesian approach prohibitive. This difficulty is compounded by high-dimensional model spaces, as when the unknown is a spatiotemporal field. We present new algorithmic developments for Bayesian inference in this context, showing strong connections with the forward propagation of uncertainty. In particular, we introduce a stochastic spectral formulation that dramatically accelerates the Bayesian solution of inverse problems via rapid evaluation of a surrogate posterior. We also explore dimensionality reduction for the inference of spatiotemporal fields, using truncated spectral representations of Gaussian process priors. These new approaches are demonstrated on scalar transport problems arising in contaminant source inversion and in the inference of inhomogeneous material or transport properties. We also present a Bayesian framework for parameter estimation in stochastic models, where intrinsic stochasticity may be intermingled with observational noise. Evaluation of a likelihood function may not be analytically tractable in these cases, and thus several alternative Markov chain Monte Carlo (MCMC) schemes, operating on the product space of the observations and the parameters, are introduced.
Constraining inverse curvature gravity with supernovae
Energy Technology Data Exchange (ETDEWEB)
Mena, Olga; Santiago, Jose; /Fermilab; Weller, Jochen; /University Coll., London /Fermilab
2005-10-01
We show that the current accelerated expansion of the Universe can be explained without resorting to dark energy. Models of generalized modified gravity, with inverse powers of the curvature can have late time accelerating attractors without conflicting with solar system experiments. We have solved the Friedman equations for the full dynamical range of the evolution of the Universe. This allows us to perform a detailed analysis of Supernovae data in the context of such models that results in an excellent fit. Hence, inverse curvature gravity models represent an example of phenomenologically viable models in which the current acceleration of the Universe is driven by curvature instead of dark energy. If we further include constraints on the current expansion rate of the Universe from the Hubble Space Telescope and on the age of the Universe from globular clusters, we obtain that the matter content of the Universe is 0.07 {le} {omega}{sub m} {le} 0.21 (95% Confidence). Hence the inverse curvature gravity models considered can not explain the dynamics of the Universe just with a baryonic matter component.
Polyphased Inversions of an Intracontinental Rift: Case Study of the Marrakech High Atlas, Morocco
Leprêtre, R.; Missenard, Y.; Barbarand, J.; Gautheron, C.; Jouvie, I.; Saddiqi, O.
2018-03-01
The High and Middle Atlas intraplate belts in Morocco correspond to Mesozoic rifted basins inverted during the Cenozoic during Africa/Eurasia convergence. The Marrakech High Atlas lies at a key location between Atlantic and Tethyan influences during the Mesozoic rifting phase but represents today high reliefs. Age and style of deformation and the mechanisms underlying the Cenozoic inversion are nevertheless still debated. To solve this issue, we produced new low-temperature thermochronology data (fission track and [U-Th]/He on apatite). Two cross sections were investigated in the western and eastern Marrakech High Atlas. Results of inverse modeling allow recognizing five cooling events attributed to erosion since Early Jurassic. Apart from a first erosional event from Middle/Late Jurassic to Early Cretaceous, four stages can be related to the convergence processes between Africa and Europe since the Late Cretaceous. Our data and thermal modeling results suggest that the inversion processes are guided at first order by the fault network inherited from the rifting episodes. The sedimentary cover and the Neogene lithospheric thinning produced a significant thermal weakening that facilitated the inversion of this ancient rift. Our data show that the Marrakech High Atlas has been behaving as a giant pop-up since the beginning of Cenozoic inversion stages.
Caught Red-Handed: A Novel Search for the Culprit Behind Thermal Inversions in Exoplanet Atmospheres
Kreidberg, Laura
2017-08-01
Thermal inversions have been one of the mostly hotly debated topics in exoplanet atmospheres over the last decade. Recent observations show conclusively that thermal inversions do exist for some of the most highly irradiated planets. The likeliest culprit for the inversions is strong absorption by titanium and vanadium oxide (TiO/VO) gas, which heats the upper atmosphere. However, TiO/VO have never been detected, despite many attempts. It is possible that these efforts failed because they focused on planets that were too cool, or were foiled by clouds and haze.We propose a novel search for TiO in the atmosphere of WASP-33b, a planet with a known thermal inversion (Haynes et al. 2015). We will measure the planet's thermal emission spectrum with the WFC3/G102 grism, where TiO is expected to have strong spectral features. This is the first proposed use of this grism for exoplanet emission spectroscopy. WASP-33b has the single highest signal-to-noise in thermal emission of any exoplanet known, and with one eclipse observation we will be sensitive to temperature differences in the upper atmosphere of 10 sigma) and definitively settle the thermal inversion debate.
International Nuclear Information System (INIS)
Salama, Amgad
2011-01-01
Highlights: → The 3D, CFD simulation of FLOFA accident in the generic IAEA 10 MW research reactor is carried out. → The different flow and heat transfer mechanisms involved in this process were elucidated. → The transition between these mechanisms during the course of FLOFA is discussed and investigated. → The interesting inversion process upon the transition from downward flow to upward flow is shown. → The temperature field and the friction coefficient during the whole transient process were shown. - Abstract: Three dimensional CFD full simulations of the fast loss of flow accident (FLOFA) of the IAEA 10 MW generic MTR research reactor are conducted. In this system the flow is initially downward. The transient scenario starts when the pump coasts down exponentially with a time constant of 1 s. As a result the temperatures of the heating element, the clad, and the coolant rise. When the flow reaches 85% of its nominal value the control rod system scrams and the power drops sharply resulting in the temperatures of the different components to drop. As the coolant flow continues to drop, the decay heat causes the temperatures to increase at a slower rate in the beginning. When the flow becomes laminar, the rate of temperature increase becomes larger and when the pumps completely stop a flow inversion occurs because of natural convection. The temperature will continue to rise at even higher rates until natural convection is established, that is when the temperatures settle off. The interesting 3D patterns of the flow during the inversion process are shown and investigated. The temperature history is also reported and is compared with those estimated by one-dimensional codes. Generally, very good agreement is achieved which provides confidence in the modeling approach.
Approximate inverse preconditioning of iterative methods for nonsymmetric linear systems
Energy Technology Data Exchange (ETDEWEB)
Benzi, M. [Universita di Bologna (Italy); Tuma, M. [Inst. of Computer Sciences, Prague (Czech Republic)
1996-12-31
A method for computing an incomplete factorization of the inverse of a nonsymmetric matrix A is presented. The resulting factorized sparse approximate inverse is used as a preconditioner in the iterative solution of Ax = b by Krylov subspace methods.
INVERSE ELECTRON TRANSFER IN PEROXYOXALATE CHEMIEXCITATION USING EASILY REDUCIBLE ACTIVATORS
Bartoloni, Fernando Heering; Monteiro Leite Ciscato, Luiz Francisco; Augusto, Felipe Alberto; Baader, Wilhelm Josef
2010-01-01
INVERSE ELECTRON TRANSFER IN PEROXYOXALATE CHEMIEXCITATION USING EASILY REDUCIBLE ACTIVATORS. Chemiluminescence properties of the peroxyoxalate reaction in the presence of activators bearing electron withdrawing substituents were studied, to evaluate the possible occurrence of an inverse electron
Probabilistic inversion in priority setting of emerging zoonoses.
Kurowicka, D.; Bucura, C.; Cooke, R.; Havelaar, A.H.
2010-01-01
This article presents methodology of applying probabilistic inversion in combination with expert judgment in priority setting problem. Experts rank scenarios according to severity. A linear multi-criteria analysis model underlying the expert preferences is posited. Using probabilistic inversion, a
Inverse problem of Ocean Acoustic Tomography (OAT) - A numerical experiment
Digital Repository Service at National Institute of Oceanography (India)
Murty, T.V.R.; Somayajulu, Y.K.; Mahadevan, R.; Murty, C.S.
Acoustic model simulation experiments related to the forward and inverse aspects of ocean tomography have been taken up with a view to estimate the vertical sound speed field by inverting the travel time data. Two methods of inversion have been...
Crestel, Benjamin; Alexanderian, Alen; Stadler, Georg; Ghattas, Omar
2017-07-01
The computational cost of solving an inverse problem governed by PDEs, using multiple experiments, increases linearly with the number of experiments. A recently proposed method to decrease this cost uses only a small number of random linear combinations of all experiments for solving the inverse problem. This approach applies to inverse problems where the PDE solution depends linearly on the right-hand side function that models the experiment. As this method is stochastic in essence, the quality of the obtained reconstructions can vary, in particular when only a small number of combinations are used. We develop a Bayesian formulation for the definition and computation of encoding weights that lead to a parameter reconstruction with the least uncertainty. We call these weights A-optimal encoding weights. Our framework applies to inverse problems where the governing PDE is nonlinear with respect to the inversion parameter field. We formulate the problem in infinite dimensions and follow the optimize-then-discretize approach, devoting special attention to the discretization and the choice of numerical methods in order to achieve a computational cost that is independent of the parameter discretization. We elaborate our method for a Helmholtz inverse problem, and derive the adjoint-based expressions for the gradient of the objective function of the optimization problem for finding the A-optimal encoding weights. The proposed method is potentially attractive for real-time monitoring applications, where one can invest the effort to compute optimal weights offline, to later solve an inverse problem repeatedly, over time, at a fraction of the initial cost.
Inverse problems in classical and quantum physics
International Nuclear Information System (INIS)
Almasy, A.A.
2007-01-01
The subject of this thesis is in the area of Applied Mathematics known as Inverse Problems. Inverse problems are those where a set of measured data is analysed in order to get as much information as possible on a model which is assumed to represent a system in the real world. We study two inverse problems in the fields of classical and quantum physics: QCD condensates from tau-decay data and the inverse conductivity problem. Despite a concentrated effort by physicists extending over many years, an understanding of QCD from first principles continues to be elusive. Fortunately, data continues to appear which provide a rather direct probe of the inner workings of the strong interactions. We use a functional method which allows us to extract within rather general assumptions phenomenological parameters of QCD (the condensates) from a comparison of the time-like experimental data with asymptotic space-like results from theory. The price to be paid for the generality of assumptions is relatively large errors in the values of the extracted parameters. Although we do not claim that our method is superior to other approaches, we hope that our results lend additional confidence to the numerical results obtained with the help of methods based on QCD sum rules. EIT is a technology developed to image the electrical conductivity distribution of a conductive medium. The technique works by performing simultaneous measurements of direct or alternating electric currents and voltages on the boundary of an object. These are the data used by an image reconstruction algorithm to determine the electrical conductivity distribution within the object. In this thesis, two approaches of EIT image reconstruction are proposed. The first is based on reformulating the inverse problem in terms of integral equations. This method uses only a single set of measurements for the reconstruction. The second approach is an algorithm based on linearisation which uses more then one set of measurements. A
Inverse problems in classical and quantum physics
Energy Technology Data Exchange (ETDEWEB)
Almasy, A.A.
2007-06-29
The subject of this thesis is in the area of Applied Mathematics known as Inverse Problems. Inverse problems are those where a set of measured data is analysed in order to get as much information as possible on a model which is assumed to represent a system in the real world. We study two inverse problems in the fields of classical and quantum physics: QCD condensates from tau-decay data and the inverse conductivity problem. Despite a concentrated effort by physicists extending over many years, an understanding of QCD from first principles continues to be elusive. Fortunately, data continues to appear which provide a rather direct probe of the inner workings of the strong interactions. We use a functional method which allows us to extract within rather general assumptions phenomenological parameters of QCD (the condensates) from a comparison of the time-like experimental data with asymptotic space-like results from theory. The price to be paid for the generality of assumptions is relatively large errors in the values of the extracted parameters. Although we do not claim that our method is superior to other approaches, we hope that our results lend additional confidence to the numerical results obtained with the help of methods based on QCD sum rules. EIT is a technology developed to image the electrical conductivity distribution of a conductive medium. The technique works by performing simultaneous measurements of direct or alternating electric currents and voltages on the boundary of an object. These are the data used by an image reconstruction algorithm to determine the electrical conductivity distribution within the object. In this thesis, two approaches of EIT image reconstruction are proposed. The first is based on reformulating the inverse problem in terms of integral equations. This method uses only a single set of measurements for the reconstruction. The second approach is an algorithm based on linearisation which uses more then one set of measurements. A
Inverse scattering problem in turbulent magnetic fluctuations
Directory of Open Access Journals (Sweden)
R. A. Treumann
2016-08-01
Full Text Available We apply a particular form of the inverse scattering theory to turbulent magnetic fluctuations in a plasma. In the present note we develop the theory, formulate the magnetic fluctuation problem in terms of its electrodynamic turbulent response function, and reduce it to the solution of a special form of the famous Gelfand–Levitan–Marchenko equation of quantum mechanical scattering theory. The last of these applies to transmission and reflection in an active medium. The theory of turbulent magnetic fluctuations does not refer to such quantities. It requires a somewhat different formulation. We reduce the theory to the measurement of the low-frequency electromagnetic fluctuation spectrum, which is not the turbulent spectral energy density. The inverse theory in this form enables obtaining information about the turbulent response function of the medium. The dynamic causes of the electromagnetic fluctuations are implicit to it. Thus, it is of vital interest in low-frequency magnetic turbulence. The theory is developed until presentation of the equations in applicable form to observations of turbulent electromagnetic fluctuations as input from measurements. Solution of the final integral equation should be done by standard numerical methods based on iteration. We point to the possibility of treating power law fluctuation spectra as an example. Formulation of the problem to include observations of spectral power densities in turbulence is not attempted. This leads to severe mathematical problems and requires a reformulation of inverse scattering theory. One particular aspect of the present inverse theory of turbulent fluctuations is that its structure naturally leads to spatial information which is obtained from the temporal information that is inherent to the observation of time series. The Taylor assumption is not needed here. This is a consequence of Maxwell's equations, which couple space and time evolution. The inversion procedure takes
Review of ankle inversion sprain simulators in the biomechanics laboratory
Ha, Sophia Chui-Wai; Fong, Daniel Tik-Pui; Chan, Kai-Ming
2015-01-01
Ankle inversion ligamentous sprain is one of the most common sports injuries. The most direct way is to investigate real injury incidents, but it is unethical and impossible to replicate on test participants. Simulators including tilt platforms, trapdoors, and fulcrum devices were designed to mimic ankle inversion movements in laboratories. Inversion angle was the only element considered in early designs; however, an ankle sprain is composed of inversion and plantarflexion in clinical observa...
The normal and inverse magnetocaloric effect in RCu2 (R=Tb, Dy, Ho, Er) compounds
International Nuclear Information System (INIS)
Zheng, X.Q.; Xu, Z.Y.; Zhang, B.; Hu, F.X.; Shen, B.G.
2017-01-01
Orthorhombic polycrystalline RCu 2 (R=Tb, Dy, Ho and Er) compounds were synthesized and the magnetic properties and magnetocaloric effect (MCE) were investigated in detail. All of the RCu 2 compounds are antiferromagnetic (AFM) ordered. As temperature increases, RCu 2 compounds undergo an AFM to AFM transition at T t and an AFM to paramagnetic (PM) transition at T N . Besides of the normal MCE around T N , large inverse MCE around T t was found in TbCu 2 compound. Under a field change of 0–7 T, the maximal value of inverse MCE is even larger than the value of normal MCE around T N for TbCu 2 compound. Considering of the normal and inverse MCE, TbCu 2 shows the largest refrigerant capacity among the RCu 2 (R=Tb, Dy, Ho and Er) compounds indicating its potential applications in low temperature multistage refrigeration. - Highlights: • Large inverse magnetocaloric effect is observed in TbCu 2 compound. • The AFM to AFM transition is observed in RCu 2 (R=Tb, Dy, Ho, Er) compounds. • The MCE performance of TbCu 2 compound is evaluated in a more comprehensively way.
Trace lithium is inversely associated with male suicide after adjustment of climatic factors.
Shiotsuki, Ippei; Terao, Takeshi; Ishii, Nobuyoshi; Takeuchi, Shouhei; Kuroda, Yoshiki; Kohno, Kentaro; Mizokami, Yoshinori; Hatano, Koji; Tanabe, Sanshi; Kanehisa, Masayuki; Iwata, Noboru; Matusda, Shinya
2016-01-01
Previously, we showed the inverse association between lithium in drinking water and male suicide in Kyushu Island. The narrow variation in meteorological factors of Kyushu Island and a considerable amount of evidence regarding the role of the factors on suicide provoked the necessities of adjusting the association by the wide variation in sunshine, temperature, rain fall, and snow fall. To keep the wide variation in meteorological factors, we combined the data of Kyushu (the southernmost city is Itoman, 26°) and Hokkaido (the northernmost city is Wakkanai, 45°). Multiple regression analyses were used to predict suicide SMRs (total, male and female) by lithium levels in drinking water and meteorological factors. After adjustment of meteorological factors, lithium levels were significantly and inversely associated with male suicide SMRs, but not with total or female suicide SMRs, across the 153 cities of Hokkaido and Kyushu Islands. Moreover, annual total sunshine and annual mean temperature were significantly and inversely associated with male suicide SMRs whereas annual total rainfall was significantly and directly associated with male suicide SMRs. The limitations of the present study include the lack of data relevant to lithium levels in food and the proportion of the population who drank tap water and their consumption habits. The present findings suggest that trace lithium is inversely associated with male but not female suicide after adjustment of meteorological factors. Copyright © 2015 Elsevier B.V. All rights reserved.
Large maneuverable flight control using neural networks dynamic inversion
Yang, Enquan; Gao, Jinyuan
2003-09-01
An adaptive dynamic-inversion-based neural network is applied to aircraft large maneuverable flight control. Neural network is used to cancel the inversion error which may arise from imperfect modeling or approximate inversion. Simulation results for an aircraft model are presented to illustrate the performance of the flight control system.
n-Colour even self-inverse compositions
Indian Academy of Sciences (India)
An -colour even self-inverse composition is defined as an -colour self-inverse composition with even parts. In this paper, we get generating functions, explicit formulas and recurrence formulas for -colour even self-inverse compositions. One new binomial identity is also obtained.
Inversion structures in Northern Sotho | Zerbian | Southern African ...
African Journals Online (AJOL)
Inversion structures, in which the logical subject appears in postverbal position, are a wide-spread phenomenon among Bantu languages. The paper presents an overview of inversion structures in Bantu languages and describes in detail the inversion constructions in the Southern Bantu language Northern Sotho. It argues ...
International Nuclear Information System (INIS)
El-Morshedy, Salah El-Din
2010-01-01
Research reactors of power greater than 20 MW are usually designed to be cooled with upward coolant flow direction inside the reactor core. This is mainly to prevent flow inversion problems following a pump coast down. However, in some designs and under certain operating conditions, flow inversion phenomenon is predicted. In the present work, the best-estimate Material Testing Reactors Thermal-Hydraulic Analysis program (MTRTHA) is used to simulate a typical MTR reactor behavior with upward cooling under a hypothetical case of loss of off-site power. The flow inversion phenomenon is predicted under certain decay heat and/or pool temperature values below the design values. The reactor simulation under loss of off-site power is performed for two cases namely; two-flap valves open and one flap-valve fails to open. The model results for the flow inversion phenomenon prediction is analyzed and a solution of the problem is suggested. (orig.)
Inverse planning for x-ray rotation therapy: a general solution of the inverse problem
International Nuclear Information System (INIS)
Oelfke, U.; Bortfeld, T.
1999-01-01
Rotation therapy with photons is currently under investigation for the delivery of intensity modulated radiotherapy (IMRT). An analytical approach for inverse treatment planning of this radiotherapy technique is described. The inverse problem for the delivery of arbitrary 2D dose profiles is first formulated and then solved analytically. In contrast to previously applied strategies for solving the inverse problem, it is shown that the most general solution for the fluence profiles consists of two independent solutions of different parity. A first analytical expression for both fluence profiles is derived. The mathematical derivation includes two different strategies, an elementary expansion of fluence and dose into polynomials and a more practical approach in terms of Fourier transforms. The obtained results are discussed in the context of previous work on this problem. (author)
Modeling Temperature and Pricing Weather Derivatives Based on Temperature
Directory of Open Access Journals (Sweden)
Birhan Taştan
2017-01-01
Full Text Available This study first proposes a temperature model to calculate the temperature indices upon which temperature-based derivatives are written. The model is designed as a mean-reverting process driven by a Levy process to represent jumps and other features of temperature. Temperature indices are mainly measured as deviations from a base temperature, and, hence, the proposed model includes jumps because they may constitute an important part of this deviation for some locations. The estimated value of a temperature index and its distribution in this model apply an inversion formula to the temperature model. Second, this study develops a pricing process over calculated index values, which returns a customized price for temperature-based derivatives considering that temperature has unique effects on every economic entity. This personalized price is also used to reveal the trading behavior of a hypothesized entity in a temperature-based derivative trade with profit maximization as the objective. Thus, this study presents a new method that does not need to evaluate the risk-aversion behavior of any economic entity.
A mechanism for the downturn in inverse susceptibility in triangle-based frustrated spin systems
International Nuclear Information System (INIS)
Isoda, M
2008-01-01
A mechanism for the downturn of inverse magnetic susceptibility below an intermediate temperature, recently observed in many experiments, is proposed as an intrinsic feature of lattices with triangle-based frustrated geometries. The temperature at the bending of the inverse susceptibility curve may be related to the features of other thermodynamic properties; the hump of the specific heat and the emergence of a 1/3 plateau in magnetization under a magnetic field. This fact is derived through a Monte Carlo simulation study of the Ising model on triangular and kagome lattices, and the exact calculation for the single and small-sized triangle clusters, on both the Ising and Heisenberg models. These results may indicate the dominance of S(S z ) = 1/2 quantum (classical) trimer formation in the intermediate-energy regime in two-dimensional triangle-based lattices
Constraining inverse-curvature gravity with supernovae.
Mena, Olga; Santiago, José; Weller, Jochen
2006-02-03
We show that models of generalized modified gravity, with inverse powers of the curvature, can explain the current accelerated expansion of the Universe without resorting to dark energy and without conflicting with solar system experiments. We have solved the Friedmann equations for the full dynamical range of the evolution of the Universe and performed a detailed analysis of supernovae data in the context of such models that results in an excellent fit. If we further include constraints on the current expansion of the Universe and on its age, we obtain that the matter content of the Universe is 0.07baryonic matter component.
Interferogram analysis using the Abel inversion technique
International Nuclear Information System (INIS)
Yusof Munajat; Mohamad Kadim Suaidi
2000-01-01
High speed and high resolution optical detection system were used to capture the image of acoustic waves propagation. The freeze image in the form of interferogram was analysed to calculate the transient pressure profile of the acoustic waves. The interferogram analysis was based on the fringe shift and the application of the Abel inversion technique. An easier approach was made by mean of using MathCAD program as a tool in the programming; yet powerful enough to make such calculation, plotting and transfer of file. (Author)
Transmuted New Generalized Inverse Weibull Distribution
Directory of Open Access Journals (Sweden)
Muhammad Shuaib Khan
2017-06-01
Full Text Available This paper introduces the transmuted new generalized inverse Weibull distribution by using the quadratic rank transmutation map (QRTM scheme studied by Shaw et al. (2007. The proposed model contains the twenty three lifetime distributions as special sub-models. Some mathematical properties of the new distribution are formulated, such as quantile function, Rényi entropy, mean deviations, moments, moment generating function and order statistics. The method of maximum likelihood is used for estimating the model parameters. We illustrate the flexibility and potential usefulness of the new distribution by using reliability data.
Multiscale phase inversion of seismic marine data
Fu, Lei
2017-08-17
We test the feasibility of applying multiscale phase inversion (MPI) to seismic marine data. To avoid cycle-skipping, the multiscale strategy temporally integrates the traces several times, i.e. high-order integration, to produce low-boost seismograms that are used as input data for the initial iterations of MPI. As the iterations proceed, higher frequencies in the data are boosted by using integrated traces of lower order as the input data. Results with synthetic data and field data from the Gulf of Mexico produce robust and accurate results if the model does not contain strong velocity contrasts such as salt-sediment interfaces.
Parallel block inversion of geophysical data
Pereyra, Victor L.
1993-12-01
We present an automatic blocking algorithm for some medium size nonlinear least squares problems that arise in the inversion of travel time data in geophysics. This blocking leads to a nonlinear Gauss-Seidel type iteration which can be distributed to a network of computers. The low dimensional blocks are also amenable to global optimization methods which leads to further parallelization. All this is necessary because the original problem is generally non- convex, ill-conditioned, with a goal functional that is very expensive to evaluate.
Thermodynamic inversion origin of living systems
Kompanichenko, Vladimir N
2017-01-01
This book discusses the theory, general principles, and energy source conditions allowing for the emergence of life in planetary systems. The author examines the material conditions found in natural hydrothermal sites, the appropriate analogs of prebiotic environments on early Earth. He provides an overview of current laboratory experiments in prebiotic materials chemistry and substantiation of a new direction for the experiments in the origin of life field. Describes thermodynamic inversion and how it relates to the living cell; Examines the current direction of experiments on prebiotic materials chemistry; Introduces and substantiates necessary conditions for the emergence of life.
Deep controls on intraplate basin inversion
DEFF Research Database (Denmark)
Nielsen, S.B.; Stephenson, Randell Alexander; Schiffer, Christian
2014-01-01
favourably orientated with respect to pre-existing structures in the lithosphere. Furthermore, stresses derived from lithospheric potential energy variations as well as those from plate boundary forces must be taken into account in order to explain intraplate seismicity and deformation such as basin......Basin inversion is an intermediate-scale manifestation of continental intraplate deformation, which produces earthquake activity in the interior of continents. The sedimentary basins of central Europe, inverted in the Late Cretaceous– Paleocene, represent a classic example of this phenomenon...
Review of ankle inversion sprain simulators in the biomechanics laboratory
Directory of Open Access Journals (Sweden)
Sophia Chui-Wai Ha
2015-10-01
Full Text Available Ankle inversion ligamentous sprain is one of the most common sports injuries. The most direct way is to investigate real injury incidents, but it is unethical and impossible to replicate on test participants. Simulators including tilt platforms, trapdoors, and fulcrum devices were designed to mimic ankle inversion movements in laboratories. Inversion angle was the only element considered in early designs; however, an ankle sprain is composed of inversion and plantarflexion in clinical observations. Inversion velocity is another parameter that increased the reality of simulation. This review summarised the simulators, and aimed to compare and contrast their features and settings.
Inversion Approach For Thermal Data From A Convecting Hydrothermal System
Energy Technology Data Exchange (ETDEWEB)
Kasameyer, P.; Younker, L.; Hanson, J.
1985-01-01
Hydrothermal systems are often studied by collecting thermal gradient data and temperature depth curves. These data contain important information about the flow field, the evolution of the hydrothermal system, and the location and nature of the ultimate heat sources. Thermal data are conventionally interpreted by the ''forward'' method; the thermal field is calculated based on selected initial conditions and boundary conditions such as temperature and permeability distributions. If the calculated thermal field matches the data, the chosen conditions are inferred to be possibly correct. Because many sets of initial conditions may produce similar thermal fields, users of the ''forward'' method may inadvertently miss the correct set of initial conditions. Analytical methods for ''inverting'' data also allow the determination of all the possible solutions consistent with the definition of the problem. In this paper we suggest an approach for inverting thermal data from a hydrothermal system, and compare it to the more conventional approach. We illustrate the difference in the methods by comparing their application to the Salton Sea Geothermal Field by Lau (1980a) and Kasameyer, et al. (1984). In this particular example, the inverse method was used to draw conclusions about the age and total rate of fluid flow into the hydrothermal system.
Energy Technology Data Exchange (ETDEWEB)
Lebrun, D.
1997-05-22
The aim of the dissertation is the linearized inversion of multicomponent seismic data for 3D elastic horizontally stratified media, using Born approximation. A Jacobian matrix is constructed; it will be used to model seismic data from elastic parameters. The inversion technique, relying on single value decomposition (SVD) of the Jacobian matrix, is described. Next, the resolution of inverted elastic parameters is quantitatively studies. A first use of the technique is shown in the frame of an evaluation of a sea bottom acquisition (synthetic data). Finally, a real data set acquired with conventional marine technique is inverted. (author) 70 refs.
Waite, A. J.; Swart, P. K.
2011-12-01
As aragonite is the metastable polymorph of calcium carbonate, it lends itself to monotropic inversion to the more stable polymorph, calcite. This inversion is possible through an increase in the temperature and pressure conditions to which the sample is exposed and, although first noted nearly a century ago, has been primarily discussed in the context of sample roasting prior to analyses in paleoclimatological studies. Over the last several decades, however, researchers have found evidence to suggest that the friction associated with the sampling of biogenic carbonates via milling/drilling also induces inversion. Furthermore, this inversion may be associated with a shift in measured oxygen isotopic values and ultimately have significant implications for the interpretation of paleoclimatic reconstructions. Despite this, the isotopic heterogeneity of biogenic aragonite skeletons makes the effects of inversion challenging to test and the subject remains underrepresented in the literature. Here we present a first order study into the effects of milling on both the mineralogy and isotopic compositions measured in sclerosponges, corals, and molluscs. X-Ray diffraction analysis of samples hand ground with a mortar and pestle reveal 100% aragonitic skeletons. Conversely, samples milled with a computerized micromill show measurable inversion to calcite. On average, percent inversion of aragonite to calcite for individual specimens was 15% for sclerosponges, 16% for corals, and 9% for molluscs. Isotopic data from these specimens show that the higher the percentage of aragonite inverted to calcite, the more depleted the measured oxygen isotopic values. In the largest of the datasets (sclerosponges), it is evident that the range of oxygen isotope values from milled samples (-0.02 to +0.84%) exceeds the range in values for those samples which were hand ground and showed no inversion (+0.53 to +0.90%). This, coupled with the strong correlation between the two variables
Prus, O.; Yaish, Y.; Reznikov, M.; Sivan, U.; Pudalov, V.
2002-01-01
A novel method invented to measure the minute thermodynamic spin magnetization of dilute two dimensional fermions is applied to electrons in a silicon inversion layer. Interplay between the ferromagnetic interaction and disorder enhances the low temperature susceptibility up to 7.5 folds compared with the Pauli susceptibility of non-interacting electrons. The magnetization peaks in the vicinity of the density where transition to strong localization takes place. At the same density, the suscep...
Solving the Axisymmetric Inverse Heat Conduction Problem by a Wavelet Dual Least Squares Method
Directory of Open Access Journals (Sweden)
Fu Chu-Li
2009-01-01
Full Text Available We consider an axisymmetric inverse heat conduction problem of determining the surface temperature from a fixed location inside a cylinder. This problem is ill-posed; the solution (if it exists does not depend continuously on the data. A special project method—dual least squares method generated by the family of Shannon wavelet is applied to formulate regularized solution. Meanwhile, an order optimal error estimate between the approximate solution and exact solution is proved.
Look-up table (LUT) method for inverse halftoning.
Mese, M; Vaidyanathan, P P
2001-01-01
In this paper we propose look-up table (LUT) based methods for inverse halftoning of images. The LUT for inverse halftoning is obtained from the histogram gathered from a few sample halftone images and corresponding original images. The method is extremely fast (no filtering is required) and the PSNR and visual image quality achieved is comparable to the best methods known for inverse halftoning. The LUT inverse halftoning method does not depend on the specific properties of the halftoning method, and can be applied to any halftoning method. Then, an algorithm for template selection for LUT inverse halftoning is introduced. We demonstrate the performance of the LUT inverse halftoning algorithm on error diffused images and ordered dithered images. We also extend LUT inverse halftoning to color halftones.
Inverse Kinematics With Closed Form Solution For Denso Robot Manipulator
Directory of Open Access Journals (Sweden)
Ikhsan Eka Prasetia
2015-03-01
Full Text Available In this paper, the forward kinematics and inverse kinematics used on the Denso robot manipulator which has a 6-DOF. The forward kinematics will result in the desired position by end-effector, while inverse kinematics produce angel on each joint. Inverse kinematics problem are very difficult, therefor to obtain the solution of inverse kinematics using closed form solution with geometry approach. The simulation result obtained from forward kinematics and inverse kinematics is determining desired position by Denso robot manipulator. Forward kinematics produce the desired position by the end-effector. Inverse kinematics produce joint angle, where the inverse kinematics produce eight conditions obtained from closed form solution with geometry approach to reach the desired position by the end-effector.
Dehghan, A.; Mariani, Z.; Gascon, G.; Bélair, S.; Milbrandt, J.; Joe, P. I.; Crawford, R.; Melo, S.
2017-12-01
Environment and Climate Change Canada (ECCC) is implementing a 2.5-km resolution version of the Global Environmental Multiscale (GEM) model over the Canadian Arctic. Radiosonde observations were used to evaluate the numerical representation of surface-based temperature inversion which is a major feature in the Arctic region. Arctic surface-based inversions are often created by imbalance between radiative cooling processes at surface and warm air advection above. This can have a significant effect on vertical mixing of pollutants and moisture, and ultimately, on cloud formation. It is therefore important to correctly predict the existence of surface inversions along with their characteristics (i.e., intensity and depth). Previous climatological studies showed that the frequency and intensity of surface-based inversions are larger during colder months in the Arctic. Therefore, surface-based inversions were estimated using radiosonde measurements during winter (December 2015 to February 2016) at Iqaluit (Nunavut, Canada). Results show that the inversion intensity can exceed 10 K with depths as large as 1 km. Preliminary evaluation of GEM outputs reveals that the model tends to underestimate the intensity of near-surface inversions, and in some cases, the model failed to predict an inversion. This study presents the factors contributing to this bias including surface temperature and snow cover.
Evaluating Ethical Responsibility in Inverse Decision Support
Directory of Open Access Journals (Sweden)
Ahmad M. Kabil
2012-01-01
Full Text Available Decision makers have considerable autonomy on how they make decisions and what type of support they receive. This situation places the DSS analyst in a different relationship with the client than his colleagues who support regular MIS applications. This paper addresses an ethical dilemma in “Inverse Decision Support,” when the analyst supports a decision maker who requires justification for a preconceived selection that does not correspond to the best option that resulted from the professional resolution of the problem. An extended application of the AHP model is proposed for evaluating the ethical responsibility in selecting a suboptimal alternative. The extended application is consistent with the Inverse Decision Theory that is used extensively in medical decision making. A survey of decision analysts is used to assess their perspective of using the proposed extended application. The results show that 80% of the respondents felt that the proposed extended application is useful in business practices. 14% of them expanded the usability of the extended application to academic teaching of the ethics theory. The extended application is considered more usable in a country with a higher Transparency International Corruption Perceptions Index (TICPI than in a country with a lower one.
Approaching the Island of Inversion: 34P
Energy Technology Data Exchange (ETDEWEB)
Bender, P.C.; Hoffman, C.R.; Wiedeking, M.; Allmond, J.M.; Bernstein, L.A.; Burke, J.T.; Bleuel, D.L.; Clark, R.M.; Fallon, P.; Goldblum, B.L.; Hinners, T.A.; Jeppesen, H.B.; Lee, Sangjin; Lee, I.Y.; Lesher, S.R.; Machiavelli, A.O.; McMahan, M.A.; Morris, D.; Perry, M.; Phair, L.; Scielzo, N.D.; Tabor, S.L.; Tripathi, Vandana; Volya, A.
2011-06-14
Yrast states in 34P were investigated using the 18O(18O,pn) reaction at energies of 20, 24, 25, 30, and 44 MeV at Florida State University and at Lawrence Berkeley National Laboratory. The level scheme was expanded, ray angular distributions were measured, and lifetimes were inferred with the Doppler-shift attenuation method by detecting decay protons in coincidence with one or more rays. The results provide a clearer picture of the evolution of structure approaching the 'Island of Inversion', particularly how the 1 and 2 particle-hole (ph) states fall in energy with increasing neutro number approaching inversion. However, the agreement of the lowest few states with pure sd shell model predictions shows that the level scheme of 34P is not itself inverted. Rather, the accumulated evidence indicates that the 1-ph states start at 2.3 MeV. A good candidate for the lowest 2-ph state lies at 6236 keV, just below the neutron separation energy of 6291 keV. Shell model calculations made using a small modification of the WBP interaction reproduce the negative-parity, 1-ph states rather well.
An Entropic Estimator for Linear Inverse Problems
Directory of Open Access Journals (Sweden)
Amos Golan
2012-05-01
Full Text Available In this paper we examine an Information-Theoretic method for solving noisy linear inverse estimation problems which encompasses under a single framework a whole class of estimation methods. Under this framework, the prior information about the unknown parameters (when such information exists, and constraints on the parameters can be incorporated in the statement of the problem. The method builds on the basics of the maximum entropy principle and consists of transforming the original problem into an estimation of a probability density on an appropriate space naturally associated with the statement of the problem. This estimation method is generic in the sense that it provides a framework for analyzing non-normal models, it is easy to implement and is suitable for all types of inverse problems such as small and or ill-conditioned, noisy data. First order approximation, large sample properties and convergence in distribution are developed as well. Analytical examples, statistics for model comparisons and evaluations, that are inherent to this method, are discussed and complemented with explicit examples.
Neutron inverse kinetics via Gaussian Processes
International Nuclear Information System (INIS)
Picca, Paolo; Furfaro, Roberto
2012-01-01
Highlights: ► A novel technique for the interpretation of experiments in ADS is presented. ► The technique is based on Bayesian regression, implemented via Gaussian Processes. ► GPs overcome the limits of classical methods, based on PK approximation. ► Results compares GPs and ANN performance, underlining similarities and differences. - Abstract: The paper introduces the application of Gaussian Processes (GPs) to determine the subcriticality level in accelerator-driven systems (ADSs) through the interpretation of pulsed experiment data. ADSs have peculiar kinetic properties due to their special core design. For this reason, classical – inversion techniques based on point kinetic (PK) generally fail to generate an accurate estimate of reactor subcriticality. Similarly to Artificial Neural Networks (ANNs), Gaussian Processes can be successfully trained to learn the underlying inverse neutron kinetic model and, as such, they are not limited to the model choice. Importantly, GPs are strongly rooted into the Bayes’ theorem which makes them a powerful tool for statistical inference. Here, GPs have been designed and trained on a set of kinetics models (e.g. point kinetics and multi-point kinetics) for homogeneous and heterogeneous settings. The results presented in the paper show that GPs are very efficient and accurate in predicting the reactivity for ADS-like systems. The variance computed via GPs may provide an indication on how to generate additional data as function of the desired accuracy.
Inverse Statistics and Asset Allocation Efficiency
Bolgorian, Meysam
In this paper using inverse statistics analysis, the effect of investment horizon on the efficiency of portfolio selection is examined. Inverse statistics analysis is a general tool also known as probability distribution of exit time that is used for detecting the distribution of the time in which a stochastic process exits from a zone. This analysis was used in Refs. 1 and 2 for studying the financial returns time series. This distribution provides an optimal investment horizon which determines the most likely horizon for gaining a specific return. Using samples of stocks from Tehran Stock Exchange (TSE) as an emerging market and S&P 500 as a developed market, effect of optimal investment horizon in asset allocation is assessed. It is found that taking into account the optimal investment horizon in TSE leads to more efficiency for large size portfolios while for stocks selected from S&P 500, regardless of portfolio size, this strategy does not only not produce more efficient portfolios, but also longer investment horizons provides more efficiency.
Inverse Variational Problem for Nonstandard Lagrangians
Saha, A.; Talukdar, B.
2014-06-01
In the mathematical physics literature the nonstandard Lagrangians (NSLs) were introduced in an ad hoc fashion rather than being derived from the solution of the inverse problem of variational calculus. We begin with the first integral of the equation of motion and solve the associated inverse problem to obtain some of the existing results for NSLs. In addition, we provide a number of alternative Lagrangian representations. The case studies envisaged by us include (i) the usual modified Emden-type equation, (ii) Emden-type equation with dissipative term quadratic in velocity, (iii) Lotka-Volterra model and (vi) a number of the generic equations for dissipative-like dynamical systems. Our method works for nonstandard Lagrangians corresponding to the usual action integral of mechanical systems but requires modification for those associated with the modified actions like S =∫abe L(x ,x˙ , t) dt and S =∫abL 1 - γ(x ,x˙ , t) dt because in the latter case one cannot construct expressions for the Jacobi integrals.
Wave-equation reflection traveltime inversion
Zhang, Sanzong
2011-01-01
The main difficulty with iterative waveform inversion using a gradient optimization method is that it tends to get stuck in local minima associated within the waveform misfit function. This is because the waveform misfit function is highly nonlinear with respect to changes in the velocity model. To reduce this nonlinearity, we present a reflection traveltime tomography method based on the wave equation which enjoys a more quasi-linear relationship between the model and the data. A local crosscorrelation of the windowed downgoing direct wave and the upgoing reflection wave at the image point yields the lag time that maximizes the correlation. This lag time represents the reflection traveltime residual that is back-projected into the earth model to update the velocity in the same way as wave-equation transmission traveltime inversion. No travel-time picking is needed and no high-frequency approximation is assumed. The mathematical derivation and the numerical examples are presented to partly demonstrate its efficiency and robustness. © 2011 Society of Exploration Geophysicists.
Eigenvectors phase correction in inverse modal problem
Qiao, Guandong; Rahmatalla, Salam
2017-12-01
The solution of the inverse modal problem for the spatial parameters of mechanical and structural systems is heavily dependent on the quality of the modal parameters obtained from the experiments. While experimental and environmental noises will always exist during modal testing, the resulting modal parameters are expected to be corrupted with different levels of noise. A novel methodology is presented in this work to mitigate the errors in the eigenvectors when solving the inverse modal problem for the spatial parameters. The phases of the eigenvector component were utilized as design variables within an optimization problem that minimizes the difference between the calculated and experimental transfer functions. The equation of motion in terms of the modal and spatial parameters was used as a constraint in the optimization problem. Constraints that reserve the positive and semi-positive definiteness and the inter-connectivity of the spatial matrices were implemented using semi-definite programming. Numerical examples utilizing noisy eigenvectors with augmented Gaussian white noise of 1%, 5%, and 10% were used to demonstrate the efficacy of the proposed method. The results showed that the proposed method is superior when compared with a known method in the literature.
Inverse Magnetoresistance in Polymer Spin Valves.
Ding, Shuaishuai; Tian, Yuan; Li, Yang; Mi, Wenbo; Dong, Huanli; Zhang, Xiaotao; Hu, Wenping; Zhu, Daoben
2017-05-10
In this work, both negative and positive magnetoresistance (MR) in solution-processed regioregular poly(3-hexylthiophene) (RR-P3HT) is observed in organic spin valves (OSVs) with vertical La 2/3 Sr 1/3 MnO 3 (LSMO)/P3HT/AlO x /Co configuration. The ferromagnetic (FM) LSMO electrode with near-atomic flatness is fabricated by a DC facing-target magnetron sputtering method. This research is focused on the origin of the MR inversion. Two types of devices are investigated in details: One with Co penetration shows a negative MR of 0.2%, while the other well-defined device with a nonlinear behavior has a positive MR of 15.6%. The MR measurements in LSMO/AlO x /Co and LSMO/Co junctions are carried to exclude the interference of insulating layer and two FM electrodes themselves. By examining the Co thicknesses and their corresponding magnetic hysteresis loops, a spin-dependent hybrid-interface-state model by Co penetration is induced to explain the MR sign inversion. These results proven by density functional theory (DFT) calculations may shed light on the controllable interfacial properties in designing novel OSV devices.
Inverse PCR for Point Mutation Introduction.
Silva, Diogo; Santos, Gustavo; Barroca, Mário; Collins, Tony
2017-01-01
Inverse PCR is a powerful tool for the rapid introduction of desired mutations at desired positions in a circular double-stranded DNA sequence. Here, custom-designed mutant primers oriented in the inverse direction are used to amplify the entire circular template with incorporation of the required mutation(s). By careful primer design it can be used to perform such diverse modifications as the introduction of point mutations and multiple mutations, the insertion of new sequences, and even sequence deletions. Three primer formats are commonly used; nonoverlapping, partially overlapping and fully overlapping primers, and here we describe the use of nonoverlapping primers for introduction of a point mutation. Use of such a primer setup in the PCR reaction, with one of the primers containing the desired mismatch mutation, results in the amplification of a linear, double-stranded, mutated product. Methylated template DNA is removed from the nonmethylated PCR product by DpnI digestion and the PCR product is then phosphorylated by polynucleotide kinase treatment before being recircularized by ligation, and transformed to E. coli. This relatively simple site-directed mutagenesis procedure is of major importance in biology and biotechnology today where it is commonly employed for the study and engineering of DNA, RNA, and proteins.
Spectral solution of the inverse Mie problem
Romanov, Andrey V.; Konokhova, Anastasiya I.; Yastrebova, Ekaterina S.; Gilev, Konstantin V.; Strokotov, Dmitry I.; Chernyshev, Andrei V.; Maltsev, Valeri P.; Yurkin, Maxim A.
2017-10-01
We developed a fast method to determine size and refractive index of homogeneous spheres from the power Fourier spectrum of their light-scattering patterns (LSPs), measured with the scanning flow cytometer. Specifically, we used two spectral parameters: the location of the non-zero peak and zero-frequency amplitude, and numerically inverted the map from the space of particle characteristics (size and refractive index) to the space of spectral parameters. The latter parameters can be reliably resolved only for particle size parameter greater than 11, and the inversion is unique only in the limited range of refractive index with upper limit between 1.1 and 1.25 (relative to the medium) depending on the size parameter and particular definition of uniqueness. The developed method was tested on two experimental samples, milk fat globules and spherized red blood cells, and resulted in accuracy not worse than the reference method based on the least-square fit of the LSP with the Mie theory. Moreover, for particles with significant deviation from the spherical shape the spectral method was much closer to the Mie-fit result than the estimated uncertainty of the latter. The spectral method also showed adequate results for synthetic LSPs of spheroids with aspect ratios up to 1.4. Overall, we present a general framework, which can be used to construct an inverse algorithm for any other experimental signals.
Modular inverse reinforcement learning for visuomotor behavior.
Rothkopf, Constantin A; Ballard, Dana H
2013-08-01
In a large variety of situations one would like to have an expressive and accurate model of observed animal or human behavior. While general purpose mathematical models may capture successfully properties of observed behavior, it is desirable to root models in biological facts. Because of ample empirical evidence for reward-based learning in visuomotor tasks, we use a computational model based on the assumption that the observed agent is balancing the costs and benefits of its behavior to meet its goals. This leads to using the framework of reinforcement learning, which additionally provides well-established algorithms for learning of visuomotor task solutions. To quantify the agent's goals as rewards implicit in the observed behavior, we propose to use inverse reinforcement learning, which quantifies the agent's goals as rewards implicit in the observed behavior. Based on the assumption of a modular cognitive architecture, we introduce a modular inverse reinforcement learning algorithm that estimates the relative reward contributions of the component tasks in navigation, consisting of following a path while avoiding obstacles and approaching targets. It is shown how to recover the component reward weights for individual tasks and that variability in observed trajectories can be explained succinctly through behavioral goals. It is demonstrated through simulations that good estimates can be obtained already with modest amounts of observation data, which in turn allows the prediction of behavior in novel configurations.
Applications of Markov random field models for inversion problems in geosciences
Kuwatani, T.; Nagata, K.; Okada, M.; Toriumi, M.
2012-12-01
Recently, a variety of spatial and temporal data sets can be obtained thanks to technological advances of measurement and observation in geosciences. It is very important to inverse spatial or temporal physical variables from these imaging data sets. The Markov random field (MRF) model is a stochastic model using Markov chains that is often applied for image restoration and pattern recognition in information science. In the MRF model, the spatial or temporal variations of physical properties are assumed to be relatively small compared to the observational noise and analytical uncertainty. By the Bayesian approach, the MRF model appropriately filters out high-frequency noise, and we can obtain accurate spatial distributions or time series of physical properties. Furthermore, it has the potential advantage of the incorporation of prior geophysical and geological information through the evaluation function. The purpose of this study is to develop the MRF model in order to apply it to various inversion problems in geosciences. Based on the Bayesian inference, we incorporated the nonlinear generation process of observational data sets into the MRF model. The Markov chain Monte Carlo (MCMC) algorithm was implemented to estimate hyperparameters and optimize target variables. Furthermore, it's important for inversion problems in geosciences to understand discontinuous behavior of physical variables, for example, detection of fault planes and lithospheric boundaries in the earth's interior. By introducing Potts spins as latent variables to the MRF model, we can simultaneously estimate the distributions of continuous and discontinuous variables. For examples of applications, we will introduce two inversion problems: one is a pressure-temperature inversion from compositional data of zoned minerals, and the other is an inversion of fluid distributions from observed seismic velocity structure. Based on these examples, we will discuss effectiveness and broad applicability of the
Methods for joint inversion of waveform and gravity information for 3D density structure
Blom, Nienke; Böhm, Christian; Fichtner, Andreas
2015-04-01
We develop a joint inversion scheme combining seismic waveform and gravity information to better constrain the Earth's 3D density distribution. Our inversion schemes are based on numerical wave propagation, adjoint techniques, gravity and other non-seismological constraints to enhance resolution. Density variations drive convection in the Earth and serve as a discriminator between thermal and compositional heterogeneities. However, classical seismological observables are only very weakly sensitive to density with significant trade-offs, while potential field measurements such as gravity suffer from inherent non-uniqueness. To put additional constraints on density structure, we develop inversion schemes in which the waveform and gravity data are inverted jointly for both density and seismic velocity parameters. Our inversion scheme is intended to incorporate any information that can help to constrain 3D density structure. This includes gravity-derived quantities such as the mass and moment of inertia of the Earth, but also mineral physical constraints on maximum density heterogeneities (assuming reasonable variations in temperature and composition). In a series of initial synthetic experiments, we aim to construct efficient optimisation schemes that allow us to assimilate all the available types of information. For this, we use 2D numerical wave propagation combined with adjoint techniques for the computation of sensitivity kernels. With these kernels, we drive gradient-based optimisation that incorporates our non-seismological constraints. Specifically, we assess the usefulness of an inversion scheme where the Earth's mass and moment of inertia are enforced in the model by means of a projected gradient scheme. These synthetic experiments will allow us to assess to what extent velocity and density structure need to be coupled in order to obtain useful and meaningful results to a density inversion.
Inverse modeling of April 2013 radioxenon detections
Hofman, Radek; Seibert, Petra; Philipp, Anne
2014-05-01
Significant concentrations of radioactive xenon isotopes (radioxenon) were detected by the International Monitoring System (IMS) for verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in April 2013 in Japan. Particularly, three detections of Xe-133 made between 2013-04-07 18:00 UTC and 2013-04-09 06:00 UTC at the station JPX38 are quite notable with respect to the measurement history of the station. Our goal is to analyze the data and perform inverse modeling under different assumptions. This work is useful with respect to nuclear test monitoring as well as for the analysis of and response to nuclear emergencies. Two main scenarios will be pursued: (i) Source location is assumed to be known (DPRK test site). (ii) Source location is considered unknown. We attempt to estimate the source strength and the source strength along with its plausible location compatible with the data in scenario (i) and (ii), respectively. We are considering also the possibility of a vertically distributed source. Calculations of source-receptor sensitivity (SRS) fields and the subsequent inversion are aimed at going beyond routine calculations performed by the CTBTO. For SRS calculations, we employ the Lagrangian particle dispersion model FLEXPART with high resolution ECMWF meteorological data (grid cell sizes of 0.5, 0.25 and ca. 0.125 deg). This is important in situations where receptors or sources are located in complex terrain which is the case of the likely source of detections-the DPRK test site. SRS will be calculated with convection enabled in FLEXPART which will also increase model accuracy. In the variational inversion procedure attention will be paid not only to all significant detections and their uncertainties but also to non-detections which can have a large impact on inversion quality. We try to develop and implement an objective algorithm for inclusion of relevant data where samples from temporal and spatial vicinity of significant detections are added in an
A low temperature neutron diffraction study of manganese ferrite
International Nuclear Information System (INIS)
Jirak, Z.; Zajicek, J.
1978-01-01
Two specimens of the Mnsub(0.98)Fesub(2.02)Osub(4+0.002) monocrystal differing in the degree of inversion and heat treatment were studied at room temperature and at the liquid helium temperature, respectively. The specimen with the lower inversion degree was heated to 600 degC and subsequently slowly cooled to 340 degC and annealed for 50 hrs; the specimen with the higher inversion degree was quenched from a temperature of 600 degC. In the study, the magnetic moments on sites A and B of the spinel lattice, the degree of inversion, the oxygen parameter and the Debye-Waller factor were investigated. The oxygen parameter was found to be higher at both temperatures for the annealed specimen (with the lower inversion degree), which can be attributed to the inversion degree dependence of the Madelung energy and the mean ion radius on sites A and B. The oxygen parameter did not show significant differences at room and liquid helium temperature. This agrees with the assumption that it is temperature-independent. (J.P.)
Optimal Inversion Parameters for Full Waveform Inversion using OBS Data Set
Kim, S.; Chung, W.; Shin, S.; Kim, D.; Lee, D.
2017-12-01
In recent years, full Waveform Inversion (FWI) has been the most researched technique in seismic data processing. It uses the residuals between observed and modeled data as an objective function; thereafter, the final subsurface velocity model is generated through a series of iterations meant to minimize the residuals.Research on FWI has expanded from acoustic media to elastic media. In acoustic media, the subsurface property is defined by P-velocity; however, in elastic media, properties are defined by multiple parameters, such as P-velocity, S-velocity, and density. Further, the elastic media can also be defined by Lamé constants, density or impedance PI, SI; consequently, research is being carried out to ascertain the optimal parameters.From results of advanced exploration equipment and Ocean Bottom Seismic (OBS) survey, it is now possible to obtain multi-component seismic data. However, to perform FWI on these data and generate an accurate subsurface model, it is important to determine optimal inversion parameters among (Vp, Vs, ρ), (λ, μ, ρ), and (PI, SI) in elastic media. In this study, staggered grid finite difference method was applied to simulate OBS survey. As in inversion, l2-norm was set as objective function. Further, the accurate computation of gradient direction was performed using the back-propagation technique and its scaling was done using the Pseudo-hessian matrix.In acoustic media, only Vp is used as the inversion parameter. In contrast, various sets of parameters, such as (Vp, Vs, ρ) and (λ, μ, ρ) can be used to define inversion in elastic media. Therefore, it is important to ascertain the parameter that gives the most accurate result for inversion with OBS data set.In this study, we generated Vp and Vs subsurface models by using (λ, μ, ρ) and (Vp, Vs, ρ) as inversion parameters in every iteration, and compared the final two FWI results.This research was supported by the Basic Research Project(17-3312) of the Korea Institute of
ORINC: a one-dimensional implicit approach to the inverse heat conduction problem. [PWR
Energy Technology Data Exchange (ETDEWEB)
Ott, L.J.; Hedrick, R.A.
1977-10-18
The report develops an implicit solution technique to determine both the transient surface temperature and the transient surface heat flux of electrically heated rods given the power input and an ''indicated'' internal temperature during a simulated loss-of-coolant accident. A digital computer program ORINC (ORNL Inverse Code) is developed which solves a one-dimensional, transient, lumped parameter, implicit formulation of the conduction equation at each bundle thermocouple position in the Thermal-Hydraulic Test Facility (THTF).
Bilinear Inverse Problems: Theory, Algorithms, and Applications
Ling, Shuyang
We will discuss how several important real-world signal processing problems, such as self-calibration and blind deconvolution, can be modeled as bilinear inverse problems and solved by convex and nonconvex optimization approaches. In Chapter 2, we bring together three seemingly unrelated concepts, self-calibration, compressive sensing and biconvex optimization. We show how several self-calibration problems can be treated efficiently within the framework of biconvex compressive sensing via a new method called SparseLift. More specifically, we consider a linear system of equations y = DAx, where the diagonal matrix D (which models the calibration error) is unknown and x is an unknown sparse signal. By "lifting" this biconvex inverse problem and exploiting sparsity in this model, we derive explicit theoretical guarantees under which both x and D can be recovered exactly, robustly, and numerically efficiently. In Chapter 3, we study the question of the joint blind deconvolution and blind demixing, i.e., extracting a sequence of functions [special characters omitted] from observing only the sum of their convolutions [special characters omitted]. In particular, for the special case s = 1, it becomes the well-known blind deconvolution problem. We present a non-convex algorithm which guarantees exact recovery under conditions that are competitive with convex optimization methods, with the additional advantage of being computationally much more efficient. We discuss several applications of the proposed framework in image processing and wireless communications in connection with the Internet-of-Things. In Chapter 4, we consider three different self-calibration models of practical relevance. We show how their corresponding bilinear inverse problems can be solved by both the simple linear least squares approach and the SVD-based approach. As a consequence, the proposed algorithms are numerically extremely efficient, thus allowing for real-time deployment. Explicit theoretical
Nonlinear Spatial Inversion Without Monte Carlo Sampling
Curtis, A.; Nawaz, A.
2017-12-01
High-dimensional, nonlinear inverse or inference problems usually have non-unique solutions. The distribution of solutions are described by probability distributions, and these are usually found using Monte Carlo (MC) sampling methods. These take pseudo-random samples of models in parameter space, calculate the probability of each sample given available data and other information, and thus map out high or low probability values of model parameters. However, such methods would converge to the solution only as the number of samples tends to infinity; in practice, MC is found to be slow to converge, convergence is not guaranteed to be achieved in finite time, and detection of convergence requires the use of subjective criteria. We propose a method for Bayesian inversion of categorical variables such as geological facies or rock types in spatial problems, which requires no sampling at all. The method uses a 2-D Hidden Markov Model over a grid of cells, where observations represent localized data constraining the model in each cell. The data in our example application are seismic properties such as P- and S-wave impedances or rock density; our model parameters are the hidden states and represent the geological rock types in each cell. The observations at each location are assumed to depend on the facies at that location only - an assumption referred to as `localized likelihoods'. However, the facies at a location cannot be determined solely by the observation at that location as it also depends on prior information concerning its correlation with the spatial distribution of facies elsewhere. Such prior information is included in the inversion in the form of a training image which represents a conceptual depiction of the distribution of local geologies that might be expected, but other forms of prior information can be used in the method as desired. The method provides direct (pseudo-analytic) estimates of posterior marginal probability distributions over each variable
Experimental characterization of methane inverse diffusion flame
Elbaz, Ayman M.
2014-06-26
This article presents 10-kHz images of OH-PLIF simultaneously with 2-D PIV measurements in an inverse methane diffusion flame. Under a constant fuel flow rate, the central air jet Re was varied, leading to air to fuel velocity ratio, Vr, to vary from 8.3 to 66.5. Starting from Vr = 20.7, the flame is commonly characterized by three distinct zones. The length of the lower fuel entrainment region is inversely proportional to Vr. The flames investigated resemble a string shear layer confining this zone, and converging into the second distinct region, the flame neck zone. The third region is the rest of the flame, which spreads in a jet-like manner. The inverse diffusion flames exhibit varying degrees of partial premixing, depending upon on the velocity ratio Vr, and this region of partial premixing evolves into a well-mixed reaction zone along the flame centerline. The OH distribution correlated with the changes in the mean characteristics of the flow through reduction in the local Reynolds number due to heat release. The existence of a flame suppresses or laminarizes the turbulence at early axial locations and promotes fluctuations at the flame tip for flames with Vr < 49.8. In addition, the flame jet width can be correlated to the OH distribution. In upstream regions of the flames, the breaks in OH are counterbalanced by flame closures and are governed by edge flame propagation. These local extinctions were found to occur at locations where large flow structures were impinging on the flame and are associated with a locally higher strain rate or correlated to the local high strain rates at the flame hole edges without this flow impinging. Another contributor to re-ignition was found to be growing flame kernels. As the flames approach global blow-off, these kernels become the main mechanism for re-ignition further downstream of the flames. At low Vr, laminarization within the early regions of the flame provides an effective shield, preventing the jet flow from
Inversion of the uterus following abortion.
Gupta, A S; Datta, N; Ghosh, D
1982-10-16
A case of inversion of the uterus following abortion is reported. The 35-year old patient, admitted October 10, 1978 to the Medical College and Hospitals in Calcutta, India was referred by a private practitioner with a history of amenorrhea for 16 weeks, bleeding for 3 days, expulsion of the fetus 3 days earlier, and something coming down per vaginum for 2 days. The patient was para 4+0 (all full term normal deliveries) and home delivery for the last child 1 1/2 years earlier. She had a history of regular menstrual periods. Her general condition was poor. The examination revealed a gangrenous mass coming out of the vulva with a very offensive smell. There was a raw surface on which placenta like tissue was attached. No active bleeding was seen. Fundus and cervix of the uterus could not be felt. On rectal examination the uterus could not be felt, a cup-like depression was felt at the site of the uterus. The provision diagnosis was inversion of uterus following abortion. Treatment was started with sedatives and antibiotics, and arrangements were made for a blood transfusion. The vaginal mass was covered with glycerine and acriflavine gauze, and a hysterectomy was decided upon after improvement of her general condition and control of the infection. On October 14th, the patient was placed in knee chest position and posterior vaginal wall was retracted with Sims' speculum when the inverted lump was spontaneously reduced within the vagina. The inverted uterus was felt in the region of the vaginal vault. Glycerine acriflavine pack was given which was taken out and repack was given daily until the operation. The hysterectomy was performed on October 23rd. The abdomen was opened up by a transverse incision and the pelvis was explored. In the region of the uterus a cup-shaped depression was noted. Tubes and ovaries of both sides were seen hanging laterally from the cupped area. The left tube was found congested and thickened. Reduction of uterus was done by making a vertical
Inverse and normal magnetocaloric effects in LaFe12B6
International Nuclear Information System (INIS)
Diop, L. V. B.; Isnard, O.
2016-01-01
Intrinsic magnetic properties and magnetocaloric effect were studied for LaFe 12 B 6 itinerant-electron system, which presents an antiferromagnetic ground state below 36 K. For certain magnetic fields values, LaFe 12 B 6 exhibits a sequence of two successive magnetic transitions: an antiferromagnetic-ferromagnetic (AFM-FM) transition at low temperature followed by a ferromagnetic-paramagnetic transition, leading to normal and inverse magnetocaloric effects, respectively. At finite temperatures, both antiferromagnetic (AFM) and paramagnetic states can be transformed into a ferromagnetic (FM) state via a field-induced metamagnetic transition accompanied with a huge magnetic hysteresis. Moreover, we reveal that, at low temperatures, the magnetization displays abrupt jumps across the first-order AFM-FM transition, giving rise to an unusual and unique staircase-like behavior. LaFe 12 B 6 exhibits both normal magnetocaloric effect around the Curie temperature and large inverse magnetocaloric effect around the AFM-FM transition temperature; for μ 0 ΔH = 7 T, ΔS M is found to be −6.8 and 19 J kg −1 K −1 around 38 and 8 K, respectively.
On the quantum inverse scattering problem
International Nuclear Information System (INIS)
Maillet, J.M.; Terras, V.
2000-01-01
A general method for solving the so-called quantum inverse scattering problem (namely the reconstruction of local quantum (field) operators in term of the quantum monodromy matrix satisfying a Yang-Baxter quadratic algebra governed by an R-matrix) for a large class of lattice quantum integrable models is given. The principal requirement being the initial condition (R(0)=P, the permutation operator) for the quantum R-matrix solving the Yang-Baxter equation, it applies not only to most known integrable fundamental lattice models (such as Heisenberg spin chains) but also to lattice models with arbitrary number of impurities and to the so-called fused lattice models (including integrable higher spin generalizations of Heisenberg chains). Our method is then applied to several important examples like the sl n XXZ model, the XYZ spin-((1)/(2)) chain and also to the spin-s Heisenberg chains
Inverse eigenvalue problems for semilinear elliptic equations
Directory of Open Access Journals (Sweden)
Tetsutaro Shibata
2009-09-01
Full Text Available We consider the inverse nonlinear eigenvalue problem for the equation $$displaylines{ -Delta u + f(u = lambda u, quad u > 0 quad hbox{in } Omega,cr u = 0 quad hbox{on } partialOmega, } where $f(u$ is an unknown nonlinear term, $Omega subset mathbb{R}^N$ is a bounded domain with an appropriate smooth boundary $partialOmega$ and $lambda > 0$ is a parameter. Under basic conditions on $f$, for any given $alpha > 0$, there exists a unique solution $(lambda, u = (lambda(alpha, u_alpha in mathbb{R}_+ imes C^2(ar{Omega}$ with $|u_alpha|_2 = alpha$. The curve $lambda(alpha$ is called the $L^2$-bifurcation branch. Using a variational approach, we show that the nonlinear term $f(u$ is determined uniquely by $lambda(alpha$.
Multipass optical cavity for inverse Compton interactions
Energy Technology Data Exchange (ETDEWEB)
Rollason, A.J. E-mail: a.j.rollason@keele.ac.uk; Fang, X.; Dugdale, D.E
2004-07-01
The recycling of laser beams in the focal region of non-resonant multipass optical cavities has been investigated as a means of providing a high intensity of photons for weak interaction experiments. Ray-tracing simulations and measurements with an Ar-ion laser have been carried out to examine the intensity profiles of the laser field in different 2-mirror geometries. In particular, the use of such cavities in the generation of X-rays by inverse Compton scattering is considered. X-ray yields are calculated for electron beams of 0.05, 0.1, 0.2 and 0.5 mm diameter yielding enhancement factors of 10-200 compared to a free space laser interaction.
Intermediate simulation of the inverse seismic problem
International Nuclear Information System (INIS)
Brolley, J.E.
1980-03-01
An introductory study of the inverse seismic problem is performed. The complex cepstrum of a seismogram generated by the convolution of three factors, the Seggern-Blandford source function of an explosion, the Futterman mantle transfer function, and the SRO seismometer transfer function, is used. For a given Q and yield, a synthetic seismogram is computed. Arbitrary values of Q and yield are introduced, and a search is conducted to find that pair of values that minimized the cepstral difference between the original and arbitrary seismograms. The original values are accurately recovered. Spectral and amplitude characteristics of the various factors are presented. Possible application to the problem of studying a medium intervening between a source and receiver is discussed. 25 figures, 1 table
Inverse problems for partial differential equations
Isakov, Victor
2017-01-01
This third edition expands upon the earlier edition by adding nearly 40 pages of new material reflecting the analytical and numerical progress in inverse problems in last 10 years. As in the second edition, the emphasis is on new ideas and methods rather than technical improvements. These new ideas include use of the stationary phase method in the two-dimensional elliptic problems and of multi frequencies\\temporal data to improve stability and numerical resolution. There are also numerous corrections and improvements of the exposition throughout. This book is intended for mathematicians working with partial differential equations and their applications, physicists, geophysicists, and financial, electrical, and mechanical engineers involved with nondestructive evaluation, seismic exploration, remote sensing, and various kinds of tomography. Review of the second edition: "The first edition of this excellent book appeared in 1998 and became a standard reference for everyone interested in analysis and numerics of...
Remarks on inverse scattering in one dimension
Newton, Roger G.
1984-10-01
This paper answers the following questions: (1) what are the consequences in the matrix-Marchenko inversion scheme if a given S matrix lacks forward analyticity; and (2) in particular, does the condition known as the miracle depend on forward analyticity, and if not, what properties of S does it depend on? The answers are (1) if the input S matrix lacks forward analyticity then the output S matrix has it anyway, and (2) integrability of kRl,r is sufficient for the miracle to occur. It is also found that the matrix-Marchenko procedure simultaneously constructs the potentials for two scattering problems which differ only by the signs of their reflection coefficients.
Hybrid methods of seismic data inversion
Katz, Simon; Beylin, Alex
1993-12-01
A new hybrid method for inversion of reflected seismic waves based on iterative minimization of a cost function has been developed and tested on synthetic data. It includes the following steps: (1) iterative generation of a trial set of wave-forms, (2) construction of the fuzzy neighborhood set for a recorded wave-form in the set of trial wave-forms, (3) fuzzy mapping of the neighborhood set to the space of seismic parameters to produce the fuzzy image of the neighborhood set, and (4) defuzzification of the image set and calculation of the center of the next set of trial wave-forms. The sequence of centers of the trial wave-forms is constructed in such a way that it converges to a global minimum of the cost function.
Directed Neutron Beams From Inverse Kinematic Reactions
Vanhoy, J. R.; Guardala, N. A.; Glass, G. A.
2011-06-01
Kinematic focusing of an emitted fairly mono-energetic neutron beam by the use of inverse-kinematic reactions, i.e. where the projectile mass is greater than the target atom's mass, can provide for the utilization of a significant fraction of the fast neutron yield and also provide for a safer radiation environment. We examine the merit of various neutron production reactions and consider the practicalities of producing the primary beam using the suitable accelerator technologies. Preliminary progress at the NSWC-Carderock Positive Ion Accelerator Facility is described. Possible important applications for this type of neutron-based system can be both advanced medical imaging techniques and active "stand-off" interrogation of contraband items.
Producing a steady-state population inversion
International Nuclear Information System (INIS)
Richards, R.K.; Griffin, D.C.
1986-03-01
An observed steady-state transition at 17.5 nm is identified as the 2p 5 3s3p 4 S/sub 3/2/ → 2p 6 3p 2 P/sub 3/2/ transition in Na-like aluminum. The upper level is populated by electron inner shell ionization of metastable Mg-like aluminum. From the emission intensity, the rate coefficient for populating the upper level is calculated to be approximately 5 x 10 -10 ) cm 3 /sec. Since the upper level is quasimetastable with a lifetime 22 times longer than the lower level, it may be possible to produce a population inversion, if a competing process to populate the lower level can be reduced
Incomplete Sparse Approximate Inverses for Parallel Preconditioning
International Nuclear Information System (INIS)
Anzt, Hartwig; University of Tennessee, Knoxville, TN; Huckle, Thomas K.; Bräckle, Jürgen; Dongarra, Jack
2017-01-01
In this study, we propose a new preconditioning method that can be seen as a generalization of block-Jacobi methods, or as a simplification of the sparse approximate inverse (SAI) preconditioners. The “Incomplete Sparse Approximate Inverses” (ISAI) is in particular efficient in the solution of sparse triangular linear systems of equations. Those arise, for example, in the context of incomplete factorization preconditioning. ISAI preconditioners can be generated via an algorithm providing fine-grained parallelism, which makes them attractive for hardware with a high concurrency level. Finally, in a study covering a large number of matrices, we identify the ISAI preconditioner as an attractive alternative to exact triangular solves in the context of incomplete factorization preconditioning.
Numerical Methods for Bayesian Inverse Problems
Ernst, Oliver
2014-01-06
We present recent results on Bayesian inversion for a groundwater flow problem with an uncertain conductivity field. In particular, we show how direct and indirect measurements can be used to obtain a stochastic model for the unknown. The main tool here is Bayes’ theorem which merges the indirect data with the stochastic prior model for the conductivity field obtained by the direct measurements. Further, we demonstrate how the resulting posterior distribution of the quantity of interest, in this case travel times of radionuclide contaminants, can be obtained by Markov Chain Monte Carlo (MCMC) simulations. Moreover, we investigate new, promising MCMC methods which exploit geometrical features of the posterior and which are suited to infinite dimensions.
Confidence bands for inverse regression models
International Nuclear Information System (INIS)
Birke, Melanie; Bissantz, Nicolai; Holzmann, Hajo
2010-01-01
We construct uniform confidence bands for the regression function in inverse, homoscedastic regression models with convolution-type operators. Here, the convolution is between two non-periodic functions on the whole real line rather than between two periodic functions on a compact interval, since the former situation arguably arises more often in applications. First, following Bickel and Rosenblatt (1973 Ann. Stat. 1 1071–95) we construct asymptotic confidence bands which are based on strong approximations and on a limit theorem for the supremum of a stationary Gaussian process. Further, we propose bootstrap confidence bands based on the residual bootstrap and prove consistency of the bootstrap procedure. A simulation study shows that the bootstrap confidence bands perform reasonably well for moderate sample sizes. Finally, we apply our method to data from a gel electrophoresis experiment with genetically engineered neuronal receptor subunits incubated with rat brain extract
The inverse problem for Schwinger pair production
Directory of Open Access Journals (Sweden)
F. Hebenstreit
2016-02-01
Full Text Available The production of electron–positron pairs in time-dependent electric fields (Schwinger mechanism depends non-linearly on the applied field profile. Accordingly, the resulting momentum spectrum is extremely sensitive to small variations of the field parameters. Owing to this non-linear dependence it is so far unpredictable how to choose a field configuration such that a predetermined momentum distribution is generated. We show that quantum kinetic theory along with optimal control theory can be used to approximately solve this inverse problem for Schwinger pair production. We exemplify this by studying the superposition of a small number of harmonic components resulting in predetermined signatures in the asymptotic momentum spectrum. In the long run, our results could facilitate the observation of this yet unobserved pair production mechanism in quantum electrodynamics by providing suggestions for tailored field configurations.
Inverse Tunnel Magnetocapacitance in Fe/Al-oxide/Fe3O4.
Kaiju, Hideo; Nagahama, Taro; Sasaki, Shun; Shimada, Toshihiro; Kitakami, Osamu; Misawa, Takahiro; Fujioka, Masaya; Nishii, Junji; Xiao, Gang
2017-06-01
Magnetocapacitance (MC) effect, observed in a wide range of materials and devices, such as multiferroic materials and spintronic devices, has received considerable attention due to its interesting physical properties and practical applications. A normal MC effect exhibits a higher capacitance when spins in the electrodes are parallel to each other and a lower capacitance when spins are antiparallel. Here we report an inverse tunnel magnetocapacitance (TMC) effect for the first time in Fe/AlO x /Fe 3 O 4 magnetic tunnel junctions (MTJs). The inverse TMC reaches up to 11.4% at room temperature and the robustness of spin polarization is revealed in the bias dependence of the inverse TMC. Excellent agreement between theory and experiment is achieved for the entire applied frequency range and the wide bipolar bias regions using Debye-Fröhlich model (combined with the Zhang formula and parabolic barrier approximation) and spin-dependent drift-diffusion model. Furthermore, our theoretical calculations predict that the inverse TMC effect could potentially reach 150% in MTJs with a positive and negative spin polarization of 65% and -42%, respectively. These theoretical and experimental findings provide a new insight into both static and dynamic spin-dependent transports. They will open up broader opportunities for device applications, such as magnetic logic circuits and multi-valued memory devices.
Direct Waveform Inversion: a New Recursive Scheme
Zheng, Y.
2015-12-01
The goal of the full-waveform inversion (FWI) is to find an Earth's model such that the synthetic waveforms computed using the model fit the observed ones. In practice, such a model is found in the context of the perturbation approach in an iterative fashion. Specifically, to find such a model, one starts from an initial global velocity model and perform model updating iteratively based on the Frechet derivative or single scattering by adjoint methods to minimize some cost function. However, this process often leads to local minima for the nonlinear cost function in the optimization and slow or no convergence when the starting model is far from the true model. To solve for the initial-model dependence and the convergence issue, we show a new direct waveform inversion (DWI) idea to directly invert the waveform data recursively by explicitly enforcing the causality principle. The DWI offers the advantage of assuming no global initial model and no iteration is needed for the model updating. Starting from the source-receiver region, the DWI builds the model outward recursively by fitting the earliest part of the reflection waveforms and the DWI process is always convergent. The DWI combines seismic imaging and velocity model building into one single process and this is in contrast to many industrial applications where seismic imaging/migration and velocity modeling building are done alternatively. The DWI idea is applicable to one-, two-, and three-dimensional spaces. We show numerical examples to support our idea using full waveform data including both free-surface and inter-bed multiples. Using reflection seismic data, we show that the DWI can invert for both velocity and density, separately.
The inverse gravimetric problem in gravity modelling
Sanso, F.; Tscherning, C. C.
1989-01-01
One of the main purposes of geodesy is to determine the gravity field of the Earth in the space outside its physical surface. This purpose can be pursued without any particular knowledge of the internal density even if the exact shape of the physical surface of the Earth is not known, though this seems to entangle the two domains, as it was in the old Stoke's theory before the appearance of Molodensky's approach. Nevertheless, even when large, dense and homogeneous data sets are available, it was always recognized that subtracting from the gravity field the effect of the outer layer of the masses (topographic effect) yields a much smoother field. This is obviously more important when a sparse data set is bad so that any smoothing of the gravity field helps in interpolating between the data without raising the modeling error, this approach is generally followed because it has become very cheap in terms of computing time since the appearance of spectral techniques. The mathematical description of the Inverse Gravimetric Problem (IGP) is dominated mainly by two principles, which in loose terms can be formulated as follows: the knowledge of the external gravity field determines mainly the lateral variations of the density; and the deeper the density anomaly giving rise to a gravity anomaly, the more improperly posed is the problem of recovering the former from the latter. The statistical relation between rho and n (and its inverse) is also investigated in its general form, proving that degree cross-covariances have to be introduced to describe the behavior of rho. The problem of the simultaneous estimate of a spherical anomalous potential and of the external, topographic masses is addressed criticizing the choice of the mixed collection approach.
Stochastic inverse problems: Models and metrics
International Nuclear Information System (INIS)
Sabbagh, Elias H.; Sabbagh, Harold A.; Murphy, R. Kim; Aldrin, John C.; Annis, Charles; Knopp, Jeremy S.
2015-01-01
In past work, we introduced model-based inverse methods, and applied them to problems in which the anomaly could be reasonably modeled by simple canonical shapes, such as rectangular solids. In these cases the parameters to be inverted would be length, width and height, as well as the occasional probe lift-off or rotation. We are now developing a formulation that allows more flexibility in modeling complex flaws. The idea consists of expanding the flaw in a sequence of basis functions, and then solving for the expansion coefficients of this sequence, which are modeled as independent random variables, uniformly distributed over their range of values. There are a number of applications of such modeling: 1. Connected cracks and multiple half-moons, which we have noted in a POD set. Ideally we would like to distinguish connected cracks from one long shallow crack. 2. Cracks of irregular profile and shape which have appeared in cold work holes during bolt-hole eddy-current inspection. One side of such cracks is much deeper than other. 3. L or C shaped crack profiles at the surface, examples of which have been seen in bolt-hole cracks. By formulating problems in a stochastic sense, we are able to leverage the stochastic global optimization algorithms in NLSE, which is resident in VIC-3D®, to answer questions of global minimization and to compute confidence bounds using the sensitivity coefficient that we get from NLSE. We will also address the issue of surrogate functions which are used during the inversion process, and how they contribute to the quality of the estimation of the bounds
Stochastic inverse problems: Models and metrics
Sabbagh, Elias H.; Sabbagh, Harold A.; Murphy, R. Kim; Aldrin, John C.; Annis, Charles; Knopp, Jeremy S.
2015-03-01
In past work, we introduced model-based inverse methods, and applied them to problems in which the anomaly could be reasonably modeled by simple canonical shapes, such as rectangular solids. In these cases the parameters to be inverted would be length, width and height, as well as the occasional probe lift-off or rotation. We are now developing a formulation that allows more flexibility in modeling complex flaws. The idea consists of expanding the flaw in a sequence of basis functions, and then solving for the expansion coefficients of this sequence, which are modeled as independent random variables, uniformly distributed over their range of values. There are a number of applications of such modeling: 1. Connected cracks and multiple half-moons, which we have noted in a POD set. Ideally we would like to distinguish connected cracks from one long shallow crack. 2. Cracks of irregular profile and shape which have appeared in cold work holes during bolt-hole eddy-current inspection. One side of such cracks is much deeper than other. 3. L or C shaped crack profiles at the surface, examples of which have been seen in bolt-hole cracks. By formulating problems in a stochastic sense, we are able to leverage the stochastic global optimization algorithms in NLSE, which is resident in VIC-3D®, to answer questions of global minimization and to compute confidence bounds using the sensitivity coefficient that we get from NLSE. We will also address the issue of surrogate functions which are used during the inversion process, and how they contribute to the quality of the estimation of the bounds.
Full waveform inversion of solar interior flows
Energy Technology Data Exchange (ETDEWEB)
Hanasoge, Shravan M. [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai 400005 (India)
2014-12-10
The inference of flows of material in the interior of the Sun is a subject of major interest in helioseismology. Here, we apply techniques of full waveform inversion (FWI) to synthetic data to test flow inversions. In this idealized setup, we do not model seismic realization noise, training the focus entirely on the problem of whether a chosen supergranulation flow model can be seismically recovered. We define the misfit functional as a sum of L {sub 2} norm deviations in travel times between prediction and observation, as measured using short-distance filtered f and p {sub 1} and large-distance unfiltered p modes. FWI allows for the introduction of measurements of choice and iteratively improving the background model, while monitoring the evolution of the misfit in all desired categories. Although the misfit is seen to uniformly reduce in all categories, convergence to the true model is very slow, possibly because it is trapped in a local minimum. The primary source of error is inaccurate depth localization, which, due to density stratification, leads to wrong ratios of horizontal and vertical flow velocities ({sup c}ross talk{sup )}. In the present formulation, the lack of sufficient temporal frequency and spatial resolution makes it difficult to accurately localize flow profiles at depth. We therefore suggest that the most efficient way to discover the global minimum is to perform a probabilistic forward search, involving calculating the misfit associated with a broad range of models (generated, for instance, by a Monte Carlo algorithm) and locating the deepest minimum. Such techniques possess the added advantage of being able to quantify model uncertainty as well as realization noise (data uncertainty).
Neural learning of robot inverse kinematics transformations
Gupta, M. M.
1994-06-01
The accuracy of a robot arm is determined by its ability to move in a given particular task space to specific Cartesian positions that are not necessarily pretaught. As a consequence, the inverse kinematics is an important problem as it must be solved in real-time in order to position the end-effector at an appropriate Cartesian location. However, it is a difficult and challenging problem for it involves the determination whether or not at least one mathematical set of robot joint angle values exists that will produce a desired coordinate configuration. The mathematical solutions should be checked against the physical constraints associated with the manipulator. Many times, a solution many not be physically realizable in a constrained environment. The advent of artificial neural networks has made it possible to obtain general learning schemes which can be used to arrive at feasible solutions to inverse kinematics problem in a constrained environment independent of a robotic structure. In this paper, we present such a learning scheme using a dynamic neural processor (DNP). This neural model functionally mimics the subpopulation of biological neurons. For analytical simplicity, only two subpopulations of neurons, namely excitatory and inhibitory, are assumed to coexist. The DNP is a neural network structure consisting of two dynamic neural units coupled as excitatory and inhibitory neurons. It is demonstrated in this study that the DNP would avoid time consuming numerical calculations and provide, more or less, instant recall of the learned associations. The learning and adaptive nature of this neural approach is demonstrated for two- and three-linked robots.
Sensitivity analysis of distributed volcanic source inversion
Cannavo', Flavio; Camacho, Antonio G.; González, Pablo J.; Puglisi, Giuseppe; Fernández, José
2016-04-01
A recently proposed algorithm (Camacho et al., 2011) claims to rapidly estimate magmatic sources from surface geodetic data without any a priori assumption about source geometry. The algorithm takes the advantages of fast calculation from the analytical models and adds the capability to model free-shape distributed sources. Assuming homogenous elastic conditions, the approach can determine general geometrical configurations of pressured and/or density source and/or sliding structures corresponding to prescribed values of anomalous density, pressure and slip. These source bodies are described as aggregation of elemental point sources for pressure, density and slip, and they fit the whole data (keeping some 3D regularity conditions). Although some examples and applications have been already presented to demonstrate the ability of the algorithm in reconstructing a magma pressure source (e.g. Camacho et al., 2011,Cannavò et al., 2015), a systematic analysis of sensitivity and reliability of the algorithm is still lacking. In this explorative work we present results from a large statistical test designed to evaluate the advantages and limitations of the methodology by assessing its sensitivity to the free and constrained parameters involved in inversions. In particular, besides the source parameters, we focused on the ground deformation network topology, and noise in measurements. The proposed analysis can be used for a better interpretation of the algorithm results in real-case applications. Camacho, A. G., González, P. J., Fernández, J. & Berrino, G. (2011) Simultaneous inversion of surface deformation and gravity changes by means of extended bodies with a free geometry: Application to deforming calderas. J. Geophys. Res. 116. Cannavò F., Camacho A.G., González P.J., Mattia M., Puglisi G., Fernández J. (2015) Real Time Tracking of Magmatic Intrusions by means of Ground Deformation Modeling during Volcanic Crises, Scientific Reports, 5 (10970) doi:10.1038/srep
Advances in Global Full Waveform Inversion
Tromp, J.; Bozdag, E.; Lei, W.; Ruan, Y.; Lefebvre, M. P.; Modrak, R. T.; Orsvuran, R.; Smith, J. A.; Komatitsch, D.; Peter, D. B.
2017-12-01
Information about Earth's interior comes from seismograms recorded at its surface. Seismic imaging based on spectral-element and adjoint methods has enabled assimilation of this information for the construction of 3D (an)elastic Earth models. These methods account for the physics of wave excitation and propagation by numerically solving the equations of motion, and require the execution of complex computational procedures that challenge the most advanced high-performance computing systems. Current research is petascale; future research will require exascale capabilities. The inverse problem consists of reconstructing the characteristics of the medium from -often noisy- observations. A nonlinear functional is minimized, which involves both the misfit to the measurements and a Tikhonov-type regularization term to tackle inherent ill-posedness. Achieving scalability for the inversion process on tens of thousands of multicore processors is a task that offers many research challenges. We initiated global "adjoint tomography" using 253 earthquakes and produced the first-generation model named GLAD-M15, with a transversely isotropic model parameterization. We are currently running iterations for a second-generation anisotropic model based on the same 253 events. In parallel, we continue iterations for a transversely isotropic model with a larger dataset of 1,040 events to determine higher-resolution plume and slab images. A significant part of our research has focused on eliminating I/O bottlenecks in the adjoint tomography workflow. This has led to the development of a new Adaptable Seismic Data Format based on HDF5, and post-processing tools based on the ADIOS library developed by Oak Ridge National Laboratory. We use the Ensemble Toolkit for workflow stabilization & management to automate the workflow with minimal human interaction.
Towards full waveform ambient noise inversion
Sager, Korbinian; Ermert, Laura; Boehm, Christian; Fichtner, Andreas
2018-01-01
In this work we investigate fundamentals of a method—referred to as full waveform ambient noise inversion—that improves the resolution of tomographic images by extracting waveform information from interstation correlation functions that cannot be used without knowing the distribution of noise sources. The fundamental idea is to drop the principle of Green function retrieval and to establish correlation functions as self-consistent observables in seismology. This involves the following steps: (1) We introduce an operator-based formulation of the forward problem of computing correlation functions. It is valid for arbitrary distributions of noise sources in both space and frequency, and for any type of medium, including 3-D elastic, heterogeneous and attenuating media. In addition, the formulation allows us to keep the derivations independent of time and frequency domain and it facilitates the application of adjoint techniques, which we use to derive efficient expressions to compute first and also second derivatives. The latter are essential for a resolution analysis that accounts for intra- and interparameter trade-offs. (2) In a forward modelling study we investigate the effect of noise sources and structure on different observables. Traveltimes are hardly affected by heterogeneous noise source distributions. On the other hand, the amplitude asymmetry of correlations is at least to first order insensitive to unmodelled Earth structure. Energy and waveform differences are sensitive to both structure and the distribution of noise sources. (3) We design and implement an appropriate inversion scheme, where the extraction of waveform information is successively increased. We demonstrate that full waveform ambient noise inversion has the potential to go beyond ambient noise tomography based on Green function retrieval and to refine noise source location, which is essential for a better understanding of noise generation. Inherent trade-offs between source and structure
Stochastic inverse problems: Models and metrics
Energy Technology Data Exchange (ETDEWEB)
Sabbagh, Elias H.; Sabbagh, Harold A.; Murphy, R. Kim [Victor Technologies, LLC, Bloomington, IN 47407-7706 (United States); Aldrin, John C. [Computational Tools, Gurnee, IL 60031 (United States); Annis, Charles [Statistical Engineering, Palm Beach Gardens, FL 33418 (United States); Knopp, Jeremy S. [Air Force Research Laboratory (AFRL/RXCA), Wright Patterson AFB, OH 45433-7817 (United States)
2015-03-31
In past work, we introduced model-based inverse methods, and applied them to problems in which the anomaly could be reasonably modeled by simple canonical shapes, such as rectangular solids. In these cases the parameters to be inverted would be length, width and height, as well as the occasional probe lift-off or rotation. We are now developing a formulation that allows more flexibility in modeling complex flaws. The idea consists of expanding the flaw in a sequence of basis functions, and then solving for the expansion coefficients of this sequence, which are modeled as independent random variables, uniformly distributed over their range of values. There are a number of applications of such modeling: 1. Connected cracks and multiple half-moons, which we have noted in a POD set. Ideally we would like to distinguish connected cracks from one long shallow crack. 2. Cracks of irregular profile and shape which have appeared in cold work holes during bolt-hole eddy-current inspection. One side of such cracks is much deeper than other. 3. L or C shaped crack profiles at the surface, examples of which have been seen in bolt-hole cracks. By formulating problems in a stochastic sense, we are able to leverage the stochastic global optimization algorithms in NLSE, which is resident in VIC-3D®, to answer questions of global minimization and to compute confidence bounds using the sensitivity coefficient that we get from NLSE. We will also address the issue of surrogate functions which are used during the inversion process, and how they contribute to the quality of the estimation of the bounds.
Unwrapped phase inversion for near surface seismic data
Choi, Yun Seok
2012-11-04
The Phase-wrapping is one of the main obstacles of waveform inversion. We use an inversion algorithm based on the instantaneous-traveltime that overcomes the phase-wrapping problem. With a high damping factor, the frequency-dependent instantaneous-traveltime inversion provides the stability of refraction tomography, with higher resolution results, and no arrival picking involved. We apply the instantaneous-traveltime inversion to the synthetic data generated by the elastic time-domain modeling. The synthetic data is a representative of the near surface seismic data. Although the inversion algorithm is based on the acoustic wave equation, the numerical examples show that the instantaneous-traveltime inversion generates a convergent velocity model, very similar to what we see from traveltime tomography.
Sadleir, John E.
2010-01-01
We have recently shown that normal-metal/superconductor (N/S) bilayer TESs (superconducting Transition-Edge Sensors) exhibit weak-link behavior. Our measurements were explained in terms of a longitudinal proximity effect model in which superconducting order from the higher transition temperature leads is induced into the TES bilayer plane over remarkably long distances (up to 290 micron). Here we extend our understanding to include TESs with added noise-mitigating normal-metal structures (N structures). We explain our results of an effect converse to the longitudinal proximity effect (LoPE), the lateral inverse proximity effect (LaiPE), for which the order parameter in the N/S bilayer is reduced due to the neighboring N structures. We present resistance and critical current measurements as a function of temperature and magnetic field taken on square Mo/Au bilayer TESs with lengths ranging from 8 to 130 micron with and without added N structures. We observe the inverse proximity effect on the bilayer over in-plane distances many tens of microns and find the transition shifts to lower temperature scale approximately as the inverse square of the in-plane N-structure separation distance, without appreciable broadening of the transition width. We find TESs with added Au structures exhibit weak-link behavior as evidenced by exponential temperature dependence of the critical current and Josephson-like oscillations of the critical current with applied magnetic field. We also present evidence for nonequilbrium superconductivity and estimate a quasiparticle lifetime of 1.8 x 10(exp -10) s for the bilayer. The LoPE model is also used to explain the increased conductivity at temperatures above the bilayer's steep resistive transition
Presentation: 3D magnetic inversion by planting anomalous densities
Uieda, Leonardo; Barbosa, Valeria C. F.
2013-01-01
Slides for the presentation "3D magnetic inversion by planting anomalous densities" given at the 2013 AGU Meeting of the Americas in Cancun, Mexico. Note: There was an error in the title of the talk. The correct title should be "3D magnetic inversion by planting anomalous magnetization" Abstract: We present a new 3D magnetic inversion algorithm based on the computationally efficient method of planting anomalous densities. The algorithm consists of an iterative growth of the an...
n-Colour even self-inverse compositions
Indian Academy of Sciences (India)
Agarwal [6] defined an n-colour self-inverse composition as follows: DEFINITION 1.2 [6]. An n-colour composition whose parts read from left to right are identical with when read from right to left and is called an n-colour self-inverse composition. Thus, for example there are 8 n-colour self-inverse compositions of 4, viz.,.
Large-Scale Inverse Problems and Quantification of Uncertainty
Biegler, Lorenz; Ghattas, Omar
2010-01-01
Large-scale inverse problems and associated uncertainty quantification has become an important area of research, central to a wide range of science and engineering applications. Written by leading experts in the field, Large-scale Inverse Problems and Quantification of Uncertainty focuses on the computational methods used to analyze and simulate inverse problems. The text provides PhD students, researchers, advanced undergraduate students, and engineering practitioners with the perspectives of researchers in areas of inverse problems and data assimilation, ranging from statistics and large-sca
Aftermath of Ankle Inversion Injuries: Spectrum of MR Imaging Findings.
Meehan, Timothy M; Martinez-Salazar, Edgar Leonardo; Torriani, Martin
2017-02-01
Acute and chronic ankle inversion injuries are a common source of pain and a diagnostic challenge. Several studies have shown a variety of injury patterns after inversion injury both in acute and chronic settings. Although traditional assessment with clinical examination and radiographs is generally accepted for inversion injuries, MR imaging is a useful tool to detect occult injuries and in patients with chronic symptoms. This article examines a range of MR imaging findings that may be present in patients with lateral ankle pain following an acute or chronic inversion injury. Copyright Â© 2016 Elsevier Inc. All rights reserved.
Level 1.5 Almucantar Inversion Products Phase Functions
National Aeronautics and Space Administration — AERONET inversion code provides aerosoloptical properties in the total atmospheric column derived from the direct and diffuse radiation measured byAERONETCimel...
Level 2.0 Almucantar Inversion Products Phase Functions
National Aeronautics and Space Administration — AERONET inversion code provides aerosoloptical properties in the total atmospheric column derived from the direct and diffuse radiation measured byAERONETCimel...
Chromatid Painting for Chromosomal Inversion Detection, Phase II
National Aeronautics and Space Administration — We propose the continued development of a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and...
Pericentric inversion of chromosome 12; a three family study
DEFF Research Database (Denmark)
Haagerup, A; Hertz, Jens Michael
1992-01-01
A pericentric inversion of chromosome 12 has been followed in three large independently ascertained Danish families. Out of a total number of 52 persons examined, 25 were found to carry the inversion. The breakpoints in all three families were localized to p13 and q13, resulting in more than one...... rate is calculated to be 0.58, which is not significantly different from an expected segregation rate of 0.5. In family 3, an additional inversion of a chromosome 9 has been found in 4 individuals. Our results are discussed in relation to previous findings and with respect to the genetic counselling...... of families with pericentric inversions....
Level 2.0 Almucantar Inversion Products (except phase functions)
National Aeronautics and Space Administration — AERONET inversion code provides aerosoloptical properties in the total atmospheric column derived from the direct and diffuse radiation measured byAERONETCimel...
Level 1.5 Almucantar Inversion Products (except phase functions)
National Aeronautics and Space Administration — AERONET inversion code provides aerosoloptical properties in the total atmospheric column derived from the direct and diffuse radiation measured byAERONETCimel...
Source-independent elastic waveform inversion using a logarithmic wavefield
Choi, Yun Seok
2012-01-01
The logarithmic waveform inversion has been widely developed and applied to some synthetic and real data. In most logarithmic waveform inversion algorithms, the subsurface velocities are updated along with the source estimation. To avoid estimating the source wavelet in the logarithmic waveform inversion, we developed a source-independent logarithmic waveform inversion algorithm. In this inversion algorithm, we first normalize the wavefields with the reference wavefield to remove the source wavelet, and then take the logarithm of the normalized wavefields. Based on the properties of the logarithm, we define three types of misfit functions using the following methods: combination of amplitude and phase, amplitude-only, and phase-only. In the inversion, the gradient is computed using the back-propagation formula without directly calculating the Jacobian matrix. We apply our algorithm to noise-free and noise-added synthetic data generated for the modified version of elastic Marmousi2 model, and compare the results with those of the source-estimation logarithmic waveform inversion. For the noise-free data, the source-independent algorithms yield velocity models close to true velocity models. For random-noise data, the source-estimation logarithmic waveform inversion yields better results than the source-independent method, whereas for coherent-noise data, the results are reversed. Numerical results show that the source-independent and source-estimation logarithmic waveform inversion methods have their own merits for random- and coherent-noise data. © 2011.
Group inverses of M-matrices and their applications
Kirkland, Stephen J
2013-01-01
Group inverses for singular M-matrices are useful tools not only in matrix analysis, but also in the analysis of stochastic processes, graph theory, electrical networks, and demographic models. Group Inverses of M-Matrices and Their Applications highlights the importance and utility of the group inverses of M-matrices in several application areas. After introducing sample problems associated with Leslie matrices and stochastic matrices, the authors develop the basic algebraic and spectral properties of the group inverse of a general matrix. They then derive formulas for derivatives of matrix f
... this page: //medlineplus.gov/ency/article/003400.htm Temperature measurement To use the sharing features on this page, please enable JavaScript. The measurement of body temperature can help detect illness. It can also monitor ...
3D stochastic inversion and joint inversion of potential fields for multi scale parameters
Shamsipour, Pejman
In this thesis we present the development of new techniques for the interpretation of potential field (gravity and magnetic data), which are the most widespread economic geophysical methods used for oil and mineral exploration. These new techniques help to address the long-standing issue with the interpretation of potential fields, namely the intrinsic non-uniqueness inversion of these types of data. The thesis takes the form of three papers (four including Appendix), which have been published, or soon to be published, in respected international journals. The purpose of the thesis is to introduce new methods based on 3D stochastical approaches for: 1) Inversion of potential field data (magnetic), 2) Multiscale Inversion using surface and borehole data and 3) Joint inversion of geophysical potential field data. We first present a stochastic inversion method based on a geostatistical approach to recover 3D susceptibility models from magnetic data. The aim of applying geostatistics is to provide quantitative descriptions of natural variables distributed in space or in time and space. We evaluate the uncertainty on the parameter model by using geostatistical unconditional simulations. The realizations are post-conditioned by cokriging to observation data. In order to avoid the natural tendency of the estimated structure to lay near the surface, depth weighting is included in the cokriging system. Then, we introduce algorithm for multiscale inversion, the presented algorithm has the capability of inverting data on multiple supports. The method involves four main steps: i. upscaling of borehole parameters (It could be density or susceptibility) to block parameters, ii. selection of block to use as constraints based on a threshold on kriging variance, iii. inversion of observation data with selected block densities as constraints, and iv. downscaling of inverted parameters to small prisms. Two modes of application are presented: estimation and simulation. Finally, a novel
Nonlinear problems in fluid dynamics and inverse scattering: Nonlinear waves and inverse scattering
Ablowitz, Mark J.
1994-12-01
Research investigations involving the fundamental understanding and applications of nonlinear wave motion and related studies of inverse scattering and numerical computation have been carried out and a number of significant results have been obtained. A class of nonlinear wave equations which can be solved by the inverse scattering transform (IST) have been studied, including the Kadaomtsev-Petviashvili (KP) equation, the Davey-Stewartson equation, and the 2+1 Toda system. The solutions obtained by IST correspond to the Cauchy initial value problem with decaying initial data. We have also solved two important systems via the IST method: a 'Volterra' system in 2+1 dimensions and a new one dimensional nonlinear equation which we refer to as the Toda differential-delay equation. Research in computational chaos in moderate to long time numerical simulations continues.
2011-06-01
shape of a scatterer from re ected acoustic waves, using a Banach space setting and the Lagrangian approach. The shape Hessian is then analyzed in both H...corresponding to the inverse problem of inferring the shape of a scatterer from reflected acoustic waves, using a Banach space setting and the...compact embeddings in Hölder and Sobolev spaces . These tools allow us to state the shape derivatives in a Banach space setting, and then to analyze the
More Bayesian Transdimensional Inversion for Thermal History Modelling (Invited)
Gallagher, K.
2013-12-01
Since the publication of Dodson (1973) quantifying the relationship between geochronogical ages and closure temperatures, an ongoing concern in thermochronology is reconstruction of thermal histories consistent with the measured data. Extracting this thermal history information is best treated as an inverse problem, given the complex relationship between the observations and the thermal history. When solving the inverse problem (i.e. finding thermal acceptable thermal histories), stochastic sampling methods have often been used, as these are relatively global when searching the model space. However, the issue remains how best to estimate those parts of the thermal history unconstrained by independent information, i.e. what is required to fit the data ? To solve this general problem, we use a Bayesian transdimensional Markov Chain Monte Carlo method and this has been integrated into user-friendly software, QTQt (Quantitative Thermochronology with Qt), which runs on both Macintosh and PC. The Bayesian approach allows us to consider a wide range of possible thermal history as general prior information on time, temperature (and temperature offset for multiple samples in a vertical profile). We can also incorporate more focussed geological constraints in terms of more specific priors. In this framework, it is the data themselves (and their errors) that determine the complexity of the thermal history solutions. For example, more precise data will justify a more complex solution, while more noisy data will be happy with simpler solutions. We can express complexity in terms of the number of time-temperature points defining the total thermal history. Another useful feature of this method is that was can easily deal with imprecise parameter values (e.g. kinetics, data errors), by drawing samples from a user specified probability distribution, rather than using a single value. Finally, the method can be applied to either single samples, or multiple samples (from a borehole or
New analysis indicates no thermal inversion in the atmosphere of HD 209458b
International Nuclear Information System (INIS)
Diamond-Lowe, Hannah; Stevenson, Kevin B.; Bean, Jacob L.; Line, Michael R.; Fortney, Jonathan J.
2014-01-01
An important focus of exoplanet research is the determination of the atmospheric temperature structure of strongly irradiated gas giant planets, or hot Jupiters. HD 209458b is the prototypical exoplanet for atmospheric thermal inversions, but this assertion does not take into account recently obtained data or newer data reduction techniques. We reexamine this claim by investigating all publicly available Spitzer Space Telescope secondary-eclipse photometric data of HD 209458b and performing a self-consistent analysis. We employ data reduction techniques that minimize stellar centroid variations, apply sophisticated models to known Spitzer systematics, and account for time-correlated noise in the data. We derive new secondary-eclipse depths of 0.119% ± 0.007%, 0.123% ± 0.006%, 0.134% ± 0.035%, and 0.215% ± 0.008% in the 3.6, 4.5, 5.8, and 8.0 μm bandpasses, respectively. We feed these results into a Bayesian atmospheric retrieval analysis and determine that it is unnecessary to invoke a thermal inversion to explain our secondary-eclipse depths. The data are well fitted by a temperature model that decreases monotonically between pressure levels of 1 and 0.01 bars. We conclude that there is no evidence for a thermal inversion in the atmosphere of HD 209458b.
Short-range inverse-square law experiment in space
International Nuclear Information System (INIS)
Strayer, D.M.; Paik, H.J.; Moody, M.V.
2003-01-01
The objective of ISLES (inverse-square law experiment in space) is to perform a null test of Newton's law on the ISS with a resolution of one part in 10 5 at ranges from 100 mm to 1 mm. ISLES will be sensitive enough to detect axions with the strongest allowed coupling and to test the string-theory prediction with R>= 5 μm. To accomplish these goals on the rather noisy International Space Station, the experiment is set up to provide immunity from the vibrations and other common-mode accelerations. The measures to be applied for reducing the effects of disturbances will be described in this presentation. As designed, the experiment will be cooled to less than 2 K in NASA's low temperature facility the LTMPF, allowing superconducting magnetic levitation in microgravity to obtain very soft, low-loss suspension of the test masses. The low-damping magnetic levitation, combined with a low-noise SQUID, leads to extremely low intrinsic noise in the detector. To minimize Newtonian errors, ISLES employs a near-null source of gravity, a circular disk of large diameter-to-thickness ratio. Two test masses, also disk-shaped, are suspended on the two sides of the source mass at a distance of 100 μm to 1 mm. The signal is detected by a superconducting differential accelerometer, making a highly sensitive sensor of the gravity force generated by the source mass
Inverse Leidenfrost Effect: Levitating Drops on Liquid Nitrogen.
Adda-Bedia, M; Kumar, S; Lechenault, F; Moulinet, S; Schillaci, M; Vella, D
2016-05-03
We explore the interaction between a liquid drop (initially at room temperature) and a bath of liquid nitrogen. In this scenario, heat transfer occurs through film-boiling: a nitrogen vapor layer develops that may cause the drop to levitate at the bath surface. We report the phenomenology of this inverse Leidenfrost effect, investigating the effect of the drop size and density by using an aqueous solution of a tungsten salt to vary the drop density. We find that (depending on its size and density) a drop either levitates or instantaneously sinks into the bulk nitrogen. We begin by measuring the duration of the levitation as a function of the radius R and density ρd of the liquid drop. We find that the levitation time increases roughly linearly with drop radius but depends weakly on the drop density. However, for sufficiently large drops, R ≥ Rc(ρd), the drop sinks instantaneously; levitation does not occur. This sinking of a (relatively) hot droplet induces film-boiling, releasing a stream of vapor bubbles for a well-defined length of time. We study the duration of this immersed-drop bubbling finding similar scalings (but with different prefactors) to the levitating drop case. With these observations, we study the physical factors limiting the levitation and immersed-film-boiling times, proposing a simple model that explains the scalings observed for the duration of these phenomena, as well as the boundary of (R,ρd) parameter space that separates them.
Inverse Leidenfrost effect: self-propelling drops on a bath
Gauthier, Anais; van der Meer, Devaraj; Lohse, Detlef; Physics of Fluids Team
2017-11-01
When deposited on very hot solid, volatile drops can levitate over a cushion of vapor, in the so-called Leidenfrost state. This phenomenon can also be observed on a hot bath and similarly to the solid case, drops are very mobile due to the absence of contact with the substrate that sustains them. We discuss here a situation of ``inverse Leidenfrost effect'' where room-temperature drops levitate on a liquid nitrogen pool - the vapor is generated here by the bath sustaining the relatively hot drop. We show that the drop's movement is not random: the liquid goes across the bath in straight lines, a pattern only disrupted by elastic bouncing on the edges. In addition, the drops are initially self-propelled; first at rest, they accelerate for a few seconds and reach velocities of the order of a few cm/s, before slowing down. We investigate experimentally the parameters that affect their successive acceleration and deceleration, such as the size and nature of the drops and we discuss the origin of this pattern.
Computer-Assisted Inverse Design of Inorganic Electrides
Directory of Open Access Journals (Sweden)
Yunwei Zhang
2017-02-01
Full Text Available Electrides are intrinsic electron-rich materials enabling applications as excellent electron emitters, superior catalysts, and strong reducing agents. There are a number of organic electrides; however, their instability at room temperature and sensitivity to moisture are bottlenecks for their practical uses. Known inorganic electrides are rare, but they appear to have greater thermal stability at ambient conditions and are thus better characterized for application. Here, we develop a computer-assisted inverse-design method for searching for a large variety of inorganic electrides unbiased by any known electride structures. It uses the intrinsic property of interstitial electron localization of electrides as the global variable function for swarm intelligence structure searches. We construct two rules of thumb on the design of inorganic electrides pointing to electron-rich ionic systems and low electronegativity of the cationic elements involved. By screening 99 such binary compounds through large-scale computer simulations, we identify 24 stable and 65 metastable new inorganic electrides that show distinct three-, two-, and zero-dimensional conductive properties, among which 18 are existing compounds that have not been pointed to as electrides. Our work reveals the rich abundance of inorganic electrides by providing 33 hitherto unexpected structure prototypes of electrides, of which 19 are not in the known structure databases.
Optical properties of inversion domain boundaries in GaN
Energy Technology Data Exchange (ETDEWEB)
Kure, Thomas; Kirste, Ronny; Callsen, Gordon; Reparaz, Juan Sebastian; Hoffmann, Axel [Technische Universitaet Berlin, Berlin (Germany); Collazo, Ramon; Sitar, Zlatko [North Carolina State University, Raleigh, North Carolina (United States); HexaTech Inc., Raleigh, North Carolina (United States); Rice, Anthony [North Carolina State University, Raleigh, North Carolina (United States); Mita, Seji; Xie, Jinqiao [HexaTech Inc., Raleigh, North Carolina (United States)
2011-07-01
Influenced by the growth method and growth parameters the polarity of epitaxial grown GaN films can be manipulated to form pure N- or Ga-polarity or states of mixed polarity. GaN grown on heterosubstrates can even form spatially adjacent areas of different polarities differentiated by an inversion domain boundary (IDB). Besides their structural differences each of the areas has unique optical properties, likewise the IDB itself. Furthermore, due to a polar selective doping behaviour, it is possible to fabricate a lateral p/n junction. Using spatially-resolved photoluminescence spectroscopy ({mu}-PL) we revealed a temperature dependant enhancement of the luminescence by one order of magnitude at the IDB. Thereby, we confirmed an earlier published model. Samples intentionally doped with Mg, which led to a p/n-junction, revealed an unexpected difference of the enhancement compared to the undoped samples. In addition, we used spatially-resolved electroluminescence spectroscopy ({mu}-EL) to investigate the influence of an external electric field.
Structure-property maps and optimal inversion in configurational thermodynamics
Arnold, Björn; Díaz Ortiz, Alejandro; Hart, Gus L. W.; Dosch, Helmut
2010-03-01
Cluster expansions of first-principles density-functional databases in multicomponent systems are now used as a routine tool for the prediction of zero- and finite-temperature physical properties. The ability of producing large databases of various degrees of accuracy, i.e., high-throughput calculations, makes pertinent the analysis of error propagation during the inversion process. This is a very demanding task as both data and numerical noise have to be treated on equal footing. We have addressed this problem by using an analysis that combines the variational and evolutionary approaches to cluster expansions. Simulated databases were constructed ex professo to sample the configurational space in two different and complementary ways. These databases were in turn treated with different levels of both systematic and random numerical noise. The effects of the cross-validation level, size of the database, type of numerical imprecisions on the forecasting power of the expansions were extensively analyzed. We found that the size of the database is the most important parameter. Upon this analysis, we have determined criteria for selecting the optimal expansions, i.e., transferable expansions with constant forecasting power in the configurational space (a structure-property map). As a by-product, our study provides a detailed comparison between the variational cluster expansion and the genetic-algorithm approaches.
Simultaneous Inversion of Full Data Bandwidth by Tomographic Full Waveform Inversion
Almomin, A. A.; Biondi, B. C.
2015-12-01
The convergence of full-waveform inversion can be improved by extending the velocity model along either the subsurface-offset axis or the time-lag axis. The extension of the velocity model along the time-lag axis enables us to linearly model large time shifts caused by velocity perturbations. This linear modeling was based on a new linearization of the scalar wave equation in which perturbation of the extended slowness squared was convolved in time with the second time derivative of the background wavefield. The linearization was accurate for reflected events and transmitted events. We determined that it can effectively model conventional reflection data as well as modern long-offset data containing diving waves. It also enabled the simultaneous inversion of reflections and diving waves, even when the starting velocity model was far from being accurate. We solved the optimization problem related to the inversion with a nested algorithm. The inner iterations were based on the proposed linearization and on a mixing of scales between the short- and long-wavelength components of the velocity model. We significantly improved the convergence rate by preconditioning the extended model to balance the amplitude-versus-angle behavior of the wave-equation and by imposing wavelength continuation of the gradient in the outer loop. Numerical tests performed on synthetic data modeled on the Marmousi model and on Chevron's FWI blind-test data demonstrated the global convergence properties as well as the high-resolution potential of the proposed method.
Two-dimensional inversion of MT (magnetotelluric) data; MT ho no nijigen inversion kaiseki
Energy Technology Data Exchange (ETDEWEB)
Ito, S.; Okuno, M.; Ushijima, K.; Mizunaga, H. [Kyushu University, Fukuoka (Japan). Faculty of Engineering
1997-05-27
A program has been developed to conduct inversion analysis of two-dimensional model using MT data, accurately. For the developed program, finite element method (FEM) was applied to the section of sequential analysis. A method in which Jacobian matrix is calculated only one first time and is inversely analyzed by fixing this during the repetition, and a method in which Jacobian matrix is corrected at each repetition of inversion analysis, were compared mutually. As a result of the numerical simulation, it was revealed that the Jacobian correction method provided more stable convergence for the simple 2D model, and that the calculation time is almost same as that of the Jacobian fixation method. To confirm the applicability of this program to actually measured data, results obtained from this program were compared with those from the Schlumberger method analysis by using MT data obtained in the Hatchobara geothermal area. Consequently, it was demonstrated that the both are well coincided mutually. 17 refs., 7 figs.
Testing the gravitational inverse-square law
International Nuclear Information System (INIS)
Adelberger, Eric; Heckel, B.; Hoyle, C.D.
2005-01-01
If the universe contains more than three spatial dimensions, as many physicists believe, our current laws of gravity should break down at small distances. When Isaac Newton realized that the acceleration of the Moon as it orbited around the Earth could be related to the acceleration of an apple as it fell to the ground, it was the first time that two seemingly unrelated physical phenomena had been 'unified'. The quest to unify all the forces of nature is one that still keeps physicists busy today. Newton showed that the gravitational attraction between two point bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. Newton's theory, which assumes that the gravitational force acts instantaneously, remained essentially unchallenged for roughly two centuries until Einstein proposed the general theory of relativity in 1915. Einstein's radical new theory made gravity consistent with the two basic ideas of relativity: the world is 4D - the three directions of space combined with time - and no physical effect can travel faster than light. The theory of general relativity states that gravity is not a force in the usual sense but a consequence of the curvature of this space-time produced by mass or energy. However, in the limit of low velocities and weak gravitational fields, Einstein's theory still predicts that the gravitational force between two point objects obeys an inverse-square law. One of the outstanding challenges in physics is to finish what Newton started and achieve the ultimate 'grand unification' - to unify gravity with the other three fundamental forces (the electromagnetic force, and the strong and weak nuclear forces) into a single quantum theory. In string theory - one of the leading candidates for an ultimate theory - the fundamental entities of nature are 1D strings and higher-dimensional objects called 'branes', rather than the point-like particles we are familiar with. String
Inverse analysis of turbidites by machine learning
Naruse, H.; Nakao, K.
2017-12-01
This study aims to propose a method to estimate paleo-hydraulic conditions of turbidity currents from ancient turbidites by using machine-learning technique. In this method, numerical simulation was repeated under various initial conditions, which produces a data set of characteristic features of turbidites. Then, this data set of turbidites is used for supervised training of a deep-learning neural network (NN). Quantities of characteristic features of turbidites in the training data set are given to input nodes of NN, and output nodes are expected to provide the estimates of initial condition of the turbidity current. The optimization of weight coefficients of NN is then conducted to reduce root-mean-square of the difference between the true conditions and the output values of NN. The empirical relationship with numerical results and the initial conditions is explored in this method, and the discovered relationship is used for inversion of turbidity currents. This machine learning can potentially produce NN that estimates paleo-hydraulic conditions from data of ancient turbidites. We produced a preliminary implementation of this methodology. A forward model based on 1D shallow-water equations with a correction of density-stratification effect was employed. This model calculates a behavior of a surge-like turbidity current transporting mixed-size sediment, and outputs spatial distribution of volume per unit area of each grain-size class on the uniform slope. Grain-size distribution was discretized 3 classes. Numerical simulation was repeated 1000 times, and thus 1000 beds of turbidites were used as the training data for NN that has 21000 input nodes and 5 output nodes with two hidden-layers. After the machine learning finished, independent simulations were conducted 200 times in order to evaluate the performance of NN. As a result of this test, the initial conditions of validation data were successfully reconstructed by NN. The estimated values show very small
Weisz-Patrault , Daniel
2012-01-01
This thesis is about the use of analytical mathematics within the framework of inverse methods applied to industry. These works are devoted to the development of sensors using real-time inverse methods adapted for rolling process. Steel producer ArcelorMittal leads a European project that aims to demonstrate the feasibility of sensors measuring fields (temperature, stress) in the contact between the product and the tool without altering physical conditions of this contact. The thesis has been...
Directory of Open Access Journals (Sweden)
A. Solomon
2011-10-01
Full Text Available Observations suggest that processes maintaining subtropical and Arctic stratocumulus differ, due to the different environments in which they occur. For example, specific humidity inversions (specific humidity increasing with height are frequently observed to occur near cloud top coincident with temperature inversions in the Arctic, while they do not occur in the subtropics. In this study we use nested LES simulations of decoupled Arctic Mixed-Phase Stratocumulus (AMPS clouds observed during the DOE Atmospheric Radiation Measurement Program's Indirect and SemiDirect Aerosol Campaign (ISDAC to analyze budgets of water components, potential temperature, and turbulent kinetic energy. These analyses quantify the processes that maintain decoupled AMPS, including the role of humidity inversions. Key structural features include a shallow upper entrainment zone at cloud top that is located within the temperature and humidity inversions, a mixed layer driven by cloud-top cooling that extends from the base of the upper entrainment zone to below cloud base, and a lower entrainment zone at the base of the mixed layer. The surface layer below the lower entrainment zone is decoupled from the cloud mixed-layer system. Budget results show that cloud liquid water is maintained in the upper entrainment zone near cloud top (within a temperature and humidity inversion due to a down gradient transport of water vapor by turbulent fluxes into the cloud layer from above and direct condensation forced by radiative cooling. Liquid water is generated in the updraft portions of the mixed-layer eddies below cloud top by buoyant destabilization. These processes cause at least 20% of the cloud liquid water to extend into the inversion. The redistribution of water vapor from the top of the humidity inversion to its base maintains the cloud layer, while the mixed layer-entrainment zone system is continually losing total water. In this decoupled system, the humidity inversion is
Energy Technology Data Exchange (ETDEWEB)
Singh, Anshika; Kumari, Reetu; Kumar, Vinay; Krishnia, Lucky; Naqvi, Zainab; Panwar, Amrish K. [Department of Applied Physics, Delhi Technological University, Delhi, 110042 (India); Bhatta, Umananda M. [Centre for Emerging Technologies, Jain University, Jakkasandra, Kanakapura Taluk, Ramanagaram Dist, Karnataka, PIN 562 112 (India); Ghosh, Arnab; Satyam, P.V. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Tyagi, Pawan K., E-mail: pawantyagi@dce.edu [Department of Applied Physics, Delhi Technological University, Delhi, 110042 (India)
2016-01-01
Graphical abstract: - Highlights: • In-situ response of iron carbide (Fe{sub 3}C) nanorod filled inside carbon nanotube (CNT) under electron irradiation has been studied at room and high temperature. • Inverse Ostwald ripening and morphological changes in both carbon nanotube as well as nanorod are observed. • Compression generated either by electron beam heating or by shrinkage of CNT walls has been observed to be a decisive factor. • Temperature during the irradiation shows high impact on irradiation induced changes. - Abstract: The present study aims to deduce the in-situ response of iron carbide (Fe{sub 3}C) nanorod filled inside carbon nanotube (CNT) under electron irradiation. Electron irradiation on Fe{sub 3}C filled-CNT at both high and room temperature (RT) has been performed inside transmission electron microscope. At high temperature (HT), it has been found that γ-Fe atoms in lattice of Fe{sub 3}C nanorod accumulate first and then form the cluster. These clusters follow the inverse Ostwald ripening whereas if e-irradiation is performed at RT then only the morphological changes in both carbon nanotube as well as nanorod are observed. Compression generated either by electron beam heating or by shrinkage of CNT walls is observed to be a decisive factor.
Inverse magnetic catalysis from improved holographic QCD in the Veneziano limit
International Nuclear Information System (INIS)
Gürsoy, Umut; Iatrakis, Ioannis; Järvinen, Matti; Nijs, Govert
2017-01-01
We study the dependence of the chiral condensate on external magnetic field in the context of holographic QCD at large number of flavors. We consider a holographic QCD model where the flavor degrees of freedom fully backreact on the color dynamics. Perturbative QCD calculations have shown that B acts constructively on the chiral condensate, a phenomenon called “magnetic catalysis”. In contrast, recent lattice calculations show that, depending on the number of flavors and temperature, the magnetic field may also act destructively, which is called “inverse magnetic catalysis”. Here we show that the holographic theory is capable of both behaviors depending on the choice of parameters. For reasonable choice of the potentials entering the model we find qualitative agreement with the lattice expectations. Our results provide insight for the physical reasons behind the inverse magnetic catalysis. In particular, we argue that the backreaction of the flavors to the background geometry decatalyzes the condensate.
Charge Inversion in semi-permeable membranes
Das, Siddhartha; Sinha, Shayandev; Jing, Haoyuan
Role of semi-permeable membranes like lipid bilayer is ubiquitous in a myriad of physiological and pathological phenomena. Typically, lipid membranes are impermeable to ions and solutes; however, protein channels embedded in the membrane allow the passage of selective, small ions across the membrane enabling the membrane to adopt a semi-permeable nature. This semi-permeability, in turn, leads to electrostatic potential jump across the membrane, leading to effects such as regulation of intracellular calcium, extracellular-vesicle-membrane interactions, etc. In this study, we theoretically demonstrate that this semi-permeable nature may trigger the most remarkable charge inversion (CI) phenomenon in the cytosol-side of the negatively-charged lipid bilayer membrane that are selectively permeable to only positive ions of a given salt. This CI is manifested as the changing of the sign of the electrostatic potential from negative to positive from the membrane-cytosol interface to deep within the cytosol. We study the impact of the parameters such as the concentration of this salt with selectively permeable ions as well as the concentration of an external salt in the development of this CI phenomenon. We anticipate such CI will profoundly influence the interaction of membrane and intra-cellular moieties (e.g., exosome or multi-cellular vesicles) having implications for a host of biophysical processes.
Image-domain full waveform inversion
Zhang, Sanzong
2013-08-20
The main difficulty with the data-domain full waveform inversion (FWI) is that it tends to get stuck in the local minima associated with the waveform misfit function. This is because the waveform misfit function is highly nonlinear with respect to changes in velocity model. To reduce this nonlinearity, we define the image-domain objective function to minimize the difference of the suboffset-domain common image gathers (CIGs) obtained by migrating the observed data and the calculated data. The derivation shows that the gradient of this new objective function is the combination of the gradient of the conventional FWI and the image-domain differential semblance optimization (DSO). Compared to the conventional FWI, the imagedomain FWI is immune to cycle skipping problems by smearing the nonzero suboffset images along wavepath. It also can avoid the edge effects and the gradient artifacts that are inherent in DSO due to the falsely over-penalized focused images. This is achieved by subtracting the focused image associated with the calculated data from the unfocused image associated with the observed data in the image-domain misfit function. The numerical results of the Marmousi model show that image-domain FWI is less sensitive the initial model than the conventional FWI. © 2013 SEG.
Soft leptogenesis in the inverse seesaw model
Garayoa, Julia; Concepion Gonzalez-Garcia, Maria; Rius, Nuria
2007-02-01
We consider leptogenesis induced by soft supersymmetry breaking terms (``soft leptogenesis''), in the context of the inverse seesaw mechanism. In this model there are lepton number (L) conserving and L-violating soft supersymmetry-breaking B-terms involving the singlet sneutrinos which, together with the — generically small — L-violating parameter responsible of the neutrino mass, give a small mass splitting between the four singlet sneutrino states of a single generation. In combination with the trilinear soft supersymmetry breaking terms they also provide new CP violating phases needed to generate a lepton asymmetry in the singlet sneutrino decays. We obtain that in this scenario the lepton asymmetry is proportional to the L-conserving soft supersymmetry-breaking B-term, and it is not suppressed by the L-violating parameters. Consequently we find that, as in the standard see-saw case, this mechanism can lead to sucessful leptogenesis only for relatively small value of the relevant soft bilinear coupling. The right-handed neutrino masses can be sufficiently low to elude the gravitino problem. Also the corresponding Yukawa couplings involving the lightest of the right-handed neutrinos are constrained to be ∑|Y1k|2lesssim10-7 which generically implies that the neutrino mass spectrum has to be strongly hierarchical.
Towards inverse modeling of intratumor heterogeneity
Brutovsky, Branislav; Horvath, Denis
2015-08-01
Development of resistance limits efficiency of present anticancer therapies and preventing it remains a big challenge in cancer research. It is accepted, at the intuitive level, that resistance emerges as a consequence of the heterogeneity of cancer cells at the molecular, genetic and cellular levels. Produced by many sources, tumor heterogeneity is extremely complex time dependent statistical characteristics which may be quantified by measures defined in many different ways, most of them coming from statistical mechanics. In this paper, we apply the Markovian framework to relate population heterogeneity to the statistics of the environment. As, from an evolutionary viewpoint, therapy corresponds to a purposeful modi- fication of the cells' fitness landscape, we assume that understanding general relationship between the spatiotemporal statistics of a tumor microenvironment and intratumor heterogeneity will allow to conceive the therapy as an inverse problem and to solve it by optimization techniques. To account for the inherent stochasticity of biological processes at cellular scale, the generalized distancebased concept was applied to express distances between probabilistically described cell states and environmental conditions, respectively.
Phaseless tomographic inverse scattering in Banach spaces
Estatico, C.; Fedeli, A.; Pastorino, M.; Randazzo, A.; Tavanti, E.
2016-10-01
In conventional microwave imaging, a hidden dielectric object under test is illuminated by microwave incident waves and the field it scatters is measured in magnitude and phase in order to retrieve the dielectric properties by solving the related non-homogenous Helmholtz equation or its Lippmann-Schwinger integral formulation. Since the measurement of the phase of electromagnetic waves can be still considered expensive in real applications, in this paper only the magnitude of the scattering wave fields is measured in order to allow a reduction of the cost of the measurement apparatus. In this respect, we firstly analyse the properties of the phaseless scattering nonlinear forward modelling operator in its integral form and we provide an analytical expression for computing its Fréchet derivative. Then, we propose an inexact Newton method to solve the associated nonlinear inverse problems, where any linearized step is solved by a Lp Banach space iterative regularization method which acts on the dual space Lp* . Indeed, it is well known that regularization in special Banach spaces, such us Lp with 1 < p < 2, allows to promote sparsity and to reduce Gibbs phenomena and over-smoothness. Preliminary results concerning numerically computed field data are shown.
Direct and Inverse Problems in Statistical Wavefields
International Nuclear Information System (INIS)
Wolf, Emil
2002-01-01
In this report account is presented of research carried out during the period September 1, 1999-August 31, 2002 under the sponsorship of the Department of Energy, grant DE-FG02-90ER14119. The research covered several areas of modern optical physics, particularly propagation of partially coherent light and its interaction with deterministic and with random media, spectroscopy with partially coherent light, polarization properties of statistical wave fields, effects of moving diffusers on coherence and on the spectra of light transmitted and scattered by them, reciprocity inequalities involving spatial and angular correlations of partially coherent beams, spreading of partially coherent beams in-random media, inverse source problems, computed and diffraction tomography and partially coherent solitons. We have discovered a new phenomenon in an emerging field of physical optics, known as singular optics; specifically we found that the spectrum of light changes drastically in the neighborhood of points where the intensity has zero value and where, consequently, the phase becomes singular, We noted some potential applications of this phenomenon. The results of our investigations were reported in 39 publications. They are listed on pages 3 to 5. Summaries of these publications are given on pages 6-13. Scientists who have participated in this research are listed on page 14
Inverse Magnus effect on a rotating sphere
Kim, Jooha; Park, Hyungmin; Choi, Haecheon; Yoo, Jung Yul
2011-11-01
In this study, we investigate the flow characteristics of rotating spheres in the subcritical Reynolds number (Re) regime by measuring the drag and lift forces on the sphere and the two-dimensional velocity in the wake. The experiment is conducted in a wind tunnel at Re = 0 . 6 ×105 - 2 . 6 ×105 and the spin ratio (ratio of surface velocity to the free-stream velocity) of 0 (no spin) - 0.5. The drag coefficient on a stationary sphere remains nearly constant at around 0.52. However, the magnitude of lift coefficient is nearly zero at Re Magnus effect, depending on the magnitudes of the Reynolds number and spin ratio. The velocity field measured from a particle image velocimetry (PIV) indicates that non-zero lift coefficient on a stationary sphere at Re > 2 . 0 ×105 results from the asymmetry of separation line, whereas the inverse Magnus effect for the rotating sphere results from the differences in the boundary-layer growth and separation along the upper and lower sphere surfaces. Supported by the WCU, Converging Research Center and Priority Research Centers Program, NRF, MEST, Korea.
Source Estimation by Full Wave Form Inversion
Energy Technology Data Exchange (ETDEWEB)
Sjögreen, Björn [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing; Petersson, N. Anders [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Applied Scientific Computing
2013-08-07
Given time-dependent ground motion recordings at a number of receiver stations, we solve the inverse problem for estimating the parameters of the seismic source. The source is modeled as a point moment tensor source, characterized by its location, moment tensor components, the start time, and frequency parameter (rise time) of its source time function. In total, there are 11 unknown parameters. We use a non-linear conjugate gradient algorithm to minimize the full waveform misfit between observed and computed ground motions at the receiver stations. An important underlying assumption of the minimization problem is that the wave propagation is accurately described by the elastic wave equation in a heterogeneous isotropic material. We use a fourth order accurate finite difference method, developed in [12], to evolve the waves forwards in time. The adjoint wave equation corresponding to the discretized elastic wave equation is used to compute the gradient of the misfit, which is needed by the non-linear conjugated minimization algorithm. A new source point moment source discretization is derived that guarantees that the Hessian of the misfit is a continuous function of the source location. An efficient approach for calculating the Hessian is also presented. We show how the Hessian can be used to scale the problem to improve the convergence of the non-linear conjugated gradient algorithm. Numerical experiments are presented for estimating the source parameters from synthetic data in a layer over half-space problem (LOH.1), illustrating rapid convergence of the proposed approach.
Inverse Stochastic Resonance in Cerebellar Purkinje Cells.
Directory of Open Access Journals (Sweden)
Anatoly Buchin
2016-08-01
Full Text Available Purkinje neurons play an important role in cerebellar computation since their axons are the only projection from the cerebellar cortex to deeper cerebellar structures. They have complex internal dynamics, which allow them to fire spontaneously, display bistability, and also to be involved in network phenomena such as high frequency oscillations and travelling waves. Purkinje cells exhibit type II excitability, which can be revealed by a discontinuity in their f-I curves. We show that this excitability mechanism allows Purkinje cells to be efficiently inhibited by noise of a particular variance, a phenomenon known as inverse stochastic resonance (ISR. While ISR has been described in theoretical models of single neurons, here we provide the first experimental evidence for this effect. We find that an adaptive exponential integrate-and-fire model fitted to the basic Purkinje cell characteristics using a modified dynamic IV method displays ISR and bistability between the resting state and a repetitive activity limit cycle. ISR allows the Purkinje cell to operate in different functional regimes: the all-or-none toggle or the linear filter mode, depending on the variance of the synaptic input. We propose that synaptic noise allows Purkinje cells to quickly switch between these functional regimes. Using mutual information analysis, we demonstrate that ISR can lead to a locally optimal information transfer between the input and output spike train of the Purkinje cell. These results provide the first experimental evidence for ISR and suggest a functional role for ISR in cerebellar information processing.
On some Toeplitz matrices and their inversions
Directory of Open Access Journals (Sweden)
S. Dutta
2014-10-01
Full Text Available In this article, using the difference operator B(a[m], we introduce a lower triangular Toeplitz matrix T which includes several difference matrices such as Δ(1,Δ(m,B(r,s,B(r,s,t, and B(r̃,s̃,t̃,ũ in different special cases. For any x ∈ w and m∈N0={0,1,2,…}, the difference operator B(a[m] is defined by (B(a[m]xk=ak(0xk+ak-1(1xk-1+ak-2(2xk-2+⋯+ak-m(mxk-m,(k∈N0 where a[m] = {a(0, a(1, …, a(m} and a(i = (ak(i for 0 ⩽ i ⩽ m are convergent sequences of real numbers. We use the convention that any term with negative subscript is equal to zero. The main results of this article relate to the determination and applications of the inverse of the Toeplitz matrix T.
Full Waveform Inversion Using Nonlinearly Smoothed Wavefields
Li, Y.
2017-05-26
The lack of low frequency information in the acquired data makes full waveform inversion (FWI) conditionally converge to the accurate solution. An initial velocity model that results in data with events within a half cycle of their location in the observed data was required to converge. The multiplication of wavefields with slightly different frequencies generates artificial low frequency components. This can be effectively utilized by multiplying the wavefield with itself, which is nonlinear operation, followed by a smoothing operator to extract the artificially produced low frequency information. We construct the objective function using the nonlinearly smoothed wavefields with a global-correlation norm to properly handle the energy imbalance in the nonlinearly smoothed wavefield. Similar to the multi-scale strategy, we progressively reduce the smoothing width applied to the multiplied wavefield to welcome higher resolution. We calculate the gradient of the objective function using the adjoint-state technique, which is similar to the conventional FWI except for the adjoint source. Examples on the Marmousi 2 model demonstrate the feasibility of the proposed FWI method to mitigate the cycle-skipping problem in the case of a lack of low frequency information.
Phaseless tomographic inverse scattering in Banach spaces
International Nuclear Information System (INIS)
Estatico, C.; Fedeli, A.; Pastorino, M.; Randazzo, A.; Tavanti, E.
2016-01-01
In conventional microwave imaging, a hidden dielectric object under test is illuminated by microwave incident waves and the field it scatters is measured in magnitude and phase in order to retrieve the dielectric properties by solving the related non-homogenous Helmholtz equation or its Lippmann-Schwinger integral formulation. Since the measurement of the phase of electromagnetic waves can be still considered expensive in real applications, in this paper only the magnitude of the scattering wave fields is measured in order to allow a reduction of the cost of the measurement apparatus. In this respect, we firstly analyse the properties of the phaseless scattering nonlinear forward modelling operator in its integral form and we provide an analytical expression for computing its Fréchet derivative. Then, we propose an inexact Newton method to solve the associated nonlinear inverse problems, where any linearized step is solved by a L p Banach space iterative regularization method which acts on the dual space L p* . Indeed, it is well known that regularization in special Banach spaces, such us L p with 1 < p < 2, allows to promote sparsity and to reduce Gibbs phenomena and over-smoothness. Preliminary results concerning numerically computed field data are shown. (paper)
Inverse Problems in a Bayesian Setting
Matthies, Hermann G.
2016-02-13
In a Bayesian setting, inverse problems and uncertainty quantification (UQ)—the propagation of uncertainty through a computational (forward) model—are strongly connected. In the form of conditional expectation the Bayesian update becomes computationally attractive. We give a detailed account of this approach via conditional approximation, various approximations, and the construction of filters. Together with a functional or spectral approach for the forward UQ there is no need for time-consuming and slowly convergent Monte Carlo sampling. The developed sampling-free non-linear Bayesian update in form of a filter is derived from the variational problem associated with conditional expectation. This formulation in general calls for further discretisation to make the computation possible, and we choose a polynomial approximation. After giving details on the actual computation in the framework of functional or spectral approximations, we demonstrate the workings of the algorithm on a number of examples of increasing complexity. At last, we compare the linear and nonlinear Bayesian update in form of a filter on some examples.
PREFACE: International Conference on Inverse Problems 2010
Hon, Yiu-Chung; Ling, Leevan
2011-03-01
Following the first International Conference on Inverse Problems - Recent Theoretical Development and Numerical Approaches held at the City University of Hong Kong in 2002, the fifth International Conference was held again at the City University during December 13-17, 2010. This fifth conference was jointly organized by Professor Yiu-Chung Hon (Co-Chair, City University of Hong Kong, HKSAR), Dr Leevan Ling (Co-Chair, Hong Kong Baptist University, HKSAR), Professor Jin Cheng (Fudan University, China), Professor June-Yub Lee (Ewha Womans University, South Korea), Professor Gui-Rong Liu (University of Cincinnati, USA), Professor Jenn-Nan Wang (National Taiwan University, Taiwan), and Professor Masahiro Yamamoto (The University of Tokyo, Japan). It was agreed to alternate holding the conference among the above places (China, Japan, Korea, Taiwan, and Hong Kong) once every two years. The next conference has been scheduled to be held at the Southeast University (Nanjing, China) in 2012. The purpose of this series of conferences is to establish a strong collaborative link among the universities of the Asian-Pacific regions and worldwide leading researchers in inverse problems. The conference addressed both theoretical (mathematics), applied (engineering) and developmental aspects of inverse problems. The conference was intended to nurture Asian-American-European collaborations in the evolving interdisciplinary areas and it was envisioned that the conference would lead to long-term commitments and collaborations among the participating countries and researchers. There was a total of more than 100 participants. A call for the submission of papers was sent out after the conference, and a total of 19 papers were finally accepted for publication in this proceedings. The papers included in the proceedings cover a wide scope, which reflects the current flourishing theoretical and numerical research into inverse problems. Finally, as the co-chairs of the Inverse Problems
Colloquial and Literary Uses of Inversions. Technical Report No. 217.
Green, Georgia M.
Inversion constructions (declarative sentence constructions in which the subject follows part or all of its verb phrase) are distributed over the whole range of spoken and written language, not along the spoken-written dimension but along a colloquial-literary dimension. Some of these inversions are colloquial or literary for functional reasons,…
Bayesian ISOLA: new tool for automated centroid moment tensor inversion
Czech Academy of Sciences Publication Activity Database
Vackář, J.; Burjánek, Jan; Gallovič, F.; Zahradník, J.; Clinton, J.
2017-01-01
Roč. 210, č. 2 (2017), s. 693-705 ISSN 0956-540X Institutional support: RVO:67985530 Keywords : inverse theory * waveform inversion * computational seismology * earthquake source observations * seismic noise Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 2.414, year: 2016
Application Of Shared Gamma And Inverse-Gaussian Frailty Models ...
African Journals Online (AJOL)
Shared Gamma and Inverse-Gaussian Frailty models are used to analyze the survival times of patients who are clustered according to cancer/tumor types under Parametric Proportional Hazard framework. The result of the ... However, no evidence is strong enough for preference of either Gamma or Inverse Gaussian Frailty.