Bayesian Stratified Sampling to Assess Corpus Utility
Hochberg, J; Thomas, T; Hall, S; Hochberg, Judith; Scovel, Clint; Thomas, Timothy; Hall, Sam
1998-01-01
This paper describes a method for asking statistical questions about a large text corpus. We exemplify the method by addressing the question, "What percentage of Federal Register documents are real documents, of possible interest to a text researcher or analyst?" We estimate an answer to this question by evaluating 200 documents selected from a corpus of 45,820 Federal Register documents. Stratified sampling is used to reduce the sampling uncertainty of the estimate from over 3100 documents to fewer than 1000. The stratification is based on observed characteristics of real documents, while the sampling procedure incorporates a Bayesian version of Neyman allocation. A possible application of the method is to establish baseline statistics used to estimate recall rates for information retrieval systems.
Stratified sampling design based on data mining.
Kim, Yeonkook J; Oh, Yoonhwan; Park, Sunghoon; Cho, Sungzoon; Park, Hayoung
2013-09-01
To explore classification rules based on data mining methodologies which are to be used in defining strata in stratified sampling of healthcare providers with improved sampling efficiency. We performed k-means clustering to group providers with similar characteristics, then, constructed decision trees on cluster labels to generate stratification rules. We assessed the variance explained by the stratification proposed in this study and by conventional stratification to evaluate the performance of the sampling design. We constructed a study database from health insurance claims data and providers' profile data made available to this study by the Health Insurance Review and Assessment Service of South Korea, and population data from Statistics Korea. From our database, we used the data for single specialty clinics or hospitals in two specialties, general surgery and ophthalmology, for the year 2011 in this study. Data mining resulted in five strata in general surgery with two stratification variables, the number of inpatients per specialist and population density of provider location, and five strata in ophthalmology with two stratification variables, the number of inpatients per specialist and number of beds. The percentages of variance in annual changes in the productivity of specialists explained by the stratification in general surgery and ophthalmology were 22% and 8%, respectively, whereas conventional stratification by the type of provider location and number of beds explained 2% and 0.2% of variance, respectively. This study demonstrated that data mining methods can be used in designing efficient stratified sampling with variables readily available to the insurer and government; it offers an alternative to the existing stratification method that is widely used in healthcare provider surveys in South Korea.
Global and Partial Errors in Stratified and Clustering Sampling
Giovanna Nicolini; Anna Lo Presti
2005-01-01
In this paper we split up the sampling error occurred in stratified and clustering sampling, called global error and measured by the variance of estimator, in many partial errors each one referred to a single stratum or cluster. In particular, we study, for clustering sampling, the empirical distribution of the homogeneity coefficient that is very important for settlement of partial errors.
On the Impact of Bootstrap in Stratified Random Sampling
LIU Cheng; ZHAO Lian-wen
2009-01-01
In general the accuracy of mean estimator can be improved by stratified random sampling. In this paper, we provide an idea different from empirical methods that the accuracy can be more improved through bootstrap resampling method under some conditions. The determination of sample size by bootstrap method is also discussed, and a simulation is made to verify the accuracy of the proposed method. The simulation results show that the sample size based on bootstrapping is smaller than that based on central limit theorem.
Atta Ullah
2014-01-01
Full Text Available In practical utilization of stratified random sampling scheme, the investigator meets a problem to select a sample that maximizes the precision of a finite population mean under cost constraint. An allocation of sample size becomes complicated when more than one characteristic is observed from each selected unit in a sample. In many real life situations, a linear cost function of a sample size nh is not a good approximation to actual cost of sample survey when traveling cost between selected units in a stratum is significant. In this paper, sample allocation problem in multivariate stratified random sampling with proposed cost function is formulated in integer nonlinear multiobjective mathematical programming. A solution procedure is proposed using extended lexicographic goal programming approach. A numerical example is presented to illustrate the computational details and to compare the efficiency of proposed compromise allocation.
Stratified source-sampling techniques for Monte Carlo eigenvalue analysis.
Mohamed, A.
1998-07-10
In 1995, at a conference on criticality safety, a special session was devoted to the Monte Carlo ''Eigenvalue of the World'' problem. Argonne presented a paper, at that session, in which the anomalies originally observed in that problem were reproduced in a much simplified model-problem configuration, and removed by a version of stratified source-sampling. In this paper, stratified source-sampling techniques are generalized and applied to three different Eigenvalue of the World configurations which take into account real-world statistical noise sources not included in the model problem, but which differ in the amount of neutronic coupling among the constituents of each configuration. It is concluded that, in Monte Carlo eigenvalue analysis of loosely-coupled arrays, the use of stratified source-sampling reduces the probability of encountering an anomalous result over that if conventional source-sampling methods are used. However, this gain in reliability is substantially less than that observed in the model-problem results.
Sequential stratified sampling belief propagation for multiple targets tracking
无
2006-01-01
Rather than the difficulties of highly non-linear and non-Gaussian observation process and the state distribution in single target tracking, the presence of a large, varying number of targets and their interactions place more challenge on visual tracking. To overcome these difficulties, we formulate multiple targets tracking problem in a dynamic Markov network which consists of three coupled Markov random fields that model the following: a field for joint state of multi-target, one binary process for existence of individual target, and another binary process for occlusion of dual adjacent targets. By introducing two robust functions, we eliminate the two binary processes, and then apply a novel version of belief propagation called sequential stratified sampling belief propagation algorithm to obtain the maximum a posteriori (MAP) estimation in the dynamic Markov network. By using stratified sampler, we incorporate bottom-up information provided by a learned detector (e.g. SVM classifier) and belief information for the messages updating. Other low-level visual cues (e.g. color and shape) can be easily incorporated in our multi-target tracking model to obtain better tracking results. Experimental results suggest that our method is comparable to the state-of-the-art multiple targets tracking methods in several test cases.
Kretzschmar, A; Durand, E; Maisonnasse, A; Vallon, J; Le Conte, Y
2015-06-01
A new procedure of stratified sampling is proposed in order to establish an accurate estimation of Varroa destructor populations on sticky bottom boards of the hive. It is based on the spatial sampling theory that recommends using regular grid stratification in the case of spatially structured process. The distribution of varroa mites on sticky board being observed as spatially structured, we designed a sampling scheme based on a regular grid with circles centered on each grid element. This new procedure is then compared with a former method using partially random sampling. Relative error improvements are exposed on the basis of a large sample of simulated sticky boards (n=20,000) which provides a complete range of spatial structures, from a random structure to a highly frame driven structure. The improvement of varroa mite number estimation is then measured by the percentage of counts with an error greater than a given level.
Sampling scheme optimization from hyperspectral data
Debba, P.
2006-01-01
This thesis presents statistical sampling scheme optimization for geo-environ-menta] purposes on the basis of hyperspectral data. It integrates derived products of the hyperspectral remote sensing data into individual sampling schemes. Five different issues are being dealt with.First, the optimized
Sampling scheme optimization from hyperspectral data
Debba, P.
2006-01-01
This thesis presents statistical sampling scheme optimization for geo-environ-menta] purposes on the basis of hyperspectral data. It integrates derived products of the hyperspectral remote sensing data into individual sampling schemes. Five different issues are being dealt with.First, the optimized
Designing optimal sampling schemes for field visits
Debba, Pravesh
2008-10-01
Full Text Available This is a presentation of a statistical method for deriving optimal spatial sampling schemes. The research focuses on ground verification of minerals derived from hyperspectral data. Spectral angle mapper (SAM) and spectral feature fitting (SFF...
Field sampling scheme optimization using simulated annealing
Debba, Pravesh
2010-10-01
Full Text Available to derive optimal sampling schemes. 2. Hyperspectral remote sensing In the study of electro-magnetic physics, when energy in the form of light interacts with a material, part of the energy at certain wavelength is absorbed, transmitted, emitted... in order to derive optimal sampling schemes. 2. Hyperspectral remote sensing In the study of electro-magnetic physics, when energy in the form of light interacts with a material, part of the energy at certain wavelength is absorbed, transmitted, emitted...
A stratified two-stage sampling design for digital soil mapping in a Mediterranean basin
Blaschek, Michael; Duttmann, Rainer
2015-04-01
ESRI software (ArcGIS) extended by Hawth's Tools and later on its replacement the Geospatial Modelling Environment (GME). 88% of all desired points could actually be reached in the field and have been successfully sampled. Our results indicate that the sampled calibration and validation sets are representative for each other and could be successfully used as interpolation data for spatial prediction purposes. With respect to soil textural fractions, for instance, equal multivariate means and variance homogeneity were found for the two datasets as evidenced by significant (P > 0.05) Hotelling T²-test (2.3 with df1 = 3, df2 = 193) and Bartlett's test statistics (6.4 with df = 6). The multivariate prediction of clay, silt and sand content using a neural network residual cokriging approach reached an explained variance level of 56%, 47% and 63%. Thus, the presented case study is a successful example of considering readily available continuous information on soil forming factors such as geology and relief as stratifying variables for designing sampling schemes in digital soil mapping projects.
A FAMILY OF ESTIMATORS FOR ESTIMATING POPULATION MEAN IN STRATIFIED SAMPLING UNDER NON-RESPONSE
Chaudhary, Manoj K.; RAJESH SINGH; Rakesh K. Shukla; MUKESH KUMAR; FLORENTIN SMARANDACHE
2015-01-01
Khoshnevisan et al. (2007) proposed a general family of estimators for population mean using known value of some population parameters in simple random sampling. The objective of this paper is to propose a family of combined-type estimators in stratified random sampling adapting the family of estimators proposed by Khoshnevisan et al. (2007) under non-response. The properties of proposed family have been discussed. We have also obtained the expressions for optimum sampl...
A FAMILY OF ESTIMATORS FOR ESTIMATING POPULATION MEAN IN STRATIFIED SAMPLING UNDER NON-RESPONSE
Chaudhary, Manoj K.; Rajesh Singh; Rakesh K. Shukla; Mukesh Kumar; Florentin Smarandache
2009-01-01
Khoshnevisan et al. (2007) proposed a general family of estimators for population mean using known value of some population parameters in simple random sampling. The objective of this paper is to propose a family of combined-type estimators in stratified random sampling adapting the family of estimators proposed by Khoshnevisan et al. (2007) under non-response. The properties of proposed family have been discussed. We have also obtained the expressions for optimum sample sizes of the strata i...
Hillson, Roger; Alejandre, Joel D; Jacobsen, Kathryn H; Ansumana, Rashid; Bockarie, Alfred S; Bangura, Umaru; Lamin, Joseph M; Stenger, David A
2015-01-01
There is a need for better estimators of population size in places that have undergone rapid growth and where collection of census data is difficult. We explored simulated estimates of urban population based on survey data from Bo, Sierra Leone, using two approaches: (1) stratified sampling from across 20 neighborhoods and (2) stratified single-stage cluster sampling of only four randomly-sampled neighborhoods. The stratification variables evaluated were (a) occupants per individual residence, (b) occupants per neighborhood, and (c) residential structures per neighborhood. For method (1), stratification variable (a) yielded the most accurate re-estimate of the current total population. Stratification variable (c), which can be estimated from aerial photography and zoning type verification, and variable (b), which could be ascertained by surveying a limited number of households, increased the accuracy of method (2). Small household-level surveys with appropriate sampling methods can yield reasonably accurate estimations of urban populations.
Measurability Aspects of the Compactness Theorem for Sample Compression Schemes
2012-01-01
It was proved in 1998 by Ben-David and Litman that a concept space has a sample compression scheme of size d if and only if every finite subspace has a sample compression scheme of size d. In the compactness theorem, measurability of the hypotheses of the created sample compression scheme is not guaranteed; at the same time measurability of the hypotheses is a necessary condition for learnability. In this thesis we discuss when a sample compression scheme, created from com- pression schemes o...
A FAMILY OF ESTIMATORS FOR ESTIMATING POPULATION MEAN IN STRATIFIED SAMPLING UNDER NON-RESPONSE
Manoj K. Chaudhary
2009-01-01
Full Text Available Khoshnevisan et al. (2007 proposed a general family of estimators for population mean using known value of some population parameters in simple random sampling. The objective of this paper is to propose a family of combined-type estimators in stratified random sampling adapting the family of estimators proposed by Khoshnevisan et al. (2007 under non-response. The properties of proposed family have been discussed. We have also obtained the expressions for optimum sample sizes of the strata in respect to cost of the survey. Results are also supported by numerical analysis.
Chang, Chih-Hao; Liou, Meng-Sing
2007-07-01
In this paper, we propose a new approach to compute compressible multifluid equations. Firstly, a single-pressure compressible multifluid model based on the stratified flow model is proposed. The stratified flow model, which defines different fluids in separated regions, is shown to be amenable to the finite volume method. We can apply the conservation law to each subregion and obtain a set of balance equations . Secondly, the AUSM + scheme, which is originally designed for the compressible gas flow, is extended to solve compressible liquid flows. By introducing additional dissipation terms into the numerical flux, the new scheme, called AUSM +-up, can be applied to both liquid and gas flows. Thirdly, the contribution to the numerical flux due to interactions between different phases is taken into account and solved by the exact Riemann solver. We will show that the proposed approach yields an accurate and robust method for computing compressible multiphase flows involving discontinuities, such as shock waves and fluid interfaces. Several one-dimensional test problems are used to demonstrate the capability of our method, including the Ransom's water faucet problem and the air-water shock tube problem. Finally, several two dimensional problems will show the capability to capture enormous details and complicated wave patterns in flows having large disparities in the fluid density and velocities, such as interactions between water shock wave and air bubble, between air shock wave and water column(s), and underwater explosion. However, conservative form is lost in these balance equations when considering each individual phase; in fact, the interactions that exist simultaneously in both phases manifest themselves as nonconservative terms.
Using remote sensing images to design optimal field sampling schemes
Debba, Pravesh
2008-08-01
Full Text Available At this presentation, the author discussed a statistical method for deriving optimal spatial sampling schemes. First I focus on ground verification of minerals derived from hyperspectral data. Spectral angle mapper (SAM) and spectral feature fitting...
Optimal sampling schemes for vegetation and geological field visits
Debba, Pravesh
2012-07-01
Full Text Available The presentation made to Wits Statistics Department was on common classification methods used in the field of remote sensing, and the use of remote sensing to design optimal sampling schemes for field visits with applications in vegetation...
Accelerated failure time model under general biased sampling scheme.
Kim, Jane Paik; Sit, Tony; Ying, Zhiliang
2016-07-01
Right-censored time-to-event data are sometimes observed from a (sub)cohort of patients whose survival times can be subject to outcome-dependent sampling schemes. In this paper, we propose a unified estimation method for semiparametric accelerated failure time models under general biased estimating schemes. The proposed estimator of the regression covariates is developed upon a bias-offsetting weighting scheme and is proved to be consistent and asymptotically normally distributed. Large sample properties for the estimator are also derived. Using rank-based monotone estimating functions for the regression parameters, we find that the estimating equations can be easily solved via convex optimization. The methods are confirmed through simulations and illustrated by application to real datasets on various sampling schemes including length-bias sampling, the case-cohort design and its variants. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Predominantly Low Metallicities Measured in a Stratified Sample of Lyman Limit Systems at z=3.7
Glidden, Ana; Cooksey, Kathy L; Simcoe, Robert A; O'Meara, John M
2016-01-01
We analyzed metallicities for 33 z=3.4-4.2 absorption line systems with large neutral hydrogen column densities, drawn from a sample of H I-selected of Lyman limit systems (LLSs) identified in Sloan Digital Sky Survey (SDSS) quasar spectra, and stratified based on metal line features. We obtained higher-resolution spectra with the Keck Echellette Spectrograph and Imager (ESI), selecting targets according to our stratification scheme in an effort to fully sample the LLS population metallicity distribution. We established a plausible range of H I column densities and measured the metal column densities (or limits) for ions of carbon, silicon, and aluminum. With simulations, we found ionization-corrected metallicities or upper limits, when appropriate. Interestingly, our ionization models were better constrained with enhanced {\\alpha}-to-aluminum abundances, with a median abundance ratio of [{\\alpha}/Al]=0.3. Measured metallicities were generally low, ranging from [M/H]=-3 to -1.68, with even lower metallicities...
Huang, S.R. [Feng Chia Univ., Taichung (Taiwan, Province of China). Electrical Engineering Dept.
1997-03-01
A combined Monte Carlo and optimum stratified sampling method is presented to better estimate copper loss of a transmission system during a prespecified future period. This design seeks to enhance the precision of copper loss of transmission system estimation, while reducing computation time. The techniques included are optimum stratified sampling and separate ratio estimation. The optimum stratification rule aims to remove any judgemental input and to render the stratification process entirely mechanistic. The estimator, provided by ratio statistics of the sample, can avoid identification of the regression model and thus save computation time. The effectiveness of precision improvement is demonstrated. (UK)
STUDY ON SAMPLING INSPECTION SCHEME TO DIGITAL PRODUCTS IN GIS
无
2001-01-01
Adopting a principle of “check-accept for the f irstrank,inspection for the second rank”,this paper briefly discusses the rati onale of the sampling inspection and the sampling inspection schemes to digital products in GIS.The OC curve is drawn to explain the deficiency of the percent s ampling inspection.Meanwhile,the method of One Time Limiting Quality of count se lection is presented as the inspection scheme for production departments while t he method of One Time After-inspection Mean Percent Defective Upper Limit of cou nt selection is for acceptance departments.
Jiang Houlong
2016-01-01
Full Text Available Sampling methods are important factors that can potentially limit the accuracy of predictions of spatial distribution patterns. A 10 ha tobacco-planted field was selected to compared the accuracy in predicting the spatial distribution of soil properties by using ordinary kriging and cross validation methods between grid sampling and simple random sampling scheme (SRS. To achieve this objective, we collected soil samples from the topsoil (0-20 cm in March 2012. Sample numbers of grid sampling and SRS were both 115 points each. Accuracies of spatial interpolation using the two sampling schemes were then evaluated based on validation samples (36 points and deviations of the estimates. The results suggested that soil pH and nitrate-N (NO3-N had low variation, whereas all other soil properties exhibited medium variation. Soil pH, organic matter (OM, total nitrogen (TN, cation exchange capacity (CEC, total phosphorus (TP and available phosphorus (AP matched the spherical model, whereas the remaining variables fit an exponential model with both sampling methods. The interpolation error of soil pH, TP, and AP was the lowest in SRS. The errors of interpolation for OM, CEC, TN, available potassium (AK and total potassium (TK were the lowest for grid sampling. The interpolation precisions of the soil NO3-N showed no significant differences between the two sampling schemes. Considering our data on interpolation precision and the importance of minerals for cultivation of flue-cured tobacco, the grid-sampling scheme should be used in tobacco-planted fields to determine the spatial distribution of soil properties. The grid-sampling method can be applied in a practical and cost-effective manner to facilitate soil sampling in tobacco-planted field.
Øren Anita
2008-12-01
Full Text Available Abstract Background Prior studies on the impact of problem gambling in the family mainly include help-seeking populations with small numbers of participants. The objective of the present stratified probability sample study was to explore the epidemiology of problem gambling in the family in the general population. Methods Men and women 16–74 years-old randomly selected from the Norwegian national population database received an invitation to participate in this postal questionnaire study. The response rate was 36.1% (3,483/9,638. Given the lack of validated criteria, two survey questions ("Have you ever noticed that a close relative spent more and more money on gambling?" and "Have you ever experienced that a close relative lied to you about how much he/she gambles?" were extrapolated from the Lie/Bet Screen for pathological gambling. Respondents answering "yes" to both questions were defined as Concerned Significant Others (CSOs. Results Overall, 2.0% of the study population was defined as CSOs. Young age, female gender, and divorced marital status were factors positively associated with being a CSO. CSOs often reported to have experienced conflicts in the family related to gambling, worsening of the family's financial situation, and impaired mental and physical health. Conclusion Problematic gambling behaviour not only affects the gambling individual but also has a strong impact on the quality of life of family members.
Vollert, Jan; Maier, Christoph; Attal, Nadine; Bennett, David L.H.; Bouhassira, Didier; Enax-Krumova, Elena K.; Finnerup, Nanna B.; Freynhagen, Rainer; Gierthmühlen, Janne; Haanpää, Maija; Hansson, Per; Hüllemann, Philipp; Jensen, Troels S.; Magerl, Walter; Ramirez, Juan D.; Rice, Andrew S.C.; Schuh-Hofer, Sigrid; Segerdahl, Märta; Serra, Jordi; Shillo, Pallai R.; Sindrup, Soeren; Tesfaye, Solomon; Themistocleous, Andreas C.; Tölle, Thomas R.; Treede, Rolf-Detlef; Baron, Ralf
2017-01-01
Abstract In a recent cluster analysis, it has been shown that patients with peripheral neuropathic pain can be grouped into 3 sensory phenotypes based on quantitative sensory testing profiles, which are mainly characterized by either sensory loss, intact sensory function and mild thermal hyperalgesia and/or allodynia, or loss of thermal detection and mild mechanical hyperalgesia and/or allodynia. Here, we present an algorithm for allocation of individual patients to these subgroups. The algorithm is nondeterministic—ie, a patient can be sorted to more than one phenotype—and can separate patients with neuropathic pain from healthy subjects (sensitivity: 78%, specificity: 94%). We evaluated the frequency of each phenotype in a population of patients with painful diabetic polyneuropathy (n = 151), painful peripheral nerve injury (n = 335), and postherpetic neuralgia (n = 97) and propose sample sizes of study populations that need to be screened to reach a subpopulation large enough to conduct a phenotype-stratified study. The most common phenotype in diabetic polyneuropathy was sensory loss (83%), followed by mechanical hyperalgesia (75%) and thermal hyperalgesia (34%, note that percentages are overlapping and not additive). In peripheral nerve injury, frequencies were 37%, 59%, and 50%, and in postherpetic neuralgia, frequencies were 31%, 63%, and 46%. For parallel study design, either the estimated effect size of the treatment needs to be high (>0.7) or only phenotypes that are frequent in the clinical entity under study can realistically be performed. For crossover design, populations under 200 patients screened are sufficient for all phenotypes and clinical entities with a minimum estimated treatment effect size of 0.5. PMID:28595241
Petraki, Ioanna; Arkoudis, Chrisoula; Terzidis, Agis; Smyrnakis, Emmanouil; Benos, Alexis; Panagiotopoulos, Takis
2017-01-01
Abstract Background: Research on Roma health is fragmentary as major methodological obstacles often exist. Reliable estimates on vaccination coverage of Roma children at a national level and identification of risk factors for low coverage could play an instrumental role in developing evidence-based policies to promote vaccination in this marginalized population group. Methods: We carried out a national vaccination coverage survey of Roma children. Thirty Roma settlements, stratified by geographical region and settlement type, were included; 7–10 children aged 24–77 months were selected from each settlement using systematic sampling. Information on children’s vaccination coverage was collected from multiple sources. In the analysis we applied weights for each stratum, identified through a consensus process. Results: A total of 251 Roma children participated in the study. A vaccination document was presented for the large majority (86%). We found very low vaccination coverage for all vaccines. In 35–39% of children ‘minimum vaccination’ (DTP3 and IPV2 and MMR1) was administered, while 34–38% had received HepB3 and 31–35% Hib3; no child was vaccinated against tuberculosis in the first year of life. Better living conditions and primary care services close to Roma settlements were associated with higher vaccination indices. Conclusions: Our study showed inadequate vaccination coverage of Roma children in Greece, much lower than that of the non-minority child population. This serious public health challenge should be systematically addressed, or, amid continuing economic recession, the gap may widen. Valid national estimates on important characteristics of the Roma population can contribute to planning inclusion policies. PMID:27694159
Jian-Gao Fan; Xiao-Bu Cai; Lui Li; Xing-Jian Li; Fei Dai; Jun Zhu
2008-01-01
AIM: To examine the relations of alcohol consumption to the prevalence of metabolic syndrome in Shanghai adults.METHODS: We performed a cross-sectional analysis of data from the randomized multistage stratified cluster sampling of Shanghai adults, who were evaluated for alcohol consumption and each component of metabolic syndrome, using the adapted U.S. National Cholesterol Education Program criteria. Current alcohol consumption was defined as more than once of alcohol drinking per month.RESULTS: The study population consisted of 3953participants (1524 men) with a mean age of 54.3 ± 12.1years. Among them, 448 subjects (11.3%) were current alcohol drinkers, including 405 males and 43 females.After adjustment for age and sex, the prevalence of current alcohol drinking and metabolic syndrome in the general population of Shanghai was 13.0% and 15.3%,respectively. Compared with nondrinkers, the prevalence of hypertriglyceridemia and hypertension was higher while the prevalence of abdominal obesity, low serum high-density-lipoprotein cholesterol (HDL-C) and diabetes mellitus was lower in subjects who consumed alcohol twice or more per month, with a trend toward reducing the prevalence of metabolic syndrome. Among the current alcohol drinkers, systolic blood pressure, HDL-C, fasting plasma glucose, and prevalence of hypertriglyceridemia tended to increase with increased alcohol consumption.However, Iow-density-lipoprotein cholesterol concentration,prevalence of abdominal obesity, low serum HDL-C andmetabolic syndrome showed the tendency to decrease.Moreover, these statistically significant differences were independent of gender and age.CONCLUSION: Current alcohol consumption is associatedwith a lower prevalence of metabolic syndrome irrespe-ctive of alcohol intake (g/d), and has a favorable influence on HDL-C, waist circumference, and possible diabetes mellitus. However, alcohol intake increases the likelihoodof hypertension, hypertriglyceridemia and hyperglycemia
Tim A. Moore
2016-01-01
Full Text Available DOI: 10.17014/ijog.3.1.29-51Stratified sampling of coal seams for petrographic analysis using block samples is a viable alternative to standard methods of channel sampling and particulate pellet mounts. Although petrographic analysis of particulate pellets is employed widely, it is both time consuming and does not allow variation within sampling units to be assessed - an important measure in any study whether it be for paleoenvironmental reconstruction or in obtaining estimates of industrial attributes. Also, samples taken as intact blocks provide additional information, such as texture and botanical affinity that cannot be gained using particulate pellets. Stratified sampling can be employed both on ‘fine’ and ‘coarse’ grained coal units. Fine-grained coals are defined as those coal intervals that do not contain vitrain bands greater than approximately 1 mm in thickness (as measured perpendicular to bedding. In fine-grained coal seams, a reasonable sized block sample (with a polished surface area of ~3 cm2 can be taken that encapsulates the macroscopic variability. However, for coarse-grained coals (vitrain bands >1 mm a different system has to be employed in order to accurately account for the larger particles. Macroscopic point counting of vitrain bands can accurately account for those particles>1 mm within a coal interval. This point counting method is conducted using something as simple as string on a coal face with marked intervals greater than the largest particle expected to be encountered (although new technologies are being developed to capture this type of information digitally. Comparative analyses of particulate pellets and blocks on the same interval show less than 6% variation between the two sample types when blocks are recalculated to include macroscopic counts of vitrain. Therefore even in coarse-grained coals, stratified sampling can be used effectively and representatively.
Lydia Leonardo
2012-01-01
Full Text Available For the first time in the country, a national baseline prevalence survey using a well-defined sampling design such as a stratified two-step systematic cluster sampling was conducted in 2005 to 2008. The purpose of the survey was to stratify the provinces according to prevalence of schistosomiasis such as high, moderate, and low prevalence which in turn would be used as basis for the intervention program to be implemented. The national survey was divided into four phases. Results of the first two phases conducted in Mindanao and the Visayas were published in 2008. Data from the last two phases showed three provinces with prevalence rates higher than endemic provinces surveyed in the first two phases thus changing the overall ranking of endemic provinces at the national level. Age and sex distribution of schistosomiasis remained the same in Luzon and Maguindanao. Soil-transmitted and food-borne helminthes were also recorded in these surveys. This paper deals with the results of the last 2 phases done in Luzon and Maguindanao and integrates all four phases in the discussion.
Sutor, Malinda M.; Dagg, Michael J.
2008-06-01
The effects of vertical sampling resolution on estimates of plankton biomass and grazing calculations were examined using data collected in two different areas with vertically stratified water columns. Data were collected from one site in the upwelling region off Oregon and from four sites in the Northern Gulf of Mexico, three within the Mississippi River plume and one in adjacent oceanic waters. Plankton were found to be concentrated in discrete layers with sharp vertical gradients at all the stations. Phytoplankton distributions were correlated with gradients in temperature and salinity, but microzooplankton and mesozooplankton distributions were not. Layers of zooplankton were sometimes collocated with layers of phytoplankton, but this was not always the case. Simulated calculations demonstrate that when averages are taken over the water column, or coarser scale vertical sampling resolution is used, biomass and mesozooplankton grazing and filtration rates can be greatly underestimated. This has important implications for understanding the ecological significance of discrete layers of plankton and for assessing rates of grazing and production in stratified water columns.
Leonardo, Lydia; Rivera, Pilarita; Saniel, Ofelia; Villacorte, Elena; Lebanan, May Antonnette; Crisostomo, Bobby; Hernandez, Leda; Baquilod, Mario; Erce, Edgardo; Martinez, Ruth; Velayudhan, Raman
2012-01-01
For the first time in the country, a national baseline prevalence survey using a well-defined sampling design such as a stratified two-step systematic cluster sampling was conducted in 2005 to 2008. The purpose of the survey was to stratify the provinces according to prevalence of schistosomiasis such as high, moderate, and low prevalence which in turn would be used as basis for the intervention program to be implemented. The national survey was divided into four phases. Results of the first two phases conducted in Mindanao and the Visayas were published in 2008. Data from the last two phases showed three provinces with prevalence rates higher than endemic provinces surveyed in the first two phases thus changing the overall ranking of endemic provinces at the national level. Age and sex distribution of schistosomiasis remained the same in Luzon and Maguindanao. Soil-transmitted and food-borne helminthes were also recorded in these surveys. This paper deals with the results of the last 2 phases done in Luzon and Maguindanao and integrates all four phases in the discussion.
A. Martín Andrés
2015-01-01
Full Text Available The Mantel-Haenszel test is the most frequent asymptotic test used for analyzing stratified 2 × 2 tables. Its exact alternative is the test of Birch, which has recently been reconsidered by Jung. Both tests have a conditional origin: Pearson’s chi-squared test and Fisher’s exact test, respectively. But both tests have the same drawback that the result of global test (the stratified test may not be compatible with the result of individual tests (the test for each stratum. In this paper, we propose to carry out the global test using a multiple comparisons method (MC method which does not have this disadvantage. By refining the method (MCB method an alternative to the Mantel-Haenszel and Birch tests may be obtained. The new MC and MCB methods have the advantage that they may be applied from an unconditional view, a methodology which until now has not been applied to this problem. We also propose some sample size calculation methods.
Khewal Bhupendra Kesur
2013-01-01
Full Text Available This paper examines the application of Latin Hypercube Sampling (LHS and Antithetic Variables (AVs to reduce the variance of estimated performance measures from microscopic traffic simulators. LHS and AV allow for a more representative coverage of input probability distributions through stratification, reducing the standard error of simulation outputs. Two methods of implementation are examined, one where stratification is applied to headways and routing decisions of individual vehicles and another where vehicle counts and entry times are more evenly sampled. The proposed methods have wider applicability in general queuing systems. LHS is found to outperform AV, and reductions of up to 71% in the standard error of estimates of traffic network performance relative to independent sampling are obtained. LHS allows for a reduction in the execution time of computationally expensive microscopic traffic simulators as fewer simulations are required to achieve a fixed level of precision with reductions of up to 84% in computing time noted on the test cases considered. The benefits of LHS are amplified for more congested networks and as the required level of precision increases.
Diffusion spectrum MRI using body-centered-cubic and half-sphere sampling schemes.
Kuo, Li-Wei; Chiang, Wen-Yang; Yeh, Fang-Cheng; Wedeen, Van Jay; Tseng, Wen-Yih Isaac
2013-01-15
The optimum sequence parameters of diffusion spectrum MRI (DSI) on clinical scanners were investigated previously. However, the scan time of approximately 30 min is still too long for patient studies. Additionally, relatively large sampling interval in the diffusion-encoding space may cause aliasing artifact in the probability density function when Fourier transform is undertaken, leading to estimation error in fiber orientations. Therefore, this study proposed a non-Cartesian sampling scheme, body-centered-cubic (BCC), to avoid the aliasing artifact as compared to the conventional Cartesian grid sampling scheme (GRID). Furthermore, the accuracy of DSI with the use of half-sphere sampling schemes, i.e. GRID102 and BCC91, was investigated by comparing to their full-sphere sampling schemes, GRID203 and BCC181, respectively. In results, smaller deviation angle and lower angular dispersion were obtained by using the BCC sampling scheme. The half-sphere sampling schemes yielded angular precision and accuracy comparable to the full-sphere sampling schemes. The optimum b(max) was approximately 4750 s/mm(2) for GRID and 4500 s/mm(2) for BCC. In conclusion, the BCC sampling scheme could be implemented as a useful alternative to the GRID sampling scheme. Combination of BCC and half-sphere sampling schemes, that is BCC91, may potentially reduce the scan time of DSI from 30 min to approximately 14 min while maintaining its precision and accuracy. Copyright © 2012 Elsevier B.V. All rights reserved.
Sah, B. P.; Hämäläinen, J. M.; Sah, A. K.; Honji, K.; Foli, E. G.; Awudi, C.
2012-07-01
Accurate and reliable estimation of biomass in tropical forest has been a challenging task because a large proportion of forests are difficult to access or inaccessible. So, for effective implementation of REDD+ and fair benefit sharing, the proper designing of field plot sampling schemes plays a significant role in achieving robust biomass estimation. The existing forest inventory protocols using various field plot sampling schemes, including FAO's regular grid concept of sampling for land cover inventory at national level, are time and human resource intensive. Wall to wall LiDAR scanning is, however, a better approach to assess biomass with high precision and spatial resolution even though this approach suffers from high costs. Considering the above, in this study a sampling design based on a LiDAR strips sampling scheme has been devised for Ghanaian forests to support field plot sampling. Using Top-of-Atmosphere (TOA) reflectance value of satellite data, Land Use classification was carried out in accordance with IPCC definitions and the resulting classes were further stratified, incorporating existing GIS data of ecological zones in the study area. Employing this result, LiDAR sampling strips were allocated using systematic sampling techniques. The resulting LiDAR strips represented all forest categories, as well as other Land Use classes, with their distribution adequately representing the areal share of each category. In this way, out of at total area of 15,153km2 of the study area, LiDAR scanning was required for only 770 km2 (sampling intensity being 5.1%). We conclude that this systematic LiDAR sampling design is likely to adequately cover variation in above-ground biomass densities and serve as sufficient a-priori data, together with the Land Use classification produced, for designing efficient field plot sampling over the seven ecological zones.
Bhatia, Triptish; Gettig, Elizabeth A; Gottesman, Irving I; Berliner, Jonathan; Mishra, N N; Nimgaonkar, Vishwajit L; Deshpande, Smita N
2016-12-01
Schizophrenia (SZ) has an estimated heritability of 64-88%, with the higher values based on twin studies. Conventionally, family history of psychosis is the best individual-level predictor of risk, but reliable risk estimates are unavailable for Indian populations. Genetic, environmental, and epigenetic factors are equally important and should be considered when predicting risk in 'at risk' individuals. To estimate risk based on an Indian schizophrenia participant's family history combined with selected demographic factors. To incorporate variables in addition to family history, and to stratify risk, we constructed a regression equation that included demographic variables in addition to family history. The equation was tested in two independent Indian samples: (i) an initial sample of SZ participants (N=128) with one sibling or offspring; (ii) a second, independent sample consisting of multiply affected families (N=138 families, with two or more sibs/offspring affected with SZ). The overall estimated risk was 4.31±0.27 (mean±standard deviation). There were 19 (14.8%) individuals in the high risk group, 75 (58.6%) in the moderate risk and 34 (26.6%) in the above average risk (in Sample A). In the validation sample, risks were distributed as: high (45%), moderate (38%) and above average (17%). Consistent risk estimates were obtained from both samples using the regression equation. Familial risk can be combined with demographic factors to estimate risk for SZ in India. If replicated, the proposed stratification of risk may be easier and more realistic for family members. Copyright © 2016. Published by Elsevier B.V.
An Optimization-Based Sampling Scheme for Phylogenetic Trees
Misra, Navodit; Blelloch, Guy; Ravi, R.; Schwartz, Russell
Much modern work in phylogenetics depends on statistical sampling approaches to phylogeny construction to estimate probability distributions of possible trees for any given input data set. Our theoretical understanding of sampling approaches to phylogenetics remains far less developed than that for optimization approaches, however, particularly with regard to the number of sampling steps needed to produce accurate samples of tree partition functions. Despite the many advantages in principle of being able to sample trees from sophisticated probabilistic models, we have little theoretical basis for concluding that the prevailing sampling approaches do in fact yield accurate samples from those models within realistic numbers of steps. We propose a novel approach to phylogenetic sampling intended to be both efficient in practice and more amenable to theoretical analysis than the prevailing methods. The method depends on replacing the standard tree rearrangement moves with an alternative Markov model in which one solves a theoretically hard but practically tractable optimization problem on each step of sampling. The resulting method can be applied to a broad range of standard probability models, yielding practical algorithms for efficient sampling and rigorous proofs of accurate sampling for some important special cases. We demonstrate the efficiency and versatility of the method in an analysis of uncertainty in tree inference over varying input sizes. In addition to providing a new practical method for phylogenetic sampling, the technique is likely to prove applicable to many similar problems involving sampling over combinatorial objects weighted by a likelihood model.
Control charts for location based on different sampling schemes
Mehmood, R.; Riaz, M.; Does, R.J.M.M.
2013-01-01
Control charts are the most important statistical process control tool for monitoring variations in a process. A number of articles are available in the literature for the X̄ control chart based on simple random sampling, ranked set sampling, median-ranked set sampling (MRSS), extreme-ranked set
Bates, Alice P; Kennedy, Rodney A
2015-01-01
We propose a sampling scheme on the sphere and develop a corresponding spherical harmonic transform (SHT) for the accurate reconstruction of the diffusion signal in diffusion magnetic resonance imaging (dMRI). By exploiting the antipodal symmetry, we design a sampling scheme that requires the optimal number of samples on the sphere, equal to the degrees of freedom required to represent the antipodally symmetric band-limited diffusion signal in the spectral (spherical harmonic) domain. Compared with existing sampling schemes on the sphere that allow for the accurate reconstruction of the diffusion signal, the proposed sampling scheme reduces the number of samples required by a factor of two or more. We analyse the numerical accuracy of the proposed SHT and show through experiments that the proposed sampling allows for the accurate and rotationally invariant computation of the SHT to near machine precision accuracy.
Elizabeth A. Freeman; Gretchen G. Moisen; Tracy S. Frescino
2012-01-01
Random Forests is frequently used to model species distributions over large geographic areas. Complications arise when data used to train the models have been collected in stratified designs that involve different sampling intensity per stratum. The modeling process is further complicated if some of the target species are relatively rare on the landscape leading to an...
NOTE: Sampling and reconstruction schemes for biomagnetic sensor arrays
Naddeo, Adele; Della Penna, Stefania; Nappi, Ciro; Vardaci, Emanuele; Pizzella, Vittorio
2002-09-01
In this paper we generalize the approach of Ahonen et al (1993 IEEE Trans. Biomed. Eng. 40 859-69) to two-dimensional non-uniform sampling. The focus is on two main topics: (1) searching for the optimal sensor configuration on a planar measurement surface; and (2) reconstructing the magnetic field (a continuous function) from a discrete set of data points recorded with a finite number of sensors. A reconstruction formula for Bz is derived in the framework of the multidimensional Papoulis generalized sampling expansion (Papoulis A 1977 IEEE Trans. Circuits Syst. 24 652-4, Cheung K F 1993 Advanced Topics in Shannon Sampling and Interpolation Theory (New York: Springer) pp 85-119) in a particular case. Application of these considerations to the design of biomagnetic sensor arrays is also discussed.
Sampling and reconstruction schemes for biomagnetic sensor arrays.
Naddeo, Adele; Della Penna, Stefania; Nappi, Ciro; Vardaci, Emanuele; Pizzella, Vittorio
2002-09-21
In this paper we generalize the approach of Ahonen et al (1993 IEEE Trans. Biomed. Eng. 40 859-69) to two-dimensional non-uniform sampling. The focus is on two main topics: (1) searching for the optimal sensor configuration on a planar measurement surface; and (2) reconstructing the magnetic field (a continuous function) from a discrete set of data points recorded with a finite number of sensors. A reconstruction formula for Bz is derived in the framework of the multidimensional Papoulis generalized sampling expansion (Papoulis A 1977 IEEE Trans. Circuits Syst. 24 652-4, Cheung K F 1993 Advanced Topics in Shannon Sampling and Interpolation Theory (New York: Springer) pp 85-119) in a particular case. Application of these considerations to the design of biomagnetic sensor arrays is also discussed.
Rare-event simulation for tandem queues: A simple and efficient importance sampling scheme
Miretskiy, D.; Scheinhardt, W.; Mandjes, M.
2009-01-01
This paper focuses on estimating the rare event of overflow in the downstream queue of a tandem Jackson queue, relying on importance sampling. It is known that in this setting ‘traditional’ state-independent schemes perform poorly. More sophisticated state-dependent schemes yield asymptotic efficien
Debba, Pravesh
2009-07-01
Full Text Available guest at Nelson Mandela Metropolitan University presents a prospective and retrospective optimal spatial sampling scheme using the spatial distribution of secondary iron-bearing oxides/hydroxides, to characterize a mine tailings area....
Gener Tadeu Pereira
2013-10-01
Full Text Available The sampling scheme is essential in the investigation of the spatial variability of soil properties in Soil Science studies. The high costs of sampling schemes optimized with additional sampling points for each physical and chemical soil property, prevent their use in precision agriculture. The purpose of this study was to obtain an optimal sampling scheme for physical and chemical property sets and investigate its effect on the quality of soil sampling. Soil was sampled on a 42-ha area, with 206 geo-referenced points arranged in a regular grid spaced 50 m from each other, in a depth range of 0.00-0.20 m. In order to obtain an optimal sampling scheme for every physical and chemical property, a sample grid, a medium-scale variogram and the extended Spatial Simulated Annealing (SSA method were used to minimize kriging variance. The optimization procedure was validated by constructing maps of relative improvement comparing the sample configuration before and after the process. A greater concentration of recommended points in specific areas (NW-SE direction was observed, which also reflects a greater estimate variance at these locations. The addition of optimal samples, for specific regions, increased the accuracy up to 2 % for chemical and 1 % for physical properties. The use of a sample grid and medium-scale variogram, as previous information for the conception of additional sampling schemes, was very promising to determine the locations of these additional points for all physical and chemical soil properties, enhancing the accuracy of kriging estimates of the physical-chemical properties.
Credit-based accept-zero sampling schemes for the control of outgoing quality
Baillie, David H.; Klaassen, Chris A.J.
2000-01-01
A general procedure is presented for switching between accept-zero attributes or variables sampling plans to provide acceptance sampling schemes with a specified limit on the (suitably defined) average outgoing quality (AOQ). The switching procedure is based on credit, defined as the total number of
LI Yan; SHI Zhou; WU Ci-fang; LI Feng; LI Hong-yi
2007-01-01
The acquisition of precise soil data representative of the entire survey area,is a critical issue for many treatments such as irrigation or fertilization in precision agriculture.The aim of this study was to investigate the spatial variability of soil bulk electrical conductivity(ECb)in a coastal saline field and design an optimized spatial sampling scheme of ECb based on a sampling design algorithm,the variance quad-tree(VQT)method.Soil ECb data were collected from the field at 20m interval in a regular grid scheme.The smooth contour map of the whole field was obtained by ordinary kriging interpolation,VQT algorithm was then used to split the smooth contour map into strata of different number desired,the sampling locations can be selected within each stratum in subsequent sampling.The result indicated that the probability of choosing representative sampling sites was increased significantly by using VQT method with the sampling number being greatly reduced compared to grid sampling design while retaining the same prediction accuracy.The advantage of the VQT method is that this scheme samples sparsely in fields where the spatial variability is relatively uniform and more intensive where the variability is large.Thus the sampling efficiency can be improved,hence facilitate an assessment methodology that can be applied in a rapid,practical and cost-effective manner.
Study on a new meteorological sampling scheme developed for the OSCAAR code system
Liu Xinhe; Tomita, Kenichi; Homma, Toshimitsu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
2002-03-01
One important step in Level-3 Probabilistic Safety Assessment is meteorological sequence sampling, on which the previous studies were mainly related to code systems using the straight-line plume model and more efforts are needed for those using the trajectory puff model such as the OSCAAR code system. This report describes the development of a new meteorological sampling scheme for the OSCAAR code system that explicitly considers population distribution. A group of principles set for the development of this new sampling scheme includes completeness, appropriate stratification, optimum allocation, practicability and so on. In this report, discussions are made about the procedures of the new sampling scheme and its application. The calculation results illustrate that although it is quite difficult to optimize stratification of meteorological sequences based on a few environmental parameters the new scheme do gather the most inverse conditions in a single subset of meteorological sequences. The size of this subset may be as small as a few dozens, so that the tail of a complementary cumulative distribution function is possible to remain relatively static in different trials of the probabilistic consequence assessment code. (author)
Designing sampling schemes for effect monitoring of nutrient leaching from agricultural soils.
Brus, D.J.; Noij, I.G.A.M.
2008-01-01
A general methodology for designing sampling schemes for monitoring is illustrated with a case study aimed at estimating the temporal change of the spatial mean P concentration in the topsoil of an agricultural field after implementation of the remediation measure. A before-after control-impact (BAC
Study on a new meteorological sampling scheme developed for the OSCAAR code system
Liu, X.; 富田 賢一; 本間 俊充
2002-01-01
One important step in Level 3 Probabilistic Safety Assessment is meteorological sequence sampling, on which the previous studies were mainly related to code systems using straight line plume model and more efforts are needed for trajectory puff model such as the OSCAAR code system. This report describes the development of a new meteorological sampling scheme for the OSCAAR code system that explicitly considers population distribution. A group of principles was set forth for the development of...
A Programmable Look-Up Table-Based Interpolator with Nonuniform Sampling Scheme
Élvio Carlos Dutra e Silva Júnior
2012-01-01
Full Text Available Interpolation is a useful technique for storage of complex functions on limited memory space: some few sampling values are stored on a memory bank, and the function values in between are calculated by interpolation. This paper presents a programmable Look-Up Table-based interpolator, which uses a reconfigurable nonuniform sampling scheme: the sampled points are not uniformly spaced. Their distribution can also be reconfigured to minimize the approximation error on specific portions of the interpolated function’s domain. Switching from one set of configuration parameters to another set, selected on the fly from a variety of precomputed parameters, and using different sampling schemes allow for the interpolation of a plethora of functions, achieving memory saving and minimum approximation error. As a study case, the proposed interpolator was used as the core of a programmable noise generator—output signals drawn from different Probability Density Functions were produced for testing FPGA implementations of chaotic encryption algorithms. As a result of the proposed method, the interpolation of a specific transformation function on a Gaussian noise generator reduced the memory usage to 2.71% when compared to the traditional uniform sampling scheme method, while keeping the approximation error below a threshold equal to 0.000030518.
Gall, Heather E.; Jafvert, Chad T.; Jenkinson, Byron
2010-11-01
Automated sample collection for water quality research and evaluation generally is performed by simple time-paced or flow-weighted sampling protocols. However, samples collected on strict time-paced or flow-weighted schemes may not adequately capture all elements of storm event hydrographs (i.e., rise, peak, and recession). This can result in inadequate information for calculating chemical mass flux over storm events. In this research, an algorithm was developed to guide automated sampling of hydrographs based on storm-specific information. A key element of the new "hydrograph-specific sampling scheme" is the use of a hydrograph recession model for predicting the hydrograph recession curve, during which flow-paced intervals are calculated for scheduling the remaining samples. The algorithm was tested at a tile drained Midwest agricultural site where real-time flow data were processed by a programmable datalogger that in turn activated an automated sampler at the appropriate sampling times to collect a total of twenty samples during each storm event independent of the number of sequential hydrographs generated. The utility of the algorithm was successfully tested with hydrograph data collected at both a tile drain and agricultural ditch, suggesting the potential for general applicability of the method. This sampling methodology is flexible in that the logic can be adapted for use with any hydrograph recession model; however, in this case a power law equation proved to be the most practical model.
Effect of Sampling Depth on Air-Sea CO2 Flux Estimates in River-Stratified Arctic Coastal Waters
Miller, L. A.; Papakyriakou, T. N.
2015-12-01
In summer-time Arctic coastal waters that are strongly influenced by river run-off, extreme stratification severely limits wind mixing, making it difficult to effectively sample the surface 'mixed layer', which can be as shallow as 1 m, from a ship. During two expeditions in southwestern Hudson Bay, off the Nelson, Hayes, and Churchill River estuaries, we confirmed that sampling depth has a strong impact on estimates of 'surface' pCO2 and calculated air-sea CO2 fluxes. We determined pCO2 in samples collected from 5 m, using a typical underway system on the ship's seawater supply; from the 'surface' rosette bottle, which was generally between 1 and 3 m; and using a niskin bottle deployed at 1 m and just below the surface from a small boat away from the ship. Our samples confirmed that the error in pCO2 derived from typical ship-board versus small-boat sampling at a single station could be nearly 90 μatm, leading to errors in the calculated air-sea CO2 flux of more than 0.1 mmol/(m2s). Attempting to extrapolate such fluxes over the 6,000,000 km2 area of the Arctic shelves would generate an error approaching a gigamol CO2/s. Averaging the station data over a cruise still resulted in an error of nearly 50% in the total flux estimate. Our results have implications not only for the design and execution of expedition-based sampling, but also for placement of in-situ sensors. Particularly in polar waters, sensors are usually deployed on moorings, well below the surface, to avoid damage and destruction from drifting ice. However, to obtain accurate information on air-sea fluxes in these areas, it is necessary to deploy sensors on ice-capable buoys that can position the sensors in true 'surface' waters.
Komada, Kenichi; Sugiyama, Masaya; Vongphrachanh, Phengta; Xeuatvongsa, Anonh; Khamphaphongphane, Bouaphan; Kitamura, Tomomi; Kiyohara, Tomoko; Wakita, Takaji; Oshitani, Hitoshi; Hachiya, Masahiko
2015-07-01
There is limited information regarding the prevalence of hepatitis B in Lao PDR, where the hepatitis disease burden is substantial. Thus, reliable seroprevalence data is needed for the disease, based on probability sampling. A stratified, multistage, cluster sampling survey of hepatitis B surface antigen (HBsAg) positivity among children aged 5-9 years and their mothers aged 15-45 years was conducted. Participants were selected randomly from the central region of Lao PDR via probability-proportional-to-size sampling. Blood samples were collected onto filter paper and subsequently analyzed using a chemiluminescent microparticle immunoassay. A total of 911 mother-and-child pairs were collected; the seroprevalence of HBsAg was estimated to be 2.1% (95% confidence interval 0.8-3.4%) among children and 4.1% (95% confidence interval 2.6-5.5%) in their mothers after taking into account the sampling design and the weight of each sample. The children's HBsAg positivity was positively associated with maternal infection and being born in a non-health facility, while the maternal infection status was not associated with any background characteristic. Lao PDR has a relatively lower HBsAg prevalence in the general population compared to surrounding countries. To ensure comparability to other countries and to future data, rapid field tests are recommended for a nationwide prevalence survey. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
Valverde Arias, Omar; Valencia, José; Saa Requejo, António; Garrido, Alberto
2017-04-01
Based-index insurance for farming has become in an efficient alternative for farmers to transfer risk to another instances. Actually, in Ecuador, there is a conventional agricultural insurance for rice crop, although it is necessary to develop based-index insurance that could cover more farmers for extreme events with catastrophic consequences. This based-index insurance could consist to estimate crop losses by drought through NDVI (Normalized Difference Vegetation Index). A first step was to establish homogeneous areas based on Principal Component Analysis of soil properties (Valverde et al., 2016) where rice is cultivated. Two main areas were found (f7 and f15) that was based mainly on slope, texture and effective depth. These ones are the sites considered to sampling and study the NDVI. MODIS images of 250x250 m resolution were selected of the study area, Babahoyo canton (Los Rios province, Ecuador), and calculated the NDVI index at rice growth stage in both sites at several years. The number of samples in each site was proportional to the area of cultivated rice. NDVI distribution values were calculated in each homogeneous zones (f7 and f15) through years. Several statistical analysis were performed to investigate the difference between both sites. Results are discussed in the context of based index insurance.
Isabel Eleanor Moore
2015-06-01
Full Text Available Aim: The study aimed to determine the effectiveness of benthic macroinvertebrate dredge net sampling procedures as an alternative method to kick net sampling in tropical freshwater systems, specifically as an evaluation of sampling methods used in the Zambian Invertebrate Scoring System (ZISS river bioassessment scheme. Tropical freshwater ecosystems are sometimes dangerous or inaccessible to sampling teams using traditional kick-sampling methods, so identifying an alternative procedure that produces similar results is necessary in order to collect data from a wide variety of habitats.MethodsBoth kick and dredge nets were used to collect macroinvertebrate samples at 16 riverine sites in Zambia, ranging from backwaters and floodplain lagoons to fast flowing streams and rivers. The data were used to calculate ZISS, diversity (S: number of taxa present, and Average Score Per Taxon (ASPT scores per site, using the two sampling methods to compare their sampling effectiveness. Environmental parameters, namely pH, conductivity, underwater photosynthetically active radiation (PAR, temperature, alkalinity, flow, and altitude, were also recorded and used in statistical analysis. Invertebrate communities present at the sample sites were determined using multivariate procedures.ResultsAnalysis of the invertebrate community and environmental data suggested that the testing exercise was undertaken in four distinct macroinvertebrate community types, supporting at least two quite different macroinvertebrate assemblages, and showing significant differences in habitat conditions. Significant correlations were found for all three bioassessment score variables between results acquired using the two methods, with dredge-sampling normally producing lower scores than did the kick net procedures. Linear regression models were produced in order to correct each biological variable score collected by a dredge net to a score similar to that of one collected by kick net
Miller, Ezer; Huppert, Amit; Novikov, Ilya; Warburg, Alon; Hailu, Asrat; Abbasi, Ibrahim; Freedman, Laurence S
2015-11-10
In this work, we describe a two-stage sampling design to estimate the infection prevalence in a population. In the first stage, an imperfect diagnostic test was performed on a random sample of the population. In the second stage, a different imperfect test was performed in a stratified random sample of the first sample. To estimate infection prevalence, we assumed conditional independence between the diagnostic tests and develop method of moments estimators based on expectations of the proportions of people with positive and negative results on both tests that are functions of the tests' sensitivity, specificity, and the infection prevalence. A closed-form solution of the estimating equations was obtained assuming a specificity of 100% for both tests. We applied our method to estimate the infection prevalence of visceral leishmaniasis according to two quantitative polymerase chain reaction tests performed on blood samples taken from 4756 patients in northern Ethiopia. The sensitivities of the tests were also estimated, as well as the standard errors of all estimates, using a parametric bootstrap. We also examined the impact of departures from our assumptions of 100% specificity and conditional independence on the estimated prevalence. Copyright © 2015 John Wiley & Sons, Ltd.
Greil, Arthur L; McQuillan, Julia; Shreffler, Karina M; Johnson, Katherine M; Slauson-Blevins, Kathleen S
2011-12-01
Evidence of group differences in reproductive control and access to reproductive health care suggests the continued existence of "stratified reproduction" in the United States. Women of color are overrepresented among people with infertility but are underrepresented among those who receive medical services. The authors employ path analysis to uncover mechanisms accounting for these differences among black, Hispanic, Asian, and non-Hispanic white women using a probability-based sample of 2,162 U.S. women. Black and Hispanic women are less likely to receive services than other women. The enabling conditions of income, education, and private insurance partially mediate the relationship between race-ethnicity and receipt of services but do not fully account for the association at all levels of service. For black and Hispanic women, social cues, enabling conditions, and predisposing conditions contribute to disparities in receipt of services. Most of the association between race-ethnicity and service receipt is indirect rather than direct.
Marcos Adami
2010-06-01
Full Text Available O objetivo deste trabalho foi avaliar o desempenho de um modelo probabilístico de amostragem estratificada por pontos, e definir um tamanho de amostra adequado para estimar a área cultivada com soja no Rio Grande do Sul. A área foi estratificada de acordo com a percentagem de soja cultivada em cada município do estado: menor que 20, de 20 a 40 e maior que 40%. Foram avaliadas estimativas obtidas por meio de seis tamanhos de amostras, resultantes da combinação de três níveis de significância (10, 5 e 1% e dois valores de erro amostral (5 e 2,5%. Para cada tamanho de amostra, foram realizados 400 sorteios aleatórios. As estimativas foram avaliadas com base na área de soja obtida de um mapa temático de referência proveniente de uma cuidadosa classificação automática e visual de imagens multitemporais dos satélites TM/Landsat-5 e ETM+/Landsat-7 disponível para a safra 2000/2001. A área de soja no Rio Grande do Sul pode ser estimada por meio de um modelo de amostragem probabilística estratificada por pontos, sendo que a melhor estimativa é obtida para o maior tamanho amostral (1.990 pontos, com diferença de apenas -0,14% em relação à estimativa do mapa de referência e um coeficiente de variação de 6,98%.The objective of this work was to evaluate the performance of a probabilistic sampling model stratified by points and to define an appropriate sample size to estimate the cultivated soybean area in the state of Rio Grande do Sul, Brazil. The area was stratified according to the percentage of soybean cultivated in each state municipality: less than 20, from 20 to 40 and more than 40%. Estimates were evaluated based on six sample sizes, resulting from the combination of three significance levels (10, 5 and 1% and two sampling errors (5 and 2,5%, choosing 400 random samples for each sample size. The estimates were compared to a reference soybean thematic map available for the crop year 2000/2001 that was derived from a careful
Bakri, Barbara; Weimer, Marco; Hauck, Gerrit; Reich, Gabriele
2015-11-01
Scope of the study was (1) to develop a lean quantitative calibration for real-time near-infrared (NIR) blend monitoring, which meets the requirements in early development of pharmaceutical products and (2) to compare the prediction performance of this approach with the results obtained from stratified sampling using a sample thief in combination with off-line high pressure liquid chromatography (HPLC) and at-line near-infrared chemical imaging (NIRCI). Tablets were manufactured from powder blends and analyzed with NIRCI and HPLC to verify the real-time results. The model formulation contained 25% w/w naproxen as a cohesive active pharmaceutical ingredient (API), microcrystalline cellulose and croscarmellose sodium as cohesive excipients and free-flowing mannitol. Five in-line NIR calibration approaches, all using the spectra from the end of the blending process as reference for PLS modeling, were compared in terms of selectivity, precision, prediction accuracy and robustness. High selectivity could be achieved with a "reduced" approach i.e. API and time saving approach (35% reduction of API amount) based on six concentration levels of the API with three levels realized by three independent powder blends and the additional levels obtained by simply increasing the API concentration in these blends. Accuracy and robustness were further improved by combining this calibration set with a second independent data set comprising different excipient concentrations and reflecting different environmental conditions. The combined calibration model was used to monitor the blending process of independent batches. For this model formulation the target concentration of the API could be achieved within 3 min indicating a short blending time. The in-line NIR approach was verified by stratified sampling HPLC and NIRCI results. All three methods revealed comparable results regarding blend end point determination. Differences in both mean API concentration and RSD values could be
ECCM scheme against interrupted sampling repeater jammer based on time-frequency analysis
Shixian Gong; Xizhang Wei; Xiang Li
2014-01-01
The interrupted sampling repeater jamming (ISRJ) is an effective deception jamming method for coherent radar, especial y for the wideband linear frequency modulation (LFM) radar. An electronic counter-countermeasure (ECCM) scheme is proposed to remove the ISRJ-based false targets from the pulse compres-sion result of the de-chirping radar. Through the time-frequency (TF) analysis of the radar echo signal, it can be found that the TF characteristics of the ISRJ signal are discontinuous in the pulse duration because the ISRJ jammer needs short durations to re-ceive the radar signal. Based on the discontinuous characteristics a particular band-pass filter can be generated by two alternative approaches to retain the true target signal and suppress the ISRJ signal. The simulation results prove the validity of the proposed ECCM scheme for the ISRJ.
无
2010-01-01
A hybrid microsystem with separately functioned temperature controlling substrate and sample operating fluidic microchannel was developed to demonstrate a reconfigurable microfluidics scheme.The temperature controlling substrate integrated a micro heater and a temperature sensor by using traditional silicon-based micromechanical system(MEMS)technique,which guaranteed high performance and robust reliability for repeatable usage.The sample operating fluidic microchannel was prepared by poly-(dimethylsiloxane) (PDMS)based soft lithography technique,which made it cheap enough for disposable applications.The PDMS microchannel chip was attached to the temperature controlling substrate for reconfigurable thermal applications.A thin PDMS film was used to seal the microchannel and bridge the functionalized substrate and the sample inside the channel,which facilitated heat transferring and prevented sample contaminating the temperature controlling substrate.Demonstrated by a one dimensional thermal resistance model,the thin PDMS film was important for the present reconfiguration applications.Thermal performance of this hybrid microsystem was examined,and the experimental results demonstrated that the chip system could work stably over hours with temperature variation less than 0.1oC.Multiple PDMS microchannel chips were tested on one heating substrate sequentially with a maximum intra-chip temperature difference of 1.0oC.DNA extracted from serum of a chronic hepatitis B virus(HBV)patient was amplified by this hybrid microsystem and the gel electrophoresis result indicated that the present reconfigurable microfluidic scheme worked successfully.
Sampling scheme optimization for diffuse optical tomography based on data and image space rankings
Sabir, Sohail; Kim, Changhwan; Cho, Sanghoon; Heo, Duchang; Kim, Kee Hyun; Ye, Jong Chul; Cho, Seungryong
2016-10-01
We present a methodology for the optimization of sampling schemes in diffuse optical tomography (DOT). The proposed method exploits singular value decomposition (SVD) of the sensitivity matrix, or weight matrix, in DOT. Two mathematical metrics are introduced to assess and determine the optimum source-detector measurement configuration in terms of data correlation and image space resolution. The key idea of the work is to weight each data measurement, or rows in the sensitivity matrix, and similarly to weight each unknown image basis, or columns in the sensitivity matrix, according to their contribution to the rank of the sensitivity matrix, respectively. The proposed metrics offer a perspective on the data sampling and provide an efficient way of optimizing the sampling schemes in DOT. We evaluated various acquisition geometries often used in DOT by use of the proposed metrics. By iteratively selecting an optimal sparse set of data measurements, we showed that one can design a DOT scanning protocol that provides essentially the same image quality at a much reduced sampling.
Rosanowski, S M; Cogger, N; Rogers, C W; Benschop, J; Stevenson, M A
2012-12-01
We conducted a cross-sectional survey to determine the demographic characteristics of non-commercial horses in New Zealand. A sampling frame of properties with non-commercial horses was derived from the national farms database, AgriBase™. Horse properties were stratified by property size and a generalised random-tessellated stratified (GRTS) sampling strategy was used to select properties (n=2912) to take part in the survey. The GRTS sampling design allowed for the selection of properties that were spatially balanced relative to the distribution of horse properties throughout the country. The registered decision maker of the property, as identified in AgriBase™, was sent a questionnaire asking them to describe the demographic characteristics of horses on the property, including the number and reason for keeping horses, as well as information about other animals kept on the property and the proximity of boundary neighbours with horses. The response rate to the survey was 38% (1044/2912) and the response rate was not associated with property size or region. A total of 5322 horses were kept for recreation, competition, racing, breeding, stock work, or as pets. The reasons for keeping horses and the number and class of horses varied significantly between regions and by property size. Of the properties sampled, less than half kept horses that could have been registered with Equestrian Sports New Zealand or either of the racing codes. Of the respondents that reported knowing whether their neighbours had horses, 58.6% (455/776) of properties had at least one boundary neighbour that kept horses. The results of this study have important implications for New Zealand, which has an equine population that is naïve to many equine diseases considered endemic worldwide. The ability to identify, and apply accurate knowledge of the population at risk to infectious disease control strategies would lead to more effective strategies to control and prevent disease spread during an
Fault isolation filter for networked control system with event-triggered sampling scheme.
Li, Shanbin; Sauter, Dominique; Xu, Bugong
2011-01-01
In this paper, the sensor data is transmitted only when the absolute value of difference between the current sensor value and the previously transmitted one is greater than the given threshold value. Based on this send-on-delta scheme which is one of the event-triggered sampling strategies, a modified fault isolation filter for a discrete-time networked control system with multiple faults is then implemented by a particular form of the Kalman filter. The proposed fault isolation filter improves the resource utilization with graceful fault estimation performance degradation. An illustrative example is given to show the efficiency of the proposed method.
Fault Isolation Filter for Networked Control System with Event-Triggered Sampling Scheme
Bugong Xu
2011-01-01
Full Text Available In this paper, the sensor data is transmitted only when the absolute value of difference between the current sensor value and the previously transmitted one is greater than the given threshold value. Based on this send-on-delta scheme which is one of the event-triggered sampling strategies, a modified fault isolation filter for a discrete-time networked control system with multiple faults is then implemented by a particular form of the Kalman filter. The proposed fault isolation filter improves the resource utilization with graceful fault estimation performance degradation. An illustrative example is given to show the efficiency of the proposed method.
Duy, Pham K; Chang, Kyeol; Sriphong, Lawan; Chung, Hoeil
2015-03-17
An axially perpendicular offset (APO) scheme that is able to directly acquire reproducible Raman spectra of samples contained in an oval container under variation of container orientation has been demonstrated. This scheme utilized an axially perpendicular geometry between the laser illumination and the Raman photon detection, namely, irradiation through a sidewall of the container and gathering of the Raman photon just beneath the container. In the case of either backscattering or transmission measurements, Raman sampling volumes for an internal sample vary when the orientation of an oval container changes; therefore, the Raman intensities of acquired spectra are inconsistent. The generated Raman photons traverse the same bottom of the container in the APO scheme; the Raman sampling volumes can be relatively more consistent under the same situation. For evaluation, the backscattering, transmission, and APO schemes were simultaneously employed to measure alcohol gel samples contained in an oval polypropylene container at five different orientations and then the accuracies of the determination of the alcohol concentrations were compared. The APO scheme provided the most reproducible spectra, yielding the best accuracy when the axial offset distance was 10 mm. Monte Carlo simulations were performed to study the characteristics of photon propagation in the APO scheme and to explain the origin of the optimal offset distance that was observed. In addition, the utility of the APO scheme was further demonstrated by analyzing samples in a circular glass container.
Tiao, G.C.; Daming, Xu; Pedrick, J.H.; Xiaodong, Zhu (Univ. of Chicago, IL (USA)); Reinsel, G.C. (Univ. of Wisconsin, Madison (USA)); Miller, A.J.; DeLuisi, J.J. (National Oceanic and Atmospheric Administration, Boulder, CO (USA)); Mateer, C.L. (Atmospheric Environment Service, Ottawa, Ontario (Canada)); Wuebbles, D.J. (Lawrence Livermore National Lab., CA (USA))
1990-11-20
This paper is concerned with temporal data requirements for the assessment of trends and for estimating spatial correlations of atmospheric species. The authors examine statistically three basic issues: (1) the effect of autocorrelations in monthly observations and the effect of the length of data record on the precision of trend estimates, (2) the effect of autocorrelations in the daily data on the sampling frequency requirements with respect to the representativeness of monthly averages for trend estimation, and (3) the effect of temporal sampling schemes on estimating spatial correlations of atmospheric species in neighboring stations. The principal findings are (1) the precision of trend estimates depends critically on the magnitude of auto-correlations in the monthly observations, (2) this precision is insensitive to the temporal sampling rates of daily measurements under systematic sampling, and (3) the estimate of spatial correlation between two neighboring stations is insensitive to temporal sampling rate under systematic sampling, but is sensitive to the time lag between measurements taken at the two stations. These results are based on methodological considerations as well as on empirical analysis of total and profile ozone and rawinsonde temperature data from selected ground stations.
Lapeyrouse, L M; Morera, O; Heyman, J M C; Amaya, M A; Pingitore, N E; Balcazar, H
2012-04-01
Examination of border-specific characteristics such as trans-border mobility and transborder health service illuminates the heterogeneity of border Hispanics and may provide greater insight toward understanding differential health behaviors and status among these populations. In this study, we create a descriptive profile of the concept of trans-border mobility by exploring the relationship between mobility status and a series of demographic, economic and socio-cultural characteristics among mobile and non-mobile Hispanics living in the El Paso-Juarez border region. Using a two-stage stratified random sampling design, bilingual interviewers collected survey data from border residents (n = 1,002). Findings show that significant economic, cultural, and behavioral differences exist between mobile and non-mobile respondents. While non-mobile respondents were found to have higher social economic status than their mobile counterparts, mobility across the border was found to offer less acculturated and poorer Hispanics access to alternative sources of health care and other services.
A coupled well-balanced and random sampling scheme for computing bubble oscillations*
Jung Jonathan
2012-04-01
Full Text Available We propose a finite volume scheme to study the oscillations of a spherical bubble of gas in a liquid phase. Spherical symmetry implies a geometric source term in the Euler equations. Our scheme satisfies the well-balanced property. It is based on the VFRoe approach. In order to avoid spurious pressure oscillations, the well-balanced approach is coupled with an ALE (Arbitrary Lagrangian Eulerian technique at the interface and a random sampling remap. Nous proposons un schéma de volumes finis pour étudier les oscillations d’une bulle sphérique de gaz dans l’eau. La symétrie sphérique fait apparaitre un terme source géométrique dans les équations d’Euler. Notre schéma est basé sur une approche VFRoe et préserve les états stationnaires. Pour éviter les oscillations de pression, l’approche well-balanced est couplée avec une approche ALE (Arbitrary Lagrangian Eulerian, et une étape de projection basée sur un échantillonage aléatoire.
Design of multishell sampling schemes with uniform coverage in diffusion MRI.
Caruyer, Emmanuel; Lenglet, Christophe; Sapiro, Guillermo; Deriche, Rachid
2013-06-01
In diffusion MRI, a technique known as diffusion spectrum imaging reconstructs the propagator with a discrete Fourier transform, from a Cartesian sampling of the diffusion signal. Alternatively, it is possible to directly reconstruct the orientation distribution function in q-ball imaging, providing so-called high angular resolution diffusion imaging. In between these two techniques, acquisitions on several spheres in q-space offer an interesting trade-off between the angular resolution and the radial information gathered in diffusion MRI. A careful design is central in the success of multishell acquisition and reconstruction techniques. The design of acquisition in multishell is still an open and active field of research, however. In this work, we provide a general method to design multishell acquisition with uniform angular coverage. This method is based on a generalization of electrostatic repulsion to multishell. We evaluate the impact of our method using simulations, on the angular resolution in one and two bundles of fiber configurations. Compared to more commonly used radial sampling, we show that our method improves the angular resolution, as well as fiber crossing discrimination. We propose a novel method to design sampling schemes with optimal angular coverage and show the positive impact on angular resolution in diffusion MRI. Copyright © 2012 Wiley Periodicals, Inc.
Eide, Helene K; Šaltytė Benth, Jūratė; Sortland, Kjersti; Halvorsen, Kristin; Almendingen, Kari
2015-01-01
There is a lack of accurate prevalence data on undernutrition and the risk of undernutrition among the hospitalised elderly in Europe and Norway. We aimed at estimating the prevalence of nutritional risk by using stratified sampling along with adequate power calculations. A cross-sectional study was carried out in the period 2011 to 2013 at a university hospital in Norway. Second-year nursing students in acute care clinical studies in twenty hospital wards screened non-demented elderly patients for nutritional risk, by employing the Nutritional Risk Screening 2002 (NRS2002) form. In total, 508 patients (48·8 % women and 51·2 % men) with a mean age of 79·6 (sd 6·4) years were screened by the students. Mean BMI was 24·9 (sd 4·9) kg/m(2), and the patients had been hospitalised for on average 5·3 (sd 6·3) d. WHO's BMI cut-off values identified 6·5 % as underweight, 48·0 % of normal weight and 45·5 % as overweight. Patients nutritionally at risk had been in hospital longer and had lower average weight and BMI compared with those not at risk (all P nutritional risk was estimated to be 45·4 (95 % CI 41·7 %, 49·0) %, ranging between 20·0 and 65·0 % on different hospital wards. The present results show that the prevalence of nutritional risk among elderly patients without dementia is high, suggesting that a large proportion of the hospitalised elderly are in need of nutritional treatment.
163 years of refinement: the British Geological Survey sample registration scheme
Howe, M. P.
2011-12-01
The British Geological Survey manages the largest UK geoscience samples collection, including: - 15,000 onshore boreholes, including over 250 km of drillcore - Vibrocores, gravity cores and grab samples from over 32,000 UK marine sample stations. 640 boreholes - Over 3 million UK fossils, including a "type and stratigraphic" reference collection of 250,000 fossils, 30,000 of which are "type, figured or cited" - Comprehensive microfossil collection, including many borehole samples - 290km of drillcore and 4.5 million cuttings samples from over 8000 UK continental shelf hydrocarbon wells - Over one million mineralogical and petrological samples, including 200,00 thin sections The current registration scheme was introduced in 1848 and is similar to that used by Charles Darwin on the Beagle. Every Survey collector or geologist has been issue with a unique prefix code of one or more letters and these were handwritten on preprinted numbers, arranged in books of 1 - 5,000 and 5,001 to 10,000. Similar labels are now computer printed. Other prefix codes are used for corporate collections, such as borehole samples, thin sections, microfossils, macrofossil sections, museum reference fossils, display quality rock samples and fossil casts. Such numbers infer significant immediate information to the curator, without the need to consult detailed registers. The registration numbers have been recorded in a series of over 1,000 registers, complete with metadata including sample ID, locality, horizon, collector and date. Citations are added as appropriate. Parent-child relationships are noted when re-registering subsubsamples. For example, a borehole sample BDA1001 could have been subsampled for a petrological thin section and off-cut (E14159), a fossil thin section (PF365), micropalynological slides (MPA273), one of which included a new holotype (MPK111), and a figured macrofossil (GSE1314). All main corporate collection now have publically-available online databases, such as Palaeo
Singal, Ashok K., E-mail: asingal@prl.res.in [Astronomy and Astrophysics Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 (India)
2014-07-01
We examine the consistency of the unified scheme of Fanaroff-Riley type II radio galaxies and quasars with their observed number and size distributions in the 3CRR sample. We separate the low-excitation galaxies from the high-excitation ones, as the former might not harbor a quasar within and thus may not be partaking in the unified scheme models. In the updated 3CRR sample, at low redshifts (z < 0.5), the relative number and luminosity distributions of high-excitation galaxies and quasars roughly match the expectations from the orientation-based unified scheme model. However, a foreshortening in the observed sizes of quasars, which is a must in the orientation-based model, is not seen with respect to radio galaxies even when the low-excitation galaxies are excluded. This dashes the hope that the unified scheme might still work if one includes only the high-excitation galaxies.
Kayastha, Nagendra; Solomatine, Dimitri; Lal Shrestha, Durga; van Griensven, Ann
2013-04-01
In recent years, a lot of attention in the hydrologic literature is given to model parameter uncertainty analysis. The robustness estimation of uncertainty depends on the efficiency of sampling method used to generate the best fit responses (outputs) and on ease of use. This paper aims to investigate: (1) how sampling strategies effect the uncertainty estimations of hydrological models, (2) how to use this information in machine learning predictors of models uncertainty. Sampling of parameters may employ various algorithms. We compared seven different algorithms namely, Monte Carlo (MC) simulation, generalized likelihood uncertainty estimation (GLUE), Markov chain Monte Carlo (MCMC), shuffled complex evolution metropolis algorithm (SCEMUA), differential evolution adaptive metropolis (DREAM), partical swarm optimization (PSO) and adaptive cluster covering (ACCO) [1]. These methods were applied to estimate uncertainty of streamflow simulation using conceptual model HBV and Semi-distributed hydrological model SWAT. Nzoia catchment in West Kenya is considered as the case study. The results are compared and analysed based on the shape of the posterior distribution of parameters, uncertainty results on model outputs. The MLUE method [2] uses results of Monte Carlo sampling (or any other sampling shceme) to build a machine learning (regression) model U able to predict uncertainty (quantiles of pdf) of a hydrological model H outputs. Inputs to these models are specially identified representative variables (past events precipitation and flows). The trained machine learning models are then employed to predict the model output uncertainty which is specific for the new input data. The problem here is that different sampling algorithms result in different data sets used to train such a model U, which leads to several models (and there is no clear evidence which model is the best since there is no basis for comparison). A solution could be to form a committee of all models U and
Schwientek, Marc; Guillet, Gaelle; Kuch, Bertram; Rügner, Hermann; Grathwohl, Peter
2014-05-01
Xenobiotic contaminants such as pharmaceuticals or personal care products typically are continuously introduced into the receiving water bodies via wastewater treatment plant (WWTP) outfalls and, episodically, via combined sewer overflows in the case of precipitation events. Little is known about how these chemicals behave in the environment and how they affect ecosystems and human health. Examples of traditional persistent organic pollutants reveal, that they may still be present in the environment even decades after they have been released. In this study a sampling strategy was developed which gives valuable insights into the environmental behaviour of xenobiotic chemicals. The method is based on the Lagrangian sampling scheme by which a parcel of water is sampled repeatedly as it moves downstream while chemical, physical, and hydrologic processes altering the characteristics of the water mass can be investigated. The Steinlach is a tributary of the River Neckar in Southwest Germany with a catchment area of 140 km². It receives the effluents of a WWTP with 99,000 inhabitant equivalents 4 km upstream of its mouth. The varying flow rate of effluents induces temporal patterns of electrical conductivity in the river water which enable to track parcels of water along the subsequent urban river section. These parcels of water were sampled a) close to the outlet of the WWTP and b) 4 km downstream at the confluence with the Neckar. Sampling was repeated at a 15 min interval over a complete diurnal cycle and 2 h composite samples were prepared. A model-based analysis demonstrated, on the one hand, that substances behaved reactively to a varying extend along the studied river section. On the other hand, it revealed that the observed degradation rates are likely dependent on the time of day. Some chemicals were degraded mainly during daytime (e.g. the disinfectant Triclosan or the phosphorous flame retardant TDCP), others as well during nighttime (e.g. the musk fragrance
Mielke, Steven L; Truhlar, Donald G
2016-01-21
Using Feynman path integrals, a molecular partition function can be written as a double integral with the inner integral involving all closed paths centered at a given molecular configuration, and the outer integral involving all possible molecular configurations. In previous work employing Monte Carlo methods to evaluate such partition functions, we presented schemes for importance sampling and stratification in the molecular configurations that constitute the path centroids, but we relied on free-particle paths for sampling the path integrals. At low temperatures, the path sampling is expensive because the paths can travel far from the centroid configuration. We now present a scheme for importance sampling of whole Feynman paths based on harmonic information from an instantaneous normal mode calculation at the centroid configuration, which we refer to as harmonically guided whole-path importance sampling (WPIS). We obtain paths conforming to our chosen importance function by rejection sampling from a distribution of free-particle paths. Sample calculations on CH4 demonstrate that at a temperature of 200 K, about 99.9% of the free-particle paths can be rejected without integration, and at 300 K, about 98% can be rejected. We also show that it is typically possible to reduce the overhead associated with the WPIS scheme by sampling the paths using a significantly lower-order path discretization than that which is needed to converge the partition function.
Rached, Nadhir B.
2015-11-13
The outage capacity (OC) is among the most important performance metrics of communication systems operating over fading channels. Of interest in the present paper is the evaluation of the OC at the output of the Equal Gain Combining (EGC) and the Maximum Ratio Combining (MRC) receivers. In this case, it can be seen that this problem turns out to be that of computing the Cumulative Distribution Function (CDF) for the sum of independent random variables. Since finding a closedform expression for the CDF of the sum distribution is out of reach for a wide class of commonly used distributions, methods based on Monte Carlo (MC) simulations take pride of price. In order to allow for the estimation of the operating range of small outage probabilities, it is of paramount importance to develop fast and efficient estimation methods as naive Monte Carlo (MC) simulations would require high computational complexity. In this line, we propose in this work two unified, yet efficient, hazard rate twisting Importance Sampling (IS) based approaches that efficiently estimate the OC of MRC or EGC diversity techniques over generalized independent fading channels. The first estimator is shown to possess the asymptotic optimality criterion and applies for arbitrary fading models, whereas the second one achieves the well-desired bounded relative error property for the majority of the well-known fading variates. Moreover, the second estimator is shown to achieve the asymptotic optimality property under the particular Log-normal environment. Some selected simulation results are finally provided in order to illustrate the substantial computational gain achieved by the proposed IS schemes over naive MC simulations.
伍长春; 张润楚
2006-01-01
In stratified survey sampling, sometimes we have complete auxiliary information. One of the fundamental questions is how to effectively use the complete auxiliary information at the estimation stage. In this paper, we extend the model-calibration method to obtain estimators of the finite population mean by using complete auxiliary information from stratified sampling survey data. We show that the resulting estimators effectively use auxiliary information at the estimation stage and possess a number of attractive features such as asymptotically design-unbiased irrespective of the working model and approximately model-unbiased under the model. When a linear working-model is used, the resulting estimators reduce to the usual calibration estimator(or GREG).
Geochemical sampling scheme optimization on mine wastes based on hyperspectral data
Zhao, T
2008-07-01
Full Text Available annealing uses the Weighted Means Shortest Distance (WMSD) criterion between sampling points. The scaled weight function intensively samples areas where an abundance of weathering mine waste occurs. A threshold is defined to constrain the sampling points...
An energy-efficient adaptive sampling scheme for wireless sensor networks
Masoum, Alireza; Meratnia, Nirvana; Havinga, Paul J.M.
2013-01-01
Wireless sensor networks are new monitoring platforms. To cope with their resource constraints, in terms of energy and bandwidth, spatial and temporal correlation in sensor data can be exploited to find an optimal sampling strategy to reduce number of sampling nodes and/or sampling frequencies while
40 CFR 761.316 - Interpreting PCB concentration measurements resulting from this sampling scheme.
2010-07-01
... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Interpreting PCB concentration... Â§ 761.79(b)(3) § 761.316 Interpreting PCB concentration measurements resulting from this sampling... concentration measured in that sample. If the sample surface concentration is not equal to or lower than the...
Stratified Medicine and Reimbursement Issues
Hans-Joerg eFugel
2012-10-01
Full Text Available Stratified Medicine (SM has the potential to target patient populations who will most benefit from a therapy while reducing unnecessary health interventions associated with side effects. The link between clinical biomarkers/diagnostics and therapies provides new opportunities for value creation to strengthen the value proposition to pricing and reimbursement (P&R authorities. However, the introduction of SM challenges current reimbursement schemes in many EU countries and the US as different P&R policies have been adopted for drugs and diagnostics. Also, there is a lack of a consistent process for value assessment of more complex diagnostics in these markets. New, innovative approaches and more flexible P&R systems are needed to reflect the added value of diagnostic tests and to stimulate investments in new technologies. Yet, the framework for access of diagnostic–based therapies still requires further development while setting the right incentives and appropriate align stakeholders interests when realizing long- term patient benefits. This article addresses the reimbursement challenges of SM approaches in several EU countries and the US outlining some options to overcome existing reimbursement barriers for stratified medicine.
Liu, Leo; Rather, Zakir Hussain; Chen, Zhe
2013-01-01
and adopts a methodology of importance sampling to maximize the information contained in the database so as to increase the accuracy of DT. Further, this paper also studies the effectiveness of DT by implementing its corresponding preventive control schemes. These approaches are tested on the detailed model......Decision Trees (DT) based security assessment helps Power System Operators (PSO) by providing them with the most significant system attributes and guiding them in implementing the corresponding emergency control actions to prevent system insecurity and blackouts. DT is obtained offline from time......-domain simulation and the process of data mining, which is then implemented online as guidelines for preventive control schemes. An algorithm named Classification and Regression Trees (CART) is used to train the DT and key to this approach lies on the accuracy of DT. This paper proposes contingency oriented DT...
How old is this bird? The age distribution under some phase sampling schemes.
Hautphenne, Sophie; Massaro, Melanie; Taylor, Peter
2017-04-03
In this paper, we use a finite-state continuous-time Markov chain with one absorbing state to model an individual's lifetime. Under this model, the time of death follows a phase-type distribution, and the transient states of the Markov chain are known as phases. We then attempt to provide an answer to the simple question "What is the conditional age distribution of the individual, given its current phase"? We show that the answer depends on how we interpret the question, and in particular, on the phase observation scheme under consideration. We then apply our results to the computation of the age pyramid for the endangered Chatham Island black robin Petroica traversi during the monitoring period 2007-2014.
ESTIMATION OF MEAN IN PRESENCE OF MISSING DATA UNDER TWO-PHASE SAMPLING SCHEME
Narendra Singh Thakur
2011-01-01
Full Text Available To estimate the population mean with imputation i.e. the technique of substitutingmissing data, there are a number of techniques available in literature like Ratio method ofimputation, Compromised method of imputation, Mean method of imputation, Ahmed method ofimputation, F-T method of imputation, and so on. If population mean of auxiliary information isunknown then these methods are not useful and the two-phase sampling is used to obtain thepopulation mean. This paper presents some imputation methods of for missing values in twophasesampling. Two different sampling designs in two-phase sampling are compared underimputed data. The bias and m.s.e of suggested estimators are derived in the form of populationparameters using the concept of large sample approximation. Numerical study is performed overtwo populations using the expressions of bias and m.s.e and efficiency compared with Ahmedestimators.
Shafiei, M.; Gharari, S.; Pande, S.; Bhulai, S.
2014-01-01
Posterior sampling methods are increasingly being used to describe parameter and model predictive uncertainty in hydrologic modelling. This paper proposes an alternative to random walk chains (such as DREAM-zs). We propose a sampler based on independence chains with an embedded feature of standardiz
Continuous quality control of the blood sampling procedure using a structured observation scheme
Seemann, Tine Lindberg; Nybo, Mads
2016-01-01
blood drawings by 39 phlebotomists were observed in the pilot study, while 84 blood drawings by 34 phlebotomists were observed in the follow-up study. In the pilot study, the three major error items were hand hygiene (42% error), mixing of samples (22%), and order of draw (21%). Minor significant...
Frequency-Selective Signal Sensing with Sub-Nyquist Uniform Sampling Scheme
Pierzchlewski, Jacek; Arildsen, Thomas
2015-01-01
by the Restricted Isometry Property, which is known from the field of compressed sensing. Then, compressed sensing is used to successfully reconstruct a wanted signal even if some of the uniform samples were randomly lost, e. g. due to ADC saturation. An experiment which tests the proposed method in practice...
da Costa, Nuno Maçarico; Hepp, Klaus; Martin, Kevan A C
2009-05-30
Synapses can only be morphologically identified by electron microscopy and this is often a very labor-intensive and time-consuming task. When quantitative estimates are required for pathways that contribute a small proportion of synapses to the neuropil, the problems of accurate sampling are particularly severe and the total time required may become prohibitive. Here we present a sampling method devised to count the percentage of rarely occurring synapses in the neuropil using a large sample (approximately 1000 sampling sites), with the strong constraint of doing it in reasonable time. The strategy, which uses the unbiased physical disector technique, resembles that used in particle physics to detect rare events. We validated our method in the primary visual cortex of the cat, where we used biotinylated dextran amine to label thalamic afferents and measured the density of their synapses using the physical disector method. Our results show that we could obtain accurate counts of the labeled synapses, even when they represented only 0.2% of all the synapses in the neuropil.
Yin, Jingjing; Samawi, Hani; Linder, Daniel
2016-07-01
A diagnostic cut-off point of a biomarker measurement is needed for classifying a random subject to be either diseased or healthy. However, the cut-off point is usually unknown and needs to be estimated by some optimization criteria. One important criterion is the Youden index, which has been widely adopted in practice. The Youden index, which is defined as the maximum of (sensitivity + specificity -1), directly measures the largest total diagnostic accuracy a biomarker can achieve. Therefore, it is desirable to estimate the optimal cut-off point associated with the Youden index. Sometimes, taking the actual measurements of a biomarker is very difficult and expensive, while ranking them without the actual measurement can be relatively easy. In such cases, ranked set sampling can give more precise estimation than simple random sampling, as ranked set samples are more likely to span the full range of the population. In this study, kernel density estimation is utilized to numerically solve for an estimate of the optimal cut-off point. The asymptotic distributions of the kernel estimators based on two sampling schemes are derived analytically and we prove that the estimators based on ranked set sampling are relatively more efficient than that of simple random sampling and both estimators are asymptotically unbiased. Furthermore, the asymptotic confidence intervals are derived. Intensive simulations are carried out to compare the proposed method using ranked set sampling with simple random sampling, with the proposed method outperforming simple random sampling in all cases. A real data set is analyzed for illustrating the proposed method.
Fuzzy logic scheme for tip-sample distance control for a low cost near field optical microscope
J.A. Márquez
2013-12-01
Full Text Available The control of the distance between the surface and the tip-sample of a Scanning Near Field Optical Microscope (SNOM is essential for a reliable surface mapping. The control algorithm should be able to maintain the system in a constant distance between the tip and the surface. In this system, nanometric adjustments should be made in order to sense topographies at the same scale with an appropriate resolution. These kinds of devices varies its properties through short periods of time, and it is required a control algorithm capable of handle these changes. In this work a fuzzy logic control scheme is proposed in order to manage the changes the device might have through the time, and to counter the effects of the non-linearity as well. Two inputs are used to program the rules inside the fuzzy logic controller, the difference between the reference signal and the sample signal (error, and the speed in which it decreases or increases. A lock-in amplifier is used as data acquisition hardware to sample the high frequency signals used to produce the tuning fork oscillations. Once these variables are read the control algorithm calculate a voltage output to move the piezoelectric device, approaching or removing the tip-probe from the sample analyzed.
Distribution of vaccine/antivirals and the 'least spread line' in a stratified population
Goldstein, E.; Apolloni, A.; Lewis, B.; Miller, J. C.; Macauley, M.; Eubank, S.; Lipsitch, M.; Wallinga, J.
2010-01-01
We describe a prioritization scheme for an allocation of a sizeable quantity of vaccine or antivirals in a stratified population. The scheme builds on an optimal strategy for reducing the epidemic's initial growth rate in a stratified mass-action model. The strategy is tested on the EpiSims network
da Jornada, Felipe H.; Qiu, Diana Y.; Louie, Steven G.
2017-01-01
First-principles calculations based on many-electron perturbation theory methods, such as the ab initio G W and G W plus Bethe-Salpeter equation (G W -BSE) approach, are reliable ways to predict quasiparticle and optical properties of materials, respectively. However, these methods involve more care in treating the electron-electron interaction and are considerably more computationally demanding when applied to systems with reduced dimensionality, since the electronic confinement leads to a slower convergence of sums over the Brillouin zone due to a much more complicated screening environment that manifests in the "head" and "neck" elements of the dielectric matrix. Here we present two schemes to sample the Brillouin zone for G W and G W -BSE calculations: the nonuniform neck subsampling method and the clustered sampling interpolation method, which can respectively be used for a family of single-particle problems, such as G W calculations, and for problems involving the scattering of two-particle states, such as when solving the BSE. We tested these methods on several few-layer semiconductors and graphene and show that they perform a much more efficient sampling of the Brillouin zone and yield two to three orders of magnitude reduction in the computer time. These two methods can be readily incorporated into several ab initio packages that compute electronic and optical properties through the G W and G W -BSE approaches.
Tchoubi, Sébastien; Sobngwi-Tambekou, Joëlle; Noubiap, Jean Jacques N.; Asangbeh, Serra Lem; Nkoum, Benjamin Alexandre; Sobngwi, Eugene
2015-01-01
Background Childhood obesity is one of the most serious public health challenges of the 21st century. The prevalence of overweight and obesity among children (obesity among children aged 6 months to 5 years in Cameroon in 2011. Methods Four thousand five hundred and eighteen children (2205 boys and 2313 girls) aged between 6 to 59 months were sampled in the 2011 Demographic Health Survey (DHS) database. Body Mass Index (BMI) z-scores based on WHO 2006 reference population was chosen to estimate overweight (BMI z-score > 2) and obesity (BMI for age > 3). Regression analyses were performed to investigate risk factors of overweight/obesity. Results The prevalence of overweight and obesity was 8% (1.7% for obesity alone). Boys were more affected by overweight than girls with a prevalence of 9.7% and 6.4% respectively. The highest prevalence of overweight was observed in the Grassfield area (including people living in West and North-West regions) (15.3%). Factors that were independently associated with overweight and obesity included: having overweight mother (adjusted odds ratio (aOR) = 1.51; 95% CI 1.15 to 1.97) and obese mother (aOR = 2.19; 95% CI = 155 to 3.07), compared to having normal weight mother; high birth weight (aOR = 1.69; 95% CI 1.24 to 2.28) compared to normal birth weight; male gender (aOR = 1.56; 95% CI 1.24 to 1.95); low birth rank (aOR = 1.35; 95% CI 1.06 to 1.72); being aged between 13–24 months (aOR = 1.81; 95% CI = 1.21 to 2.66) and 25–36 months (aOR = 2.79; 95% CI 1.93 to 4.13) compared to being aged 45 to 49 months; living in the grassfield area (aOR = 2.65; 95% CI = 1.87 to 3.79) compared to living in Forest area. Muslim appeared as a protective factor (aOR = 0.67; 95% CI 0.46 to 0.95).compared to Christian religion. Conclusion This study underlines a high prevalence of early childhood overweight with significant disparities between ecological areas of Cameroon. Risk factors of overweight included high maternal BMI, high birth weight, male
Fluttering in Stratified Flows
Lam, Try; Vincent, Lionel; Kanso, Eva
2016-11-01
The descent motion of heavy objects under the influence of gravitational and aerodynamic forces is relevant to many branches of engineering and science. Examples range from estimating the behavior of re-entry space vehicles to studying the settlement of marine larvae and its influence on underwater ecology. The behavior of regularly shaped objects freely falling in homogeneous fluids is relatively well understood. For example, the complex interaction of a rigid coin with the surrounding fluid will cause it to either fall steadily, flutter, tumble, or be chaotic. Less is known about the effect of density stratification on the descent behavior. Here, we experimentally investigate the descent of discs in both pure water and in a linearly salt-stratified fluids where the density is varied from 1.0 to 1.14 of that of water where the Brunt-Vaisala frequency is 1.7 rad/sec and the Froude number Fr robots for space exploration and underwater missions.
Zhang, Xian-Ming; Han, Qing-Long
2016-12-01
This paper is concerned with decentralized event-triggered dissipative control for systems with the entries of the system outputs having different physical properties. Depending on these different physical properties, the entries of the system outputs are grouped into multiple nodes. A number of sensors are used to sample the signals from different nodes. A decentralized event-triggering scheme is introduced to select those necessary sampled-data packets to be transmitted so that communication resources can be saved significantly while preserving the prescribed closed-loop performance. First, in order to organize the decentralized data packets transmitted from the sensor nodes, a data packet processor (DPP) is used to generate a new signal to be held by the zero-order-hold once the signal stored by the DPP is updated at some time instant. Second, under the mechanism of the DPP, the resulting closed-loop system is modeled as a linear system with an interval time-varying delay. A sufficient condition is derived such that the closed-loop system is asymptotically stable and strictly (Q0,S0,R0) -dissipative, where Q0,S0 , and R0 are real matrices of appropriate dimensions with Q0 and R0 symmetric. Third, suitable output-based controllers can be designed based on solutions to a set of a linear matrix inequality. Finally, two examples are given to demonstrate the effectiveness of the proposed method.
Stably stratified magnetized stars in general relativity
Yoshida, Shijun; Shibata, Masaru
2012-01-01
We construct magnetized stars composed of a fluid stably stratified by entropy gradients in the framework of general relativity, assuming ideal magnetohydrodynamics and employing a barotropic equation of state. We first revisit basic equations for describing stably-stratified stationary axisymmetric stars containing both poloidal and toroidal magnetic fields. As sample models, the magnetized stars considered by Ioka and Sasaki (2004), inside which the magnetic fields are confined, are modified to the ones stably stratified. The magnetized stars newly constructed in this study are believed to be more stable than the existing relativistic models because they have both poloidal and toroidal magnetic fields with comparable strength, and magnetic buoyancy instabilities near the surface of the star, which can be stabilized by the stratification, are suppressed.
Yan, Hongyong; Yang, Lei; Li, Xiang-Yang
2016-12-01
High-order staggered-grid finite-difference (SFD) schemes have been universally used to improve the accuracy of wave equation modeling. However, the high-order SFD coefficients on spatial derivatives are usually determined by the Taylor-series expansion (TE) method, which just leads to great accuracy at small wavenumbers for wave equation modeling. Some conventional optimization methods can achieve high accuracy at large wavenumbers, but they hardly guarantee the small numerical dispersion error at small wavenumbers. In this paper, we develop new optimal explicit SFD (ESFD) and implicit SFD (ISFD) schemes for wave equation modeling. We first derive the optimal ESFD and ISFD coefficients for the first-order spatial derivatives by applying the combination of the TE and the sampling approximation to the dispersion relation, and then analyze their numerical accuracy. Finally, we perform elastic wave modeling with the ESFD and ISFD schemes based on the TE method and the optimal method, respectively. When the appropriate number and interval for the sampling points are chosen, these optimal schemes have extremely high accuracy at small wavenumbers, and can also guarantee small numerical dispersion error at large wavenumbers. Numerical accuracy analyses and modeling results demonstrate the optimal ESFD and ISFD schemes can efficiently suppress the numerical dispersion and significantly improve the modeling accuracy compared to the TE-based ESFD and ISFD schemes.
Sundareshan, Malur K.; Zegers, Pablo
1999-07-01
Super-resolution algorithms are often needed to enhance the resolution of diffraction-limited imagery acquired from certain sensors, particularly those operating in the millimeter-wave range. While several powerful iterative procedures for image superresolution are currently being developed, some practical implementation considerations become important in order to reduce the computational complexity and improve the convergence rate in deploying these algorithms in applications where real-time performance is of critical importance. Issues of particular interest are representation of the acquired imagery data on appropriate sample grids and the availability of oversampled data prior to super-resolution processing. Sampling at the Nyquist rate corresponds to an optimal spacing of detector elements or a scan rate that provides the largest dwell time (for scan- type focal plane imaging arrays), thus ensuring an increased SNR in the acquired image. However, super-resolution processing of this data could produce aliasing of the spectral components, leading not only to inaccurate estimates of the frequencies beyond the sensor cutoff frequency but also corruption of the passband itself, in turn resulting in a restored image that is poorer than the original. Obtaining sampled image data at a rate higher than the Nyquist rate can be accomplished either during data collection by modifying the acquisition hardware or as a post-acquisition signal processing step. If the ultimate goal in obtaining the oversampled image is to perform super- resolution, however, upsampling operations implemented as part of the overall signal processing software can offer several important benefits compared to acquiring oversampled data by hardware methods (such as by increasing number of detector elements in the sensor array or by microscanning). In this paper, we shall give a mathematical characterization of the process of image representation on a sample grid and establish the role of
2015-01-01
The premarital sex of senior students in some universities of Anhui province is investigated. To protect the privacy of respondents, applying randomized response technique and stratified three-stage method, the proportion of senior students premari-tal sex is studied using attribute characteristic Warner model. According to total probability formulas and variance's basic properties in Probability and Mathematical Statistics and the classical sampling theory of Cochran, the proportion and variance of senior college students premarital sex are deduced at all levels and stages. The survey reveals that the proportion of senior students premarital sex is high. Therefore, we should actively instruct the undergraduates to treat the issues of premarital sex properly and rationally.%对安徽省某高校大四学生婚前性行为进行抽样调查,为保护被调查对象的隐私,采用随机应答技术( Random-ized Response Technique,简写为RRT)结合分层三阶段抽样调查方法,利用属性特征敏感问题Warner模型分析该校大四学生发生婚前性行为的比例。运用全概率公式及方差的基本性质等概率论与数理统计知识,结合Cochran W. G的经典抽样理论,推导出各层各阶段大四学生发生婚前性行为的比例及其方差。调查结果显示大四学生婚前性行为发生比例高。为此,应该积极引导大学生理性正确的对待婚前性行为。
Nakai, Yoshikatsu; Nin, Kazuko; Teramukai, Satoshi; Taniguchi, Ataru; Fukushima, Mitsuo; Wonderlich, Stephen A
2013-08-01
The purposes of this study were to compare DSM-IV diagnostic criteria and the Broad Categories for the Diagnosis of Eating Disorders (BCD-ED) scheme in terms of the number of cases of Eating Disorder Not Otherwise Specified (EDNOS) and to test which diagnostic tool better captures the variance of psychiatric symptoms in a Japanese sample. One thousand and twenty-nine women with an eating disorder (ED) participated in this study. Assessment methods included structured clinical interviews and administration of the Eating Attitudes Test and the Eating Disorder Inventory. The BCD-ED scheme dramatically decreased the proportion of DSM-IV EDNOS from 45.1% to 1.5%. However, the categorization of patients with the BCD-ED scheme was less able to capture the variance in psychopathology scales than the DSM-IV, suggesting that the BCD-ED scheme may differentiate ED groups less effectively than the DSM-IV. These results suggest that the BCD-ED scheme may have the potential to eliminate the use of DSM-IV EDNOS, but it may have problems capturing the variance of psychiatric symptoms.
Electromagnetic waves in stratified media
Wait, James R; Fock, V A; Wait, J R
2013-01-01
International Series of Monographs in Electromagnetic Waves, Volume 3: Electromagnetic Waves in Stratified Media provides information pertinent to the electromagnetic waves in media whose properties differ in one particular direction. This book discusses the important feature of the waves that enables communications at global distances. Organized into 13 chapters, this volume begins with an overview of the general analysis for the electromagnetic response of a plane stratified medium comprising of any number of parallel homogeneous layers. This text then explains the reflection of electromagne
Stratified medicine and reimbursement issues
Fugel, Hans-Joerg; Nuijten, Mark; Postma, Maarten
2012-01-01
Stratified Medicine (SM) has the potential to target patient populations who will most benefit from a therapy while reducing unnecessary health interventions associated with side effects. The link between clinical biomarkers/diagnostics and therapies provides new opportunities for value creation to
An Assessment of the Kwabre District Mutual Health Insurance Scheme in Ghana
D. Adei
2012-09-01
Full Text Available The National Health Insurance Scheme (NHIS in Ghana has been in operation since 2005 as a nationwide health financing option in the form of District Mutual Health Insurance Schemes. With the Kwabre District Mutual Health Insurance Scheme as a case study the study sought to assess; households level of satisfaction, challenges affecting the scheme, the scheme’s sustainability prospects and make recommendations to inform policy. Primary data were obtained through a household sample of 203, which was distributed through a proportionate stratified sampling technique. Interview guides were used to obtain information from 12 accredited health service providers and the scheme management. Secondary data were also acquired from the Kwabre East District Health Directorate (DHD and the scheme’s management office. Data analysis indicated that, the scheme is substantially dependent on tax funding (93.5%. Everybody pays for the scheme through taxation (NHIL but unfortunately the scheme excludes over 72.1% of the population it covers. There is a low internal fund generation as a factor of excessive disenrollment resulting from membership non-renewal. Based on this premise, the scheme may not be sustainable in the long run as a Mutual Health Insurance Scheme since the schemes are dependent on the collective pool of resources. It is recommended that Government should boldly implement the one-time premium on a progressive and reasonable premium affordable to all. Conscious efforts should thus be geared towards improving revenue collection from premiums through education, enforcement of subscription renewal and introduction of copayment.
Wang, Jianhua; Hansen, Elo Harald
2003-01-01
for on-line matrix separation and pre-concentration of trace levels of metals with detection by ICP-MS. It highlights some of the frequently applied on-line, sample-pre-treatment schemes, including solid phase extraction (SPE), on-wall molecular sorption and precipitate/(co)-precipitate retention using...... a polytetrafluoroethylene (PTFE) knotted reactor (KR), solvent extraction-back extraction and hydride/vapor generation. It also addresses a novel, robust approach, whereby the protocol of SI-LOV-bead injection (BI) on-line separation and pre-concentration of ultra-trace levels of metals by a renewable microcolumn...
2006-03-01
3.22 shows an equivalent plot for the secondary case (100 MHz sampled at 1 GHz) in which only widths above 8-bits can be used for phase imbalance...phase imbalance, but only above 7-bits for amplitude imbalance. For the secondary case in Figure 3.24, the use of bit-widths above 8-bits for phase
Wang, Jianhua; Hansen, Elo Harald
2005-01-01
Flow injection (FI) analysis, the first generation of this technique, became in the 1990s supplemented by its second generation, sequential injection (SI), and most recently by the third generation (i.e.,Lab-on-Valve). The dominant role played by FI in automatic, on-line, sample pretreatments...
Straver, R.; Sistermans, E.A.; Holstege, H.; Visser, A.; Oudejans, C.B.M.; Reinders, M.J.T.
2013-01-01
Genetic disorders can be detected by prenatal diagnosis using Chorionic Villus Sampling, but the 1:100 chance to result in miscarriage restricts the use to fetuses that are suspected to have an aberration. Detection of trisomy 21 cases noninvasively is now possible owing to the upswing of next-gener
Msangi Shandala
2009-04-01
Full Text Available Abstract Background Malaria vector sampling is the best method for understanding the vector dynamics and infectivity; thus, disease transmission seasonality can be established. There is a need to protecting humans involved in the sampling of disease vectors during surveillance or in control programmes. In this study, human landing catch, two cow odour baited resting boxes and an unbaited resting box were evaluated as vector sampling tools in an area with a high proportion of Anopheles arabiensis, as the major malaria vector. Methods Three resting boxes were evaluated against human landing catch. Two were baited with cow odour, while the third was unbaited. The inner parts of the boxes were covered with black cloth materials. Experiments were arranged in latin-square design. Boxes were set in the evening and left undisturbed; mosquitoes were collected at 06:00 am the next morning, while human landing catch was done overnight. Results A total of 9,558 An. arabiensis mosquitoes were collected. 17.5% (N = 1668 were collected in resting box baited with cow body odour, 42.5% (N = 4060 in resting box baited with cow urine, 15.1% (N = 1444 in unbaited resting box and 24.9% (N = 2386 were collected by human landing catch technique. In analysis, the house positions had no effect on the density of mosquitoes caught (DF = 3, F = 0.753, P = 0.387; the sampling technique had significant impact on the caught mosquitoes densities (DF = 3, F 37. 944, P Conclusion Odour-baited resting boxes have shown the possibility of replacing the existing traditional method (human landing catch for sampling malaria vectors in areas with a high proportion of An. arabiensis as malaria vectors. Further evaluations of fermented urine and longevity of the urine odour still need to be investigated.
Information content of household-stratified epidemics
T.M. Kinyanjui
2016-09-01
Full Text Available Household structure is a key driver of many infectious diseases, as well as a natural target for interventions such as vaccination programs. Many theoretical and conceptual advances on household-stratified epidemic models are relatively recent, but have successfully managed to increase the applicability of such models to practical problems. To be of maximum realism and hence benefit, they require parameterisation from epidemiological data, and while household-stratified final size data has been the traditional source, increasingly time-series infection data from households are becoming available. This paper is concerned with the design of studies aimed at collecting time-series epidemic data in order to maximize the amount of information available to calibrate household models. A design decision involves a trade-off between the number of households to enrol and the sampling frequency. Two commonly used epidemiological study designs are considered: cross-sectional, where different households are sampled at every time point, and cohort, where the same households are followed over the course of the study period. The search for an optimal design uses Bayesian computationally intensive methods to explore the joint parameter-design space combined with the Shannon entropy of the posteriors to estimate the amount of information in each design. For the cross-sectional design, the amount of information increases with the sampling intensity, i.e., the designs with the highest number of time points have the most information. On the other hand, the cohort design often exhibits a trade-off between the number of households sampled and the intensity of follow-up. Our results broadly support the choices made in existing epidemiological data collection studies. Prospective problem-specific use of our computational methods can bring significant benefits in guiding future study designs.
Effects of unstratified and centre-stratified randomization in multi-centre clinical trials.
Anisimov, Vladimir V
2011-01-01
This paper deals with the analysis of randomization effects in multi-centre clinical trials. The two randomization schemes most often used in clinical trials are considered: unstratified and centre-stratified block-permuted randomization. The prediction of the number of patients randomized to different treatment arms in different regions during the recruitment period accounting for the stochastic nature of the recruitment and effects of multiple centres is investigated. A new analytic approach using a Poisson-gamma patient recruitment model (patients arrive at different centres according to Poisson processes with rates sampled from a gamma distributed population) and its further extensions is proposed. Closed-form expressions for corresponding distributions of the predicted number of the patients randomized in different regions are derived. In the case of two treatments, the properties of the total imbalance in the number of patients on treatment arms caused by using centre-stratified randomization are investigated and for a large number of centres a normal approximation of imbalance is proved. The impact of imbalance on the power of the study is considered. It is shown that the loss of statistical power is practically negligible and can be compensated by a minor increase in sample size. The influence of patient dropout is also investigated. The impact of randomization on predicted drug supply overage is discussed.
Suppression of stratified explosive interactions
Meeks, M.K.; Shamoun, B.I.; Bonazza, R.; Corradini, M.L. [Wisconsin Univ., Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics
1998-01-01
Stratified Fuel-Coolant Interaction (FCI) experiments with Refrigerant-134a and water were performed in a large-scale system. Air was uniformly injected into the coolant pool to establish a pre-existing void which could suppress the explosion. Two competing effects due to the variation of the air flow rate seem to influence the intensity of the explosion in this geometrical configuration. At low flow rates, although the injected air increases the void fraction, the concurrent agitation and mixing increases the intensity of the interaction. At higher flow rates, the increase in void fraction tends to attenuate the propagated pressure wave generated by the explosion. Experimental results show a complete suppression of the vapor explosion at high rates of air injection, corresponding to an average void fraction of larger than 30%. (author)
Silvestre, A M; Petim-Batista, F; Colaço, J
2006-05-01
Daily milk yield over the course of the lactation follows a curvilinear pattern, so a suitable function is required to model this curve. In this study, 7 functions (Wood, Wilmink, Ali and Schaeffer, cubic splines, and 3 Legendre polynomials) were used to model the lactation curve at the phenotypic level, using both daily observations and data from commonly used recording schemes. The number of observations per lactation varied from 4 to 11. Several criteria based on the analysis of the real error were used to compare models. The performance of models showed few discrepancies in the comparison criteria when daily or 4-weekly (with first test at days in milk 8) data by lactation were used. The performance of the Wood, Wilmink, and Ali and Schaeffer models were highly affected by the reduction of the sample dimension. The results of this work support the idea that the performance of these models depends on the sample properties but also shows considerable variation within the sampling groups.
A New Deferred Sentencing Scheme
N. K. Chakravarti
1968-10-01
Full Text Available A new deferred sentencing scheme resembling double sampling scheme has been suggested from viewpoint of operational and administrative. It is recommended particularly when the inspection is destructive. The O.C. curves of the scheme for two sample sizes of 5 and 10 have been given.
Stratified wake of an accelerating hydrofoil
Ben-Gida, Hadar; Gurka, Roi
2015-01-01
Wakes of towed and self-propelled bodies in stratified fluids are significantly different from non-stratified wakes. Long time effects of stratification on the development of the wakes of bluff bodies moving at constant speed are well known. In this experimental study we demonstrate how buoyancy affects the initial growth of vortices developing in the wake of a hydrofoil accelerating from rest. Particle image velocimetry measurements were applied to characterize the wake evolution behind a NACA 0015 hydrofoil accelerating in water and for low Reynolds number and relatively strong and stably stratified fluid (Re=5,000, Fr~O(1)). The analysis of velocity and vorticity fields, following vortex identification and an estimate of the circulation, reveal that the vortices in the stratified fluid case are stretched along the streamwise direction in the near wake. The momentum thickness profiles show lower momentum thickness values for the stratified late wake compared to the non-stratified wake, implying that the dra...
How stratified is mantle convection?
Puster, Peter; Jordan, Thomas H.
1997-04-01
We quantify the flow stratification in the Earth's mid-mantle (600-1500 km) in terms of a stratification index for the vertical mass flux, Sƒ (z) = 1 - ƒ(z) / ƒref (z), in which the reference value ƒref(z) approximates the local flux at depth z expected for unstratified convection (Sƒ=0). Although this flux stratification index cannot be directly constrained by observations, we show from a series of two-dimensional convection simulations that its value can be related to a thermal stratification index ST(Z) defined in terms of the radial correlation length of the temperature-perturbation field δT(z, Ω). ST is a good proxy for Sƒ at low stratifications (SƒUniformitarian Principle. The bound obtained here from global tomography is consistent with local seismological evidence for slab flux into the lower mantle; however, the total material flux has to be significantly greater (by a factor of 2-3) than that due to slabs alone. A stratification index, Sƒ≲0.2, is sufficient to exclude many stratified convection models still under active consideration, including most forms of chemical layering between the upper and lower mantle, as well as the more extreme versions of avalanching convection governed by a strong endothermic phase change.
Core science: Stratified by a sunken impactor
Nakajima, Miki
2016-10-01
There is potential evidence for a stratified layer at the top of the Earth's core, but its origin is not well understood. Laboratory experiments suggest that the stratified layer could be a sunken remnant of the giant impact that formed the Moon.
A Fixpoint Semantics for Stratified Databases
沈一栋
1993-01-01
Przmusinski extended the notion of stratified logic programs,developed by Apt,Blair and Walker,and by van Gelder,to stratified databases that allow both negative premises and disjunctive consequents.However,he did not provide a fixpoint theory for such class of databases.On the other hand,although a fixpoint semantics has been developed by Minker and Rajasekar for non-Horn logic programs,it is tantamount to traditional minimal model semantics which is not sufficient to capture the intended meaning of negation in the premises of clauses in stratified databases.In this paper,a fixpoint approach to stratified databases is developed,which corresponds with the perfect model semantics.Moreover,algorithms are proposed for computing the set of perfect models of a stratified database.
Thompson, Steven K
2012-01-01
Praise for the Second Edition "This book has never had a competitor. It is the only book that takes a broad approach to sampling . . . any good personal statistics library should include a copy of this book." —Technometrics "Well-written . . . an excellent book on an important subject. Highly recommended." —Choice "An ideal reference for scientific researchers and other professionals who use sampling." —Zentralblatt Math Features new developments in the field combined with all aspects of obtaining, interpreting, and using sample data Sampling provides an up-to-date treat
van Leeuwen, Theo
2013-01-01
This chapter presents a framework for analysing colour schemes based on a parametric approach that includes not only hue, value and saturation, but also purity, transparency, luminosity, luminescence, lustre, modulation and differentiation....
GROUP VELOCITY CONTROL SCHEME WITH LOW DISSIPATION
无
2000-01-01
In order to prevent smearing the discontinuity, a modified term is added to the third order Upwind Compact Difference scheme to lower the dissipation error. Moreover, the dispersion error is controled to hold back the non-physical oscillation by means of the group velocity control. The scheme is used to simulate the interactions of shock-density stratified interface and the disturbed interface developing to vortex rollers. Numerical results are satisfactory.
Pötz, Katharina Anna; Haas, Rainer; Balzarova, Michaela
2013-01-01
Purpose – The rise of CSR followed a demand for CSR standards and guidelines. In a sector already characterized by a large number of standards, the authors seek to ask what CSR schemes apply to agribusiness, and how they can be systematically compared and analysed. Design....../methodology/approach – Following a deductive-inductive approach the authors develop a model to compare and analyse CSR schemes based on existing studies and on coding qualitative data on 216 CSR schemes. Findings – The authors confirm that CSR standards and guidelines have entered agribusiness and identify a complex landscape...... of schemes that can be categorized on focus areas, scales, mechanisms, origins, types and commitment levels. Research limitations/implications – The findings contribute to conceptual and empirical research on existing models to compare and analyse CSR standards. Sampling technique and depth of analysis limit...
LTRMP Fisheries Data - Stratified Random and Fixed Site Sampling
U.S. Geological Survey, Department of the Interior — The Long Term Resource Monitoring Programs (LTRMP) annual fish monitoring began on the Upper Mississippi and Illinois Rivers in 1989. During the first two years...
Prototypic Features of Loneliness in a Stratified Sample of Adolescents
Lasgaard, Mathias; Elklit, Ask
2009-01-01
Dominant theoretical approaches in loneliness research emphasize the value of personality characteristics in explaining loneliness. The present study examines whether dysfunctional social strategies and attributions in lonely adolescents can be explained by personality characteristics. A question......Dominant theoretical approaches in loneliness research emphasize the value of personality characteristics in explaining loneliness. The present study examines whether dysfunctional social strategies and attributions in lonely adolescents can be explained by personality characteristics...... loneliness independent of personality characteristics, demographics and social desirability. The study indicates that dysfunctional strategies and attributions in affiliative situations are directly related to loneliness in adolescence. These strategies and attributions may preclude lonely adolescents from...... guidance and intervention. Thus, professionals need to be knowledgeable about prototypic features of loneliness in addition to employing a pro-active approach when assisting adolescents who display prototypic features....
Direct simulation of the stably stratified turbulent Ekman layer
Coleman, G. N.; Ferziger, J. H.; Spalart, P. R.
1992-01-01
The Navier-Stokes equations and the Boussinesq approximation were used to compute a 3D time-dependent turbulent flow in the stably stratified Ekman layer over a smooth surface. The simulation data are found to be in very good agreement with atmospheric measurements when nondimensionalized according to Nieuwstadt's local scaling scheme. Results suggest that, when Reynolds number effects are taken into account, the 'constant Froud number' stable layer model (Brost and Wyngaard, 1978) and the 'shearing length' stable layer model (Hunt, 1985) for the dissipitation rate of turbulent kinetic energy are both valid. It is concluded that there is good agreement between the direct numerical simulation results and large-eddy simulation results obtained by Mason and Derbyshire (1990).
Thermals in stratified regions of the ISM
Rodriguez-Gonzalez, Ary
2013-01-01
We present a model of a "thermal" (i.e., a hot bubble) rising within an exponentially stratified region of the ISM. This model includes terms representing the ram pressure braking and the entrainment of environmental gas into the thermal. We then calibrate the free parameters associated with these two terms through a comparison with 3D numerical simulations of a rising bubble. Finally, we apply our "thermal" model to the case of a hot bubble produced by a SN within the stratified ISM of the Galactic disk.
On Stratified Vortex Motions under Gravity.
2014-09-26
AD-A156 930 ON STRATIFIED VORTEX MOTIONS UNDER GRAVITY (U) NAVAL i/i RESEARCH LAB WASHINGTON DC Y T FUNG 20 JUN 85 NRL-MIR-5564 UNCLASSIFIED F/G 20/4...Under Gravity LCn * Y. T. Fung Fluid Dynamics Branch - Marine Technologyv Division June 20, 1985 SO Cyk. NAVAL RESEARCH LABORATORY Washington, D.C...DN880-019 TITLE (Include Security Classification) On Stratified Vortex Motions Under Gravity 12 PERSONAL AUTHOR(S) Funa, Y.T. 13a. TYPE OF REPORT 13b
Mixing by microorganisms in stratified fluids
Wagner, Gregory L; Lauga, Eric
2014-01-01
We examine the vertical mixing induced by the swimming of microorganisms at low Reynolds and P\\'eclet numbers in a stably stratified ocean, and show that the global contribution of oceanic microswimmers to vertical mixing is negligible. We propose two approaches to estimating the mixing efficiency, $\\eta$, or the ratio of the rate of potential energy creation to the total rate-of-working on the ocean by microswimmers. The first is based on scaling arguments and estimates $\\eta$ in terms of the ratio between the typical organism size, $a$, and an intrinsic length scale for the stratified flow, $\\ell = \\left ( \
THERMALS IN STRATIFIED REGIONS OF THE ISM
A. Rodríguez-González
2013-01-01
Full Text Available We present a model of a “thermal” (i.e., a hot bubble rising within an exponentially stratified region of the ISM. This model includes terms representing the ram pressure braking and the entrainment of environmental gas into the thermal. We then calibrate the free parameters associated with these two terms through a comparison with 3D numerical simulations of a rising bubble. Finally, we apply our “thermal” model to the case of a hot bubble produced by a SN within the stratified ISM of the Galactic disk.
Stratified flows with variable density: mathematical modelling and numerical challenges.
Murillo, Javier; Navas-Montilla, Adrian
2017-04-01
Stratified flows appear in a wide variety of fundamental problems in hydrological and geophysical sciences. They may involve from hyperconcentrated floods carrying sediment causing collapse, landslides and debris flows, to suspended material in turbidity currents where turbulence is a key process. Also, in stratified flows variable horizontal density is present. Depending on the case, density varies according to the volumetric concentration of different components or species that can represent transported or suspended materials or soluble substances. Multilayer approaches based on the shallow water equations provide suitable models but are not free from difficulties when moving to the numerical resolution of the governing equations. Considering the variety of temporal and spatial scales, transfer of mass and energy among layers may strongly differ from one case to another. As a consequence, in order to provide accurate solutions, very high order methods of proved quality are demanded. Under these complex scenarios it is necessary to observe that the numerical solution provides the expected order of accuracy but also converges to the physically based solution, which is not an easy task. To this purpose, this work will focus in the use of Energy balanced augmented solvers, in particular, the Augmented Roe Flux ADER scheme. References: J. Murillo , P. García-Navarro, Wave Riemann description of friction terms in unsteady shallow flows: Application to water and mud/debris floods. J. Comput. Phys. 231 (2012) 1963-2001. J. Murillo B. Latorre, P. García-Navarro. A Riemann solver for unsteady computation of 2D shallow flows with variable density. J. Comput. Phys.231 (2012) 4775-4807. A. Navas-Montilla, J. Murillo, Energy balanced numerical schemes with very high order. The Augmented Roe Flux ADER scheme. Application to the shallow water equations, J. Comput. Phys. 290 (2015) 188-218. A. Navas-Montilla, J. Murillo, Asymptotically and exactly energy balanced augmented flux
Turbulent Mixing in Stably Stratified Flows
2008-03-01
Liege Colloquium on Ocean Hydrodynamics, volume 46, page 19889898. Elsevier, 1987. R. M. Kerr. Higher-order derivative correlations and the alignment of...19th International Liege Colloquium on Ocean Hydrodynamics, volume 46, pages 3-9. Elsevier, 1988. P. Meunier and G. Spedding. Stratified propelled
Nitrogen transformations in stratified aquatic microbial ecosystems
Revsbech, Niels Peter; Risgaard-Petersen, N.; Schramm, Andreas
2006-01-01
Abstract New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about n...
A NONHYDROSTATIC NUMERICAL MODEL FOR DENSITY STRATIFIED FLOW AND ITS APPLICATIONS
无
2008-01-01
A modular numerical model was developed for simulating density-stratified flow in domains with irregular bottom topography. The model was designed for examining interactions between stratified flow and topography, e.g., tidally driven flow over two-dimensional sills or internal solitary waves propagating over a shoaling bed. The model was based on the non-hydrostatic vorticity-stream function equations for a continuously stratified fluid in a rotating frame. A self-adaptive grid was adopted in the vertical coordinate, the Alternative Direction Implicit (ADI) scheme was used for the time marching equations while the Poisson equation for stream-function was solved based on the Successive Over Relaxation (SOR) iteration with the Chebyshev acceleration. The numerical techniques were described and three applications of the model were presented.
胡怀中; 孙连明; 刘文江
2005-01-01
A new identification method for a linear discrete-time closed-loop system is proposed based on an output over-sampling scheme. When the system outputs are over-sampled the new output sequences would contain more information about the plant structure. Using general least squares method (GLS) the plant over-sampled model should be recognized. Then the original plant model should be obtained by its relationship with the over-sampled model. Compared with conventional approaches the advantage of the new method is that even if the ordinary identifiability conditions are not satisfied, a close-loop system can be identified by using the oversampled output without utilizing any external test signal. Accuracy analysis shows the relationship between the estimation error and the over-sampling rate. Numerical simulation illustrates its effectiveness.
Chomchoei, Roongrat; Miró, Manuel; Hansen, Elo Harald
2005-01-01
An automated sequential injection (SI) system incorporating a dual-conical microcolumn is proposed as a versatile approach for the accommodation of both single and sequential extraction schemes for metal fractionation of solid samples of environmental concern. Coupled to flame atomic absorption...... spectrometric detection and used for the determination of Cu as a model analyte, the potentials of this novel hyphenated approach are demonstrated by the ability of handling up to 300 mg sample of a nonhomogeneous sewage amended soil (viz., CRM 483). The three steps of the endorsed Standards, Measurements...
Methane metabolism in a stratified boreal lake
Nykänen, Hannu; Peura, Sari; Kankaala, Paula; Jones, Roger
2013-04-01
Stratified lakes, typical of the boreal zone, are naturally anoxic from their bottoms. In these lakes methanogenesis can account for up to half of organic matter degradation. However, a major part of the methane (CH4) is oxidized in the water column before reaching the atmosphere. Since methanotrophs use CH4 as their sole carbon and energy source, much CH4-derived carbon is incorporated into their biomass. Microbially produced CH4 has strongly negative δ13C compared to other carbon forms in ecosystems, making it possible to follow its route in food webs. However, only a few studies have estimated the amount of this microbial biomass or its carbon stable isotopic composition due to difficulties in separating it from other biomass or from other carbon forms in the water column. We estimated methanotrophic biomass from measured CH4 oxidation, and δ13C of the biomass from measured δ13C values of CH4, DIC, POM and DOC. An estimate of the fraction of methanotrophs in total microbial biomass is derived from bacterial community composition measurements. The study was made in, Alinen Mustajärvi, a small (area 0.75 ha, maximum depth 6.5 m, mean depth 4.2 m,), oligotrophic, mesohumic headwater lake located in boreal coniferous forest in southern Finland. CH4 and DIC concentrations and their δ13C were measured over the deepest point of the lake at 1 m intervals. 13C of DOM and POM were analyzed from composite samples from epi-, meta-, and hypolimnion. Evasion of CH4 and carbon dioxide from the lake surface to the atmosphere was estimated with boundary layer diffusion equations. CH4oxidation was estimated by comparing differences between observed concentrations and CH4potentially transported by turbulent diffusion between different vertical layers in the lake and also by actual methanotrophy measurements and from vertical differences in δ13C-CH4. The estimate of CH4 production was based on the sum of oxidized and released CH4. Molecular microbiology methods were used to
Numerical simulation of stratified shear flow using a higher order Taylor series expansion method
Iwashige, Kengo; Ikeda, Takashi [Hitachi, Ltd. (Japan)
1995-09-01
A higher order Taylor series expansion method is applied to two-dimensional numerical simulation of stratified shear flow. In the present study, central difference scheme-like method is adopted for an even expansion order, and upwind difference scheme-like method is adopted for an odd order, and the expansion order is variable. To evaluate the effects of expansion order upon the numerical results, a stratified shear flow test in a rectangular channel (Reynolds number = 1.7x10{sup 4}) is carried out, and the numerical velocity and temperature fields are compared with experimental results measured by laser Doppler velocimetry thermocouples. The results confirm that the higher and odd order methods can simulate mean velocity distributions, root-mean-square velocity fluctuations, Reynolds stress, temperature distributions, and root-mean-square temperature fluctuations.
An immersed interface method for two-dimensional modelling of stratified flow in pipes
Berthelsen, Petter Andreas
2004-01-01
This thesis deals with the construction of a numerical method for solving two-dimensional elliptic interface problems, such as fully developed stratified flow in pipes. Interface problems are characterized by its non-smooth and often discontinuous behaviour along a sharp boundary separating the fluids or other materials. Classical numerical schemes are not suitable for these problems due to the irregular geometry of the interface. Standard finite difference discretization across the interface...
薛会民; 欧阳晶晖
2011-01-01
It expounds the innovative design for overall scheme of the milling-grinding machineAc-cording to the processing requirements of high efficiency and high surface quality for billet test sample,the principle scheme of machine tool was proposed based on combined innovation, which achieves a composite process of milling and grindingJn addition the grinding adopts modern belt grinding.The motion scheme of the machine tool was designed through analyzing movement functionsAs for general structure of the machine tool fixed beam gantry frame structure is adopted based on structural variation.The result indicates that the overall scheme innovation realizes the uniqueness design of the machine tool,which has good performance and can well satisfy the processing requirements of billet steel sample.%阐述了铣磨床总体方案的创新设计,针对钢坯检测试样高效率、高表面质量的加工要求,采用组合创新的方法,提出了在同一机床上实现铣削、磨削复合加工的工艺原理方案,并且机床的磨削加工采用了现代砂带磨削.通过分析机床的各种运动功能,设计了机床的运动方案.对于机床的总体结构布局,采用结构变异的方法,确定其为定梁龙门式框架结构.结果表明,通过总体方案的创新,实现了机床的独特性设计,所设计机床性能优良,很好地满足了钢坯检测试样的加工要求.
Drainage in a model stratified porous medium
Datta, Sujit S; 10.1209/0295-5075/101/14002
2013-01-01
We show that when a non-wetting fluid drains a stratified porous medium at sufficiently small capillary numbers Ca, it flows only through the coarsest stratum of the medium; by contrast, above a threshold Ca, the non-wetting fluid is also forced laterally, into part of the adjacent, finer strata. The spatial extent of this partial invasion increases with Ca. We quantitatively understand this behavior by balancing the stratum-scale viscous pressure driving the flow with the capillary pressure required to invade individual pores. Because geological formations are frequently stratified, we anticipate that our results will be relevant to a number of important applications, including understanding oil migration, preventing groundwater contamination, and sub-surface CO$_{2}$ storage.
Stably Stratified Flow in a Shallow Valley
Mahrt, L.
2017-01-01
Stratified nocturnal flow above and within a small valley of approximately 12-m depth and a few hundred metres width is examined as a case study, based on a network of 20 sonic anemometers and a central 20-m tower with eight levels of sonic anemometers. Several regimes of stratified flow over gentle topography are conceptually defined for organizing the data analysis and comparing with the existing literature. In our case study, a marginal cold pool forms within the shallow valley in the early evening but yields to larger ambient wind speeds after a few hours, corresponding to stratified terrain-following flow where the flow outside the valley descends to the valley floor. The terrain-following flow lasts about 10 h and then undergoes transition to an intermittent marginal cold pool towards the end of the night when the larger-scale flow collapses. During this 10-h period, the stratified terrain-following flow is characterized by a three-layer structure, consisting of a thin surface boundary layer of a few metres depth on the valley floor, a deeper boundary layer corresponding to the larger-scale flow, and an intermediate transition layer with significant wind-directional shear and possible advection of lee turbulence that is generated even for the gentle topography of our study. The flow in the valley is often modulated by oscillations with a typical period of 10 min. Cold events with smaller turbulent intensity and duration of tens of minutes move through the observational domain throughout the terrain-following period. One of these events is examined in detail.
Zhang, Zulin; Troldborg, Mads; Yates, Kyari; Osprey, Mark; Kerr, Christine; Hallett, Paul D; Baggaley, Nikki; Rhind, Stewart M; Dawson, Julian J C; Hough, Rupert L
2016-11-01
In many agricultural catchments of Europe and North America, pesticides occur at generally low concentrations with significant temporal variation. This poses several challenges for both monitoring and understanding ecological risks/impacts of these chemicals. This study aimed to compare the performance of passive and spot sampling strategies given the constraints of typical regulatory monitoring. Nine pesticides were investigated in a river currently undergoing regulatory monitoring (River Ugie, Scotland). Within this regulatory framework, spot and passive sampling were undertaken to understand spatiotemporal occurrence, mass loads and ecological risks. All the target pesticides were detected in water by both sampling strategies. Chlorotoluron was observed to be the dominant pesticide by both spot (maximum: 111.8ng/l, mean: 9.35ng/l) and passive sampling (maximum: 39.24ng/l, mean: 4.76ng/l). The annual pesticide loads were estimated to be 2735g and 1837g based on the spot and passive sampling data, respectively. The spatiotemporal trend suggested that agricultural activities were the primary source of the compounds with variability in loads explained in large by timing of pesticide applications and rainfall. The risk assessment showed chlorotoluron and chlorpyrifos posed the highest ecological risks with 23% of the chlorotoluron spot samples and 36% of the chlorpyrifos passive samples resulting in a Risk Quotient greater than 0.1. This suggests that mitigation measures might need to be taken to reduce the input of pesticides into the river. The overall comparison of the two sampling strategies supported the hypothesis that passive sampling tends to integrate the contaminants over a period of exposure and allows quantification of contamination at low concentration. The results suggested that within a regulatory monitoring context passive sampling was more suitable for flux estimation and risk assessment of trace contaminants which cannot be diagnosed by spot
Multi Dimensional CTL and Stratified Datalog
Theodore Andronikos
2010-02-01
Full Text Available In this work we define Multi Dimensional CTL (MD-CTL in short by extending CTL which is thedominant temporal specification language in practice. The need for Multi Dimensional CTL is mainlydue to the advent of semi-structured data. The common path nature of CTL and XPath which provides asuitable model for semi-structured data, has caused the emergence of work on specifying a relation amongthem aiming at exploiting the nice properties of CTL. Although the advantages of such an approach havealready been noticed [36, 26, 5], no formal definition of MD-CTL has been given. The goal of this workis twofold; a we define MD-CTL and prove that the “nice” properties of CTL (linear model checking andbounded model property transfer also to MD-CTL, b we establish new results on stratified Datalog. Inparticular, we define a fragment of stratified Datalog called Multi Branching Temporal (MBT in shortprograms that has the same expressive power as MD-CTL. We prove that by devising a linear translationbetween MBT and MD-CTL. We actually give the exact translation rules for both directions. We furtherbuild on this relation to prove that query evaluation is linear and checking satisfiability, containment andequivalence are EXPTIME–complete for MBT programs. The class MBT is the largest fragment of stratifiedDatalog for which such results exist in the literature.
Thermal mixing in a stratified environment
Kraemer, Damian; Cotel, Aline
1999-11-01
Laboratory experiments of a thermal impinging on a stratified interface have been performed. The thermal was released from a cylindrical reservoir located at the bottom of a Lucite tank. The stratified interface was created by filling the tank with two different saline solutions. The density of the lower layer is greater than that of the upper layer and the thermal fluid, thereby creating a stable stratification. A pH indicator, phenolphthalein, is used to visualize and quantify the amount of mixing produced by the impingement of the thermal at the interface. The upper layer contains a mixture of water, salt and sodium hydroxide. The thermal fluid is composed of water, sulfuric acid and phenolphthalein. When the thermal entrains and mixes fluid from the upper layer, a chemical reaction takes place, and the resulting mixed fluid is now visible. The ratio of base to acid, called the equivalence ratio, was varied throughout the experiments, as well as the Richardson number. The Richardson number is the ratio of potential to kinetic energy, and is based on the thermal quantities at the interface. Results indicate that the amount of mixing produced is proportional to the Richardson number raised to the -3/2 power. Previous experiments (Zhang and Cotel 1999) revealed that the entrainment rate of a thermal in a stratified environment follows the same power law.
STRATIFIED MODEL FOR ESTIMATING FATIGUE CRACK GROWTH RATE OF METALLIC MATERIALS
YANG Yong-yu; LIU Xin-wei; YANG Fan
2005-01-01
The curve of relationship between fatigue crack growth rate and the stress strength factor amplitude represented an important fatigue property in designing of damage tolerance limits and predicting life of metallic component parts. In order to have a morereasonable use of testing data, samples from population were stratified suggested by the stratified random sample model (SRAM). The data in each stratum corresponded to the same experiment conditions. A suitable weight was assigned to each stratified sample according to the actual working states of the pressure vessel, so that the estimation of fatigue crack growth rate equation was more accurate for practice. An empirical study shows that the SRAM estimation by using fatigue crack growth rate data from different stoves is obviously better than the estimation from simple random sample model.
Hansen, Elo Harald; Wang, Jianhua
Despite their excellent analytical chemical capacities, Electrothermal Atomic Absorption Spectrometry (ETAAS) and Inductively Coupled Plasma Mass Spectrometry (ICPMS), nevertheless, often require suitable pretreatment of the sample material in order to obtain the necessary sensitivity and selecti...
Sabbe, Pieter-Jan [Department of Analytical Chemistry, Ghent University, Krijgslaan 281-S12, Ghent (Belgium); Dowsett, Mark G. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); De Keersmaecker, Michel [Department of Analytical Chemistry, Ghent University, Krijgslaan 281-S12, Ghent (Belgium); Hand, Matthew [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Thompson, Paul [XMaS – The UK CRG, ESRF – The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9 (France); Department of Physics, University of Liverpool, Liverpool L69 7ZX (United Kingdom); Adriaens, Annemie, E-mail: annemie.adriaens@ugent.be [Department of Analytical Chemistry, Ghent University, Krijgslaan 281-S12, Ghent (Belgium)
2015-03-30
Highlights: • Periodically arranged cuprite reference material samples are presented. • The produced reference material is used for characterization of new XEOL microscope. • A priori sample surface characterization was done by XPS, XAS, XEOL–XANES and XRD. • Results indicated a heterogeneous mixture of mainly Cu{sub 2}O with CuO at near surface. • The produced patina provides intense optical luminescence upon X-ray bombardment. - Abstract: The synthesis and characterization of a reference sample containing a distinct geometrical pattern of Cu{sub 2}O (cuprite) are described. The sample is to be used as an assessment sample to evaluate a newly developed X-ray-excited optical luminescence (XEOL) microscope, built for non-destructive chemical imaging of metal and other surfaces. The sample was produced by heating in a reducing flame and subsequent air exposure. It was characterized both qualitatively and quantitatively using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy in both fluorescence mode (XAS) and optical luminescence mode (XEOL–XAS) and X-ray diffraction (XRD). Results indicate the presence of a layered structure comprising a heterogeneous mixture of cuprite and tenorite (CuO) with mainly cuprite (91.4%) in the near-surface regions and larger amounts of tenorite in the top 1–3 nm. The cuprite produced via this protocol was found to provide intense optical luminescence upon X-ray bombardment, which is particularly useful during the evaluation of the microscope.
On the Exploitation of Sensitivity Derivatives for Improving Sampling Methods
Cao, Yanzhao; Hussaini, M. Yousuff; Zang, Thomas A.
2003-01-01
Many application codes, such as finite-element structural analyses and computational fluid dynamics codes, are capable of producing many sensitivity derivatives at a small fraction of the cost of the underlying analysis. This paper describes a simple variance reduction method that exploits such inexpensive sensitivity derivatives to increase the accuracy of sampling methods. Three examples, including a finite-element structural analysis of an aircraft wing, are provided that illustrate an order of magnitude improvement in accuracy for both Monte Carlo and stratified sampling schemes.
The fully nonlinear stratified geostrophic adjustment problem
Coutino, Aaron; Stastna, Marek
2017-01-01
The study of the adjustment to equilibrium by a stratified fluid in a rotating reference frame is a classical problem in geophysical fluid dynamics. We consider the fully nonlinear, stratified adjustment problem from a numerical point of view. We present results of smoothed dam break simulations based on experiments in the published literature, with a focus on both the wave trains that propagate away from the nascent geostrophic state and the geostrophic state itself. We demonstrate that for Rossby numbers in excess of roughly 2 the wave train cannot be interpreted in terms of linear theory. This wave train consists of a leading solitary-like packet and a trailing tail of dispersive waves. However, it is found that the leading wave packet never completely separates from the trailing tail. Somewhat surprisingly, the inertial oscillations associated with the geostrophic state exhibit evidence of nonlinearity even when the Rossby number falls below 1. We vary the width of the initial disturbance and the rotation rate so as to keep the Rossby number fixed, and find that while the qualitative response remains consistent, the Froude number varies, and these variations are manifested in the form of the emanating wave train. For wider initial disturbances we find clear evidence of a wave train that initially propagates toward the near wall, reflects, and propagates away from the geostrophic state behind the leading wave train. We compare kinetic energy inside and outside of the geostrophic state, finding that for long times a Rossby number of around one-quarter yields an equal split between the two, with lower (higher) Rossby numbers yielding more energy in the geostrophic state (wave train). Finally we compare the energetics of the geostrophic state as the Rossby number varies, finding long-lived inertial oscillations in the majority of the cases and a general agreement with the past literature that employed either hydrostatic, shallow-water equation-based theory or
Inverse scattering of dispersive stratified structures
Skaar, Johannes
2012-01-01
We consider the inverse scattering problem of retrieving the structural parameters of a stratified medium consisting of dispersive materials, given knowledge of the complex reflection coefficient in a finite frequency range. It is shown that the inverse scattering problem does not have a unique solution in general. When the dispersion is sufficiently small, such that the time-domain Fresnel reflections have durations less than the round-trip time in the layers, the solution is unique and can be found by layer peeling. Numerical examples with dispersive and lossy media are given, demonstrating the usefulness of the method for e.g. THz technology.
Topological Structures in Rotating Stratified Flows
Redondo, J. M.; Carrillo, A.; Perez, E.
2003-04-01
Detailled 2D Particle traking and PIV visualizations performed on a series of large scale laboratory experiments at the Coriolis Platform of the SINTEF in Trondheim have revealed several resonances which scale on the Strouhal, the Rossby and the Richardson numbers. More than 100 experiments spanned a wide range of Rossby Deformation Radii and the topological structures (Parabolic /Eliptic /Hyperbolic) of the quasi-balanced stratified-rotating flows were studied when stirring (akin to coastal mixing) occured at a side of the tank. The strong asymetry favored by the total vorticity produces a wealth of mixing patterns.
Wang, Jianhua; Hansen, Elo Harald
2003-01-01
as substitutes for labor-intensive, manual, sample-pre-treatment and/or solution-handling procedures prior to analyte detection by inductively coupled plasma mass spectrometry (ICP-MS). The present review presents and discusses the progress of the state of the art in implementing miniaturized FI/SI systems...
Raposo, Francisco; Fernández-Cegrí, V.; De la Rubia, M.A.
2010-01-01
Chemical oxygen demand (COD) is a critical analytical parameter in waste and wastewater treatment, more specifically in anaerobic digestion, although little is known about the quality of measuring COD of anaerobic digestion samples. Proficiency testing (PT) is a powerful tool that can be used...
Paula Costa Mosca Macedo
2009-06-01
Full Text Available OBJECTIVE: To evaluate the quality of life during the first three years of training and identify its association with sociodemographicoccupational characteristics, leisure time and health habits. METHOD: A cross-sectional study with a random sample of 128 residents stratified by year of training was conducted. The Medical Outcome Study -short form 36 was administered. Mann-Whitney tests were carried out to compare percentile distributions of the eight quality of life domains, according to sociodemographic variables, and a multiple linear regression analysis was performed, followed by a validity checking for the resulting models. RESULTS: The physical component presented higher quality of life medians than the mental component. Comparisons between the three years showed that in almost all domains the quality of life scores of the second year residents were higher than the first year residents (p OBJETIVO: Avaliar a qualidade de vida do médico residente durante os três anos do treinamento e identificar sua associação com as características sociodemográficas-ocupacionais, tempo de lazer e hábitos de saúde. MÉTODO: Foi realizado um estudo transversal com amostra randomizada de 128 residentes, estratificada por ano de residência. O Medical Outcome Study-Short Form 36 foi aplicado; as distribuições percentis dos domínios de qualidade de vida de acordo com variáveis sociodemográficas foram analisadas pelo teste de Mann-Whitney e regressão linear múltipla, bem como estudo de validação pós-regressão. RESULTADOS: O componente físico da qualidade de vida apresentou medianas mais altas do que o mental. Comparações entre os três anos mostraram que quase todos os domínios de qualidade de vida tiveram escores maiores no segundo do que no primeiro ano (p < 0,01; em relação ao componente mental observamos maiores escores no terceiro ano do que nos demais (p < 0,01. Preditores de maior qualidade de vida foram: estar no segundo ou
René Roland Colditz
2015-07-01
Full Text Available Land cover mapping for large regions often employs satellite images of medium to coarse spatial resolution, which complicates mapping of discrete classes. Class memberships, which estimate the proportion of each class for every pixel, have been suggested as an alternative. This paper compares different strategies of training data allocation for discrete and continuous land cover mapping using classification and regression tree algorithms. In addition to measures of discrete and continuous map accuracy the correct estimation of the area is another important criteria. A subset of the 30 m national land cover dataset of 2006 (NLCD2006 of the United States was used as reference set to classify NADIR BRDF-adjusted surface reflectance time series of MODIS at 900 m spatial resolution. Results show that sampling of heterogeneous pixels and sample allocation according to the expected area of each class is best for classification trees. Regression trees for continuous land cover mapping should be trained with random allocation, and predictions should be normalized with a linear scaling function to correctly estimate the total area. From the tested algorithms random forest classification yields lower errors than boosted trees of C5.0, and Cubist shows higher accuracies than random forest regression.
Stratified growth in Pseudomonas aeruginosa biofilms
Werner, E.; Roe, F.; Bugnicourt, A.;
2004-01-01
In this study, stratified patterns of protein synthesis and growth were demonstrated in Pseudomonas aeruginosa biofilms. Spatial patterns of protein synthetic activity inside biofilms were characterized by the use of two green fluorescent protein (GFP) reporter gene constructs. One construct...... carried an isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible gfpmut2 gene encoding a stable GFP. The second construct carried a GFP derivative, gfp-AGA, encoding an unstable GFP under the control of the growth-rate-dependent rrnBp(1) promoter. Both GFP reporters indicated that active protein...... of oxygen limitation in the biofilm. Oxygen microelectrode measurements showed that oxygen only penetrated approximately 50 mum into the biofilm. P. aeruginosa was incapable of anaerobic growth in the medium used for this investigation. These results show that while mature P. aeruginosa biofilms contain...
Clustering of floating particles in stratified turbulence
Boffetta, Guido; de Lillo, Filippo; Musacchio, Stefano; Sozza, Alessandro
2016-11-01
We study the dynamics of small floating particles transported by stratified turbulence in presence of a mean linear density profile as a simple model for the confinement and the accumulation of plankton in the ocean. By means of extensive direct numerical simulations we investigate the statistical distribution of floaters as a function of the two dimensionless parameters of the problem. We find that vertical confinement of particles is mainly ruled by the degree of stratification, with a weak dependency on the particle properties. Conversely, small scale fractal clustering, typical of non-neutral particles in turbulence, depends on the particle relaxation time and is only weakly dependent on the flow stratification. The implications of our findings for the formation of thin phytoplankton layers are discussed.
On turbulence in a stratified environment
Sarkar, Sutanu
2015-11-01
John Lumley, motivated by atmospheric observations, made seminal contributions to the statistical theory (Lumley and Panofsky 1964, Lumley 1964) and second-order modeling (Zeman and Lumley 1976) of turbulence in the environment. Turbulent processes in the ocean share many features with the atmosphere, e.g., shear, stratification, rotation and rough topography. Results from direct and large eddy simulations of two model problems will be used to illustrate some of the features of turbulence in a stratified environment. The first problem concerns a shear layer in nonuniform stratification, a situation typical of both the atmosphere and the ocean. The second problem, considered to be responsible for much of the turbulent mixing that occurs in the ocean interior, concerns topographically generated internal gravity waves. Connections will be made to data taken during observational campaigns in the ocean.
Stratified scaffold design for engineering composite tissues.
Mosher, Christopher Z; Spalazzi, Jeffrey P; Lu, Helen H
2015-08-01
A significant challenge to orthopaedic soft tissue repair is the biological fixation of autologous or allogeneic grafts with bone, whereby the lack of functional integration between such grafts and host bone has limited the clinical success of anterior cruciate ligament (ACL) and other common soft tissue-based reconstructive grafts. The inability of current surgical reconstruction to restore the native fibrocartilaginous insertion between the ACL and the femur or tibia, which minimizes stress concentration and facilitates load transfer between the soft and hard tissues, compromises the long-term clinical functionality of these grafts. To enable integration, a stratified scaffold design that mimics the multiple tissue regions of the ACL interface (ligament-fibrocartilage-bone) represents a promising strategy for composite tissue formation. Moreover, distinct cellular organization and phase-specific matrix heterogeneity achieved through co- or tri-culture within the scaffold system can promote biomimetic multi-tissue regeneration. Here, we describe the methods for fabricating a tri-phasic scaffold intended for ligament-bone integration, as well as the tri-culture of fibroblasts, chondrocytes, and osteoblasts on the stratified scaffold for the formation of structurally contiguous and compositionally distinct regions of ligament, fibrocartilage and bone. The primary advantage of the tri-phasic scaffold is the recapitulation of the multi-tissue organization across the native interface through the layered design. Moreover, in addition to ease of fabrication, each scaffold phase is similar in polymer composition and therefore can be joined together by sintering, enabling the seamless integration of each region and avoiding delamination between scaffold layers.
Reconstruction of stratified steady water waves from pressure readings on the ocean bed
Chen, Robin Ming
2015-01-01
Consider a two-dimensional stratified solitary wave propagating through a body of water that is bounded below by an impermeable ocean bed. In this work, we study how such a wave can be reconstructed from data consisting of the wave speed, upstream and downstream density profile, and the trace of the pressure on the bed. First, we prove that this data uniquely determines the wave, both in the (real) analytic and Sobolev regimes. Second, for waves that consist of multiple layers of constant density immiscible fluids, we provide an exact formula describing each of the interfaces in terms of the data. Finally, for continuously stratified fluids, we detail a reconstruction scheme based on approximation by layer-wise constant density flows.
Magnetic flux concentrations from turbulent stratified convection
Käpylä, P J; Kleeorin, N; Käpylä, M J; Rogachevskii, I
2015-01-01
(abridged) Context: The mechanisms that cause the formation of sunspots are still unclear. Aims: We study the self-organisation of initially uniform sub-equipartition magnetic fields by highly stratified turbulent convection. Methods: We perform simulations of magnetoconvection in Cartesian domains that are $8.5$-$24$ Mm deep and $34$-$96$ Mm wide. We impose either a vertical or a horizontal uniform magnetic field in a convection-driven turbulent flow. Results: We find that super-equipartition magnetic flux concentrations are formed near the surface with domain depths of $12.5$ and $24$ Mm. The size of the concentrations increases as the box size increases and the largest structures ($20$ Mm horizontally) are obtained in the 24 Mm deep models. The field strength in the concentrations is in the range of $3$-$5$ kG. The concentrations grow approximately linearly in time. The effective magnetic pressure measured in the simulations is positive near the surface and negative in the bulk of the convection zone. Its ...
Asymptotic behavior of a stratified perturbation in a three dimensional expanding Universe
Fanelli, D
2002-01-01
The non-linear evolution of a stratified perturbation in a three dimensional expanding Universe is considered. A general Lagrangian scheme (Q model) is introduced and numerical investigations are performed. The asymptotic contraction of the core of the agglomeration is studied. A power-law scaling is detected and an heuristic interpretation of the numerical findings is provided. An asymptotic equation for the multi-stream velocity flow is derived and it is shown to agree quantitatively with the dynamics of the Q model. The relation to the adhesion model is discussed.
Optimal sampling schemes applied in geology
Debba, Pravesh
2010-05-01
Full Text Available , discuss the definition of hyperspectral versus multispectral, review some recent applications of hyperspectral image analysis, and summarize image-processing techniques commonly applied to hyperspectral imagery. Spectral Image Basics To understand...
Stratified spaces constitute a Fra\\"iss\\'e category
Mijares, José Gregorio
2010-01-01
We prove that stratified spaces and stratified pseudomanifolds satisfy categorical Fra\\"{\\i}ss\\'e properties. This result was presented for the First Meeting of Logic and Algebra in Bogot\\'a, on Sept. 2010. This article has been submitted to the Revista Colombiana de Matem\\'aticas.
Little, R; Wheeler, K; Edge, S
2017-02-11
This paper examines farmer attitudes towards the development of a voluntary risk-based trading scheme for cattle in England as a risk mitigation measure for bovine tuberculosis (bTB). The research reported here was commissioned to gather evidence on the type of scheme that would have a good chance of success in improving the information farmers receive about the bTB risk of cattle they buy. Telephone interviews were conducted with a stratified random sample of 203 cattle farmers in England, splitting the interviews equally between respondents in the high-risk area and low-risk area for bTB. Supplementary interviews and focus groups with farmers were also carried out across the risk areas. Results suggest a greater enthusiasm for a risk-based trading scheme in low-risk areas compared with high-risk areas and among members of breed societies and cattle health schemes. Third-party certification of herds by private vets or the Animal and Plant Health Agency were regarded as the most credible source, with farmer self-certification being favoured by sellers, but being regarded as least credible by buyers. Understanding farmers' attitudes towards voluntary risk-based trading is important to gauge likely uptake, understand preferences for information provision and to assist in monitoring, evaluating and refining the scheme once established.
Gas slug ascent through rheologically stratified conduits
Capponi, Antonio; James, Mike R.; Lane, Steve J.
2016-04-01
Textural and petrological evidence has indicated the presence of viscous, degassed magma layers at the top of the conduit at Stromboli. This layer acts as a plug through which gas slugs burst and it is thought to have a role in controlling the eruptive dynamics. Here, we present the results of laboratory experiments which detail the range of slug flow configurations that can develop in a rheologically stratified conduit. A gas slug can burst (1) after being fully accommodated within the plug volume, (2) whilst its base is still in the underlying low-viscosity liquid or (3) within a low-viscosity layer dynamically emplaced above the plug during the slug ascent. We illustrate the relevance of the same flow configurations at volcanic-scale through a new experimentally-validated 1D model and 3D computational fluid dynamic simulations. Applied to Stromboli, our results show that gas volume, plug thickness, plug viscosity and conduit radius control the transition between each configuration; in contrast, the configuration distribution seems insensitive to the viscosity of magma beneath the plug, which acts mainly to deliver the slug into the plug. Each identified flow configuration encompasses a variety of processes including dynamic narrowing and widening of the conduit, generation of instabilities along the falling liquid film, transient blockages of the slug path and slug break-up. All these complexities, in turn, lead to variations in the slug overpressure, mirrored by changes in infrasonic signatures which are also associated to different eruptive styles. Acoustic amplitudes are strongly dependent on the flow configuration in which the slugs burst, with both acoustic peak amplitudes and waveform shapes reflecting different burst dynamics. When compared to infrasonic signals from Stromboli, the similarity between real signals and laboratory waveforms suggests that the burst of a slug through a plug may represent a viable first-order mechanism for the generation of
Hameed, Omar; Humphrey, Peter A
2006-07-01
Typically glands of prostatic adenocarcinoma have a single cell lining, although stratification can be seen in invasive carcinomas with a cribriform architecture, including ductal carcinoma. The presence and diagnostic significance of stratified cells within non-cribriform carcinomatous prostatic glands has not been well addressed. The histomorphological features and immunohistochemical profile of cases of non-cribriform prostatic adenocarcinoma with stratified malignant glandular epithelium were analyzed. These cases were identified from needle biopsy cases from the consultation files of one of the authors and from a review of 150 consecutive in-house needle biopsy cases of prostatic adenocarcinoma. Immunohistochemistry was performed utilizing antibodies reactive against high molecular weight cytokeratin (34betaE12), p63 and alpha-methylacyl-coenzyme-A racemase (AMACR). A total of 8 cases were identified, including 2 from the 150 consecutive in-house cases (1.3%). In 4 cases, the focus with glands having stratified epithelium was the sole carcinomatous component in the biopsy, while such a component represented 5-30% of the invasive carcinoma seen elsewhere in the remaining cases. The main attribute in all these foci was the presence of glandular profiles lined by several layers of epithelial cells with cytological and architectural features resembling flat or tufted high-grade prostatic intraepithelial neoplasia, but lacking basal cells as confirmed by negative 34betaE12 and/or p63 immunostains in all cases. The AMACR staining profile of the stratified foci was variable, with 4 foci showing positivity, and 3 foci being negative, including two cases that displayed AMACR positivity in adjacent non-stratified prostatic adenocarcinoma. Prostatic adenocarcinoma with stratified malignant glandular epithelium can be identified in prostate needle biopsy samples harboring non-cribriform prostatic adenocarcinoma and resembles glands with high-grade prostatic
The Universal Aspect Ratio of Vortices in Rotating Stratifi?ed Flows: Experiments and Observations
Aubert, Oriane; Gal, Patrice Le; Marcus, Philip S
2012-01-01
We validate a new law for the aspect ratio $\\alpha = H/L$ of vortices in a rotating, stratified flow, where $H$ and $L$ are the vertical half-height and horizontal length scale of the vortices. The aspect ratio depends not only on the Coriolis parameter f and buoyancy (or Brunt-Vaisala) frequency $\\bar{N}$ of the background flow, but also on the buoyancy frequency $N_c$ within the vortex and on the Rossby number $Ro$ of the vortex such that $\\alpha = f \\sqrt{[Ro (1 + Ro)/(N_c^2- \\bar{N}^2)]}$. This law for $\\alpha$ is obeyed precisely by the exact equilibrium solution of the inviscid Boussinesq equations that we show to be a useful model of our laboratory vortices. The law is valid for both cyclones and anticyclones. Our anticyclones are generated by injecting fluid into a rotating tank filled with linearly-stratified salt water. The vortices are far from the top and bottom boundaries of the tank, so there is no Ekman circulation. In one set of experiments, the vortices viscously decay, but as they do, they c...
Sampling Theory of Food Safety System
LI, Bing; Chen, Guohua; Zhu, Ning
2009-01-01
We introduce the stratified sampling method, and put forward theoretical unbiased estimation of stratified sampling program, as well as the model and statistics of experimental design test. We also discuss the establishment of dietary exposure model, pollutant distribution model, and risk evaluation model. Finally, we present some methods for sampling design in China.
Sampling Theory of Food Safety System
Li, Bing; Chen, Guohua; Zhu, Ning
2009-01-01
We introduce the stratified sampling method, and put forward theoretical unbiased estimation of stratified sampling program, as well as the model and statistics of experimental design test. We also discuss the establishment of dietary exposure model, pollutant distribution model, and risk evaluation model. Finally, we present some methods for sampling design in China.
Sung, Yun Ju; Winkler, Thomas W; Manning, Alisa K; Aschard, Hugues; Gudnason, Vilmundur; Harris, Tamara B; Smith, Albert V; Boerwinkle, Eric; Brown, Michael R; Morrison, Alanna C; Fornage, Myriam; Lin, Li-An; Richard, Melissa; Bartz, Traci M; Psaty, Bruce M; Hayward, Caroline; Polasek, Ozren; Marten, Jonathan; Rudan, Igor; Feitosa, Mary F; Kraja, Aldi T; Province, Michael A; Deng, Xuan; Fisher, Virginia A; Zhou, Yanhua; Bielak, Lawrence F; Smith, Jennifer; Huffman, Jennifer E; Padmanabhan, Sandosh; Smith, Blair H; Ding, Jingzhong; Liu, Yongmei; Lohman, Kurt; Bouchard, Claude; Rankinen, Tuomo; Rice, Treva K; Arnett, Donna; Schwander, Karen; Guo, Xiuqing; Palmas, Walter; Rotter, Jerome I; Alfred, Tamuno; Bottinger, Erwin P; Loos, Ruth J F; Amin, Najaf; Franco, Oscar H; van Duijn, Cornelia M; Vojinovic, Dina; Chasman, Daniel I; Ridker, Paul M; Rose, Lynda M; Kardia, Sharon; Zhu, Xiaofeng; Rice, Kenneth; Borecki, Ingrid B; Rao, Dabeeru C; Gauderman, W James; Cupples, L Adrienne
2016-07-01
Studying gene-environment (G × E) interactions is important, as they extend our knowledge of the genetic architecture of complex traits and may help to identify novel variants not detected via analysis of main effects alone. The main statistical framework for studying G × E interactions uses a single regression model that includes both the genetic main and G × E interaction effects (the "joint" framework). The alternative "stratified" framework combines results from genetic main-effect analyses carried out separately within the exposed and unexposed groups. Although there have been several investigations using theory and simulation, an empirical comparison of the two frameworks is lacking. Here, we compare the two frameworks using results from genome-wide association studies of systolic blood pressure for 3.2 million low frequency and 6.5 million common variants across 20 cohorts of European ancestry, comprising 79,731 individuals. Our cohorts have sample sizes ranging from 456 to 22,983 and include both family-based and population-based samples. In cohort-specific analyses, the two frameworks provided similar inference for population-based cohorts. The agreement was reduced for family-based cohorts. In meta-analyses, agreement between the two frameworks was less than that observed in cohort-specific analyses, despite the increased sample size. In meta-analyses, agreement depended on (1) the minor allele frequency, (2) inclusion of family-based cohorts in meta-analysis, and (3) filtering scheme. The stratified framework appears to approximate the joint framework well only for common variants in population-based cohorts. We conclude that the joint framework is the preferred approach and should be used to control false positives when dealing with low-frequency variants and/or family-based cohorts.
Generalized Group Signature Scheme
无
2001-01-01
The concept of generalized group signature scheme will bepresent. Based on the generalized secret sharing scheme proposed by Lin and Ha rn, a non-interactive approach is designed for realizing such generalized group signature scheme. Using the new scheme, the authorized subsets of the group in w hich the group member can cooperate to produce the valid signature for any messa ge can be randomly specified
Sman, van der R.G.M.
2006-01-01
In the special case of relaxation parameter = 1 lattice Boltzmann schemes for (convection) diffusion and fluid flow are equivalent to finite difference/volume (FD) schemes, and are thus coined finite Boltzmann (FB) schemes. We show that the equivalence is inherent to the homology of the
Nørmark, Kurt
2010-01-01
A Scheme representation of Standard MIDI Files is proposed. The Scheme expressions are defined and constrained by an XML-language, which in the starting point is inspired by a MIDI XML event language made by the MIDI Manufactures Association. The representation of Standard MIDI Files in Scheme ma...
Nørmark, Kurt
2010-01-01
A Scheme representation of Standard MIDI Files is proposed. The Scheme expressions are defined and constrained by an XML-language, which in the starting point is inspired by a MIDI XML event language made by the MIDI Manufactures Association. The representation of Standard MIDI Files in Scheme ma...
Petit, J.L.
1997-07-21
This thesis is devoted to the inversion of VSP (vertical seismic profile) seismic data in order to determine the elastic properties of horizontally stratified media. The VSP records are computed using the full wave elastic modelling in isotropic and transversely isotropic media using Hankel transform, a finite difference scheme and an inverse Hankel transform algorithm, and the propagation equations are determined and numerically solved; the importance of considering a 3D wave propagation model instead of a 1 D one is emphasized. The theoretical VSP inverse problem is then considered, with the seismic waveform inversion set as a least-squares problem, consisting in recovering the distribution of physical parameters which minimize the misfit between calculated and observed VSP. The corresponding problem requires the knowledge of the source function
Scheme Program Documentation Tools
Nørmark, Kurt
2004-01-01
This paper describes and discusses two different Scheme documentation tools. The first is SchemeDoc, which is intended for documentation of the interfaces of Scheme libraries (APIs). The second is the Scheme Elucidator, which is for internal documentation of Scheme programs. Although the tools...... are separate and intended for different documentation purposes they are related to each other in several ways. Both tools are based on XML languages for tool setup and for documentation authoring. In addition, both tools rely on the LAML framework which---in a systematic way---makes an XML language available...
Hybrid scheme for Brownian semistationary processes
Bennedsen, Mikkel; Lunde, Asger; Pakkanen, Mikko S.
the asymptotics of the mean square error of the hybrid scheme and we observe that the scheme leads to a substantial improvement of accuracy compared to the ordinary forward Riemann-sum scheme, while having the same computational complexity. We exemplify the use of the hybrid scheme by two numerical experiments......, where we examine the finite-sample properties of an estimator of the roughness parameter of a Brownian semistationary process and study Monte Carlo option pricing in the rough Bergomi model of Bayer et al. (2015), respectively....
[Phylogenetic diversity of bacteria in soda lake stratified sediments].
Tourova, T P; Grechnikova, M A; Kuznetsov, V V; Sorokin, D Yu
2014-01-01
Various previously developed techniques for DNA extraction from the samples with complex physicochemical structure (soils, silts, and sediments) and modifications of these techniques developed in the present work were tested. Their usability for DNA extraction from the sediments of the Kulunda Steppe hypersaline soda lakes was assessed, and the most efficient procedure for indirect (two-stage) DNA extraction was proposed. Almost complete separation of the cell fraction was shown, as well as the inefficiency of nested PCR for analysis of the clone libraries obtained from washed sediments by amplification of the 16S rRNA gene fragments. Analysis of the clone library obtained from the cell fractions of stratified sediments (upper, medium, and lower layers) revealed that in the sediments of Lake Gorchina-3 most eubacterial phylotypes belonged to the class Clostridia, phylum Firmicutes. They were probably specific for this habitatand formed a new, presently unknown high-rank taxon. The data obtained revealed no pronounced stratification of the spe- cies diversity of the eubacterial component of the microbial community inhabiting the sediments (0-20 cm) in the inshore zone of Lake Gorchina-3.
Tangling clustering instability for small particles in temperature stratified turbulence
Elperin, Tov; Liberman, Michael; Rogachevskii, Igor
2013-01-01
We study particle clustering in a temperature stratified turbulence with small finite correlation time. It is shown that the temperature stratified turbulence strongly increases the degree of compressibility of particle velocity field. This results in the strong decrease of the threshold for the excitation of the tangling clustering instability even for small particles. The tangling clustering instability in the temperature stratified turbulence is essentially different from the inertial clustering instability that occurs in non-stratified isotropic and homogeneous turbulence. While the inertial clustering instability is caused by the centrifugal effect of the turbulent eddies, the mechanism of the tangling clustering instability is related to the temperature fluctuations generated by the tangling of the mean temperature gradient by the velocity fluctuations. Temperature fluctuations produce pressure fluctuations and cause particle clustering in regions with increased pressure fluctuations. It is shown that t...
Effects of rotation on turbulent buoyant plumes in stratified environments
Fabregat Tomàs, Alexandre; Poje, Andrew C; Özgökmen, Tamay M; Dewar, William K
2016-01-01
We numerically investigate the effects of rotation on the turbulent dynamics of thermally driven buoyant plumes in stratified environments at the large Rossby numbers characteristic of deep oceanic releases...
Numerical Study on Saltwater Instrusion in a Heterogeneous Stratified Aquifer
2000-01-01
In a costal aquifer, saltwater intrusion is frequently observed due to an excess exploitation. There are many researches focused on the saltwater intrusion. However, there are few researches, which take into consideration the mixing processes in a stratified heterogeneous aquifer. In the present study, a laboratory experiment and numerical simulation are made in order to understand the phenomena in a stratified heterogeneous aquifer. The result of the numerical analysis agrees well with the m...
Convertible Proxy Signcryption Scheme
李继国; 李建中; 曹珍富; 张亦辰
2004-01-01
In 1996, Mambo et al introduced the concept of proxy signature. However, proxy signature can only provide the delegated authenticity and cannot provide confidentiality. Recently, Gamage et al and Chan and Wei proposed different proxy signcryption schemes respectively, which extended the concept of proxy signature.However, only the specified receiver can decrypt and verify the validity of proxy signcryption in their schemes.To protect the receiver' s benefit in case of a later dispute, Wu and Hsu proposed a convertible authenticated encryption scheme, which carn enable the receiver to convert signature into an ordinary one that can be verified by anyone. Based on Wu and Hsu' s scheme and improved Kim' s scheme, we propose a convertible proxy signcryption scheme. The security of the proposed scheme is based on the intractability of reversing the one-way hash function and solving the discrete logarithm problem. The proposed scheme can satisfy all properties of strong proxy signature and withstand the public key substitution attack and does not use secure channel. In addition, the proposed scheme can be extended to convertible threshold proxy signcryption scheme.
Hansen, Elo Harald; Wang, Jianhua
2002-01-01
Various preconditioning procedures encomprising appropriate separation/preconcentration schemes in order to obtain optimal sensitivity and selectivity characteristics when using electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICPMS) are pres...
Hansen, Elo Harald; Wang, Jianhua
2002-01-01
Various preconditioning procedures encomprising appropriate separation/preconcentration schemes in order to obtain optimal sensitivity and selectivity characteristics when using electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICPMS) are pres......Various preconditioning procedures encomprising appropriate separation/preconcentration schemes in order to obtain optimal sensitivity and selectivity characteristics when using electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICPMS...... prior to detection are effected in a microconduit placed on top of an SI selection valve....
PROBABILITY SAMPLING DESIGNS FOR VETERINARY EPIDEMIOLOGY
Xhelil Koleci; Coryn, Chris L.S.; Kristin A. Hobson; Rruzhdi Keci
2011-01-01
The objective of sampling is to estimate population parameters, such as incidence or prevalence, from information contained in a sample. In this paper, the authors describe sources of error in sampling; basic probability sampling designs, including simple random sampling, stratified sampling, systematic sampling, and cluster sampling; estimating a population size if unknown; and factors influencing sample size determination for epidemiological studies in veterinary medicine.
Deepak Swami; P K Sharma; C S P Ojha
2014-12-01
In this paper, we have studied the behaviour of reactive solute transport through stratified porous medium under the influence of multi-process nonequilibrium transport model. Various experiments were carried out in the laboratory and the experimental breakthrough curves were observed at spatially placed sampling points for stratified porous medium. Batch sorption studies were also performed to estimate the sorption parameters of the material used in stratified aquifer system. The effects of distance dependent dispersion and tailing are visible in the experimental breakthrough curves. The presence of physical and chemical non-equilibrium are observed from the pattern of breakthrough curves. Multi-process non-equilibrium model represents the combined effect of physical and chemical non-ideality in the stratified aquifer system. The results show that the incorporation of distance dependent dispersivity in multi-process non-equilibrium model provides best fit of observed data through stratified porous media. Also, the exponential distance dependent dispersivity is more suitable for large distances and at small distances, linear or constant dispersivity function can be considered for simulating reactive solute in stratified porous medium.
Assessing iron dynamics in the release from a stratified reservoir
Ashby, S.L.; Faulkner, S.P.; Gambrell, R.P.; Smith, B.A.
2004-01-01
Field and laboratory studies were conducted to describe the fate of total, dissolved, and ferrous (Fe2.) iron in the release from a stratified reservoir with an anoxic hypolimnion. Concentrations of total iron in the tail water indicated a first order removal process during a low flow release (0.6 m3sec1), yet negligible loss was observed during a period of increased discharge (2.8 m 3 sec-1). Dissolved and ferrous iron concentrations in the tailwater were highly variable during both release regimes and did not follow responses based on theoretical predictions. Ferrous iron concentrations in unfiltered samples were consistently greater than concentrations observed in samples filtered separately through 0.4, 0.2, and 0.1 ??m filters. Total iron removal in laboratory studies followed first order kinetics, but was twice that rate (0.077 mg.L-1 .hr 1) observed during low flow discharge in the tailwater (0.036 mg. L1 .hr1). Dissolved and ferrous iron losses in laboratory studies were rapid (???75% in the first 15 minutes and 95% within 1 hour), followed theoretical predictions, and were much faster than observations in the tailwater (???30% within the first hour). The presence of particulate forms of ferrous iron in the field and differences in removal rates observed in field and laboratory studies indicate a need for improved field assessment techniques and consideration of complexation reactions when assessing the dynamics of iron in reservoir releases and downstream impacts as a result of operation regimes. ?? Copyright by the North American Lake Management Society 2004.
苗志敏; 赵世华; 王颜刚; 李长贵; 王忠超; 陈颖; 陈新焰; 阎胜利
2007-01-01
old in Shandong coastal area.DESIGN: A randomized, stratified cluster sampling survey.SETTING: D
Difference Schemes and Applications
2015-02-06
of the shallow water equations that is well suited for complex geometries and moving boundaries. Another (similar) regularization of...the solid wall extrapolation followed by the interpolation in the phase space (by solving the Riemann problem between the internal cell averages and...scheme. This Godunov-type scheme enjoys all major advantages of Riemann -problem-solver-free, non-oscillatory central schemes and, at the same time, have
Efficient Threshold Signature Scheme
Sattar J Aboud
2012-01-01
Full Text Available In this paper, we introduce a new threshold signature RSA-typed scheme. The proposed scheme has the characteristics of un-forgeable and robustness in random oracle model. Also, signature generation and verification is entirely non-interactive. In addition, the length of the entity signature participate is restricted by a steady times of the length of the RSA signature modulus. Also, the signing process of the proposed scheme is more efficient in terms of time complexity and interaction.
Stateless Transitive Signature Schemes
MA Chun-guang; CAI Man-chun; YANG Yi-xian
2004-01-01
A new practical method is introduced to transform the stateful transitive signature scheme to stateless one without the loss of security. According to the approach, two concrete stateless transitive signature schemes based on Factoring and RSA are presented respectively. Under the assumption of the hardness of factoring and one-more- RSA-inversion problem, both two schemes are secure under the adaptive chosen-message attacks in random oracle model.
Wald, Regina; Baumgartner, Martina; Urbantke, Verena; Stessl, Beatrix; Wittek, Thomas
2017-02-01
Bacteriological examination of milk samples is a prerequisite for pathogen-specific therapy and aids in limiting antimicrobial resistance. The aims of this study were to establish a standardized scheme for reliable Streptococcus uberis identification in routine diagnosis and to evaluate the accuracy of conventional tests and growing patterns of Strep. uberis on a selective medium (modified Rambach agar medium, MRAM) using 16S rRNA gene sequencing analysis as a reference method. We obtained isolates of presumptive Strep. uberis (n = 336) from quarter milk samples of dairy cows with intramammary infections and classified the isolates into 2 clusters using biochemical characterization. In cluster 1 (n = 280), cocci grew as non-hemolytic colonies, hydrolyzing esculin, carrying no Lancefield antigen (A/B/C/D/G) or Christie Atkins Munch-Petersen factor, and their growth was inhibited on an Enterococcus agar. Production of β-d-galactosidase on MRAM was shown by 257 of the cluster 1 isolates (91.79%), and 16S rRNA gene sequencing verified 271 (96.79%) of the isolates to be Strep. uberis. In 264 isolates (94.29%), MRAM agreed with the sequencing results. In cluster 2 (n = 56), isolates showed different characteristics: 37 (66.07%) were β-d-galactosidase-positive, and based on 16S sequencing results, 36 (64.29%) were identified correctly as Strep. uberis using biochemical methods. Identification success in this group differed significantly between routine diagnosis and MRAM application: MRAM agreed with sequencing results in 47 isolates (83.93%). To identify Strep. uberis and differentiate it from other lactic acid bacteria in routine diagnosis, we suggest using catalase reaction, hemolysis, esculin hydrolysis, and growth on enterococci agar. Isolates that show a typical biochemical profile can be identified satisfactorily with these tests. For Strep. uberis isolates with divergent patterns, application of MRAM as a follow-up test increased the diagnostic accuracy to 94
Kemp, Alan E. S.; Villareal, Tracy A.
2013-12-01
It is widely held that increased stratification and reduced vertical mixing in the ocean driven by global warming will promote the replacement of diatoms by smaller phytoplankton and lead to an overall decrease in productivity and carbon export. Here we present contrary evidence from a synergy of modern observations and palaeo-records that reveal high diatom production and export from stratified waters. Diatom adaptations to stratified waters include the ability to grow in low light conditions in deep chlorophyll maxima; vertical migrations between nutricline depths and the surface, and symbioses with N2-fixing cyanobacteria in diatom-diazotroph associations (DDA). These strategies foster the maintenance of seed populations that may then exploit mixing events induced by storms or eddies, but may also inherently promote blooms. Recent oceanographic observations in the subtropical gyres, at increasingly high temporal and spatial resolutions, have monitored short-lived but often substantial blooms and export of stratified-adapted diatoms including rhizosolenids and the diazotroph-associated Hemiaulus hauckii. Aggregate formation by such diatoms is common and promotes rapid settling thereby minimizing water column remineralization and optimizing carbon flux. Convergence zones associated with oceanic fronts or mesoscale features may also generate substantial flux of stratified-adapted diatom species. Conventional oceanographic observing strategies and sampling techniques under-represent such activity due to the lack of adequate capability to sample the large sized diatoms and colonies involved, the subsurface location of many of these blooms, their common development in thin global warming. However, the key genera involved in such potential feedbacks are underrepresented in both laboratory and field studies and are poorly represented in models. Our findings suggest that a reappraisal is necessary of the way diatoms are represented as plankton functional types (PFTs) in
Multiresolution signal decomposition schemes
J. Goutsias (John); H.J.A.M. Heijmans (Henk)
1998-01-01
textabstract[PNA-R9810] Interest in multiresolution techniques for signal processing and analysis is increasing steadily. An important instance of such a technique is the so-called pyramid decomposition scheme. This report proposes a general axiomatic pyramid decomposition scheme for signal analysis
Multiresolution signal decomposition schemes
Goutsias, J.; Heijmans, H.J.A.M.
1998-01-01
[PNA-R9810] Interest in multiresolution techniques for signal processing and analysis is increasing steadily. An important instance of such a technique is the so-called pyramid decomposition scheme. This report proposes a general axiomatic pyramid decomposition scheme for signal analysis and synthes
A new scoring system to stratify risk in unstable angina
Salzberg Simón
2003-08-01
Full Text Available Abstract Background We performed this study to develop a new scoring system to stratify different levels of risk in patients admitted to hospital with a diagnosis of unstable angina (UA, which is a complex syndrome that encompasses different outcomes. Many prognostic variables have been described but few efforts have been made to group them in order to enhance their individual predictive power. Methods In a first phase, 473 patients were prospectively analyzed to determine which factors were significantly associated with the in-hospital occurrence of refractory ischemia, acute myocardial infarction (AMI or death. A risk score ranging from 0 to 10 points was developed using a multivariate analysis. In a second phase, such score was validated in a new sample of 242 patients and it was finally applied to the entire population (n = 715. Results ST-segment deviation on the electrocardiogram, age ≥ 70 years, previous bypass surgery and troponin T ≥ 0.1 ng/mL were found as independent prognostic variables. A clear distinction was shown among categories of low, intermediate and high risk, defined according to the risk score. The incidence of the triple end-point was 6 %, 19.2 % and 44.7 % respectively, and the figures for AMI or death were 2 %, 11.4 % and 27.6 % respectively (p Conclusions This new scoring system is simple and easy to achieve. It allows a very good stratification of risk in patients having a clinical diagnosis of UA. They may be divided in three categories, which could be of help in the decision-making process.
Stability of stratified two-phase flows in horizontal channels
Barmak, Ilya; Ullmann, Amos; Brauner, Neima; Vitoshkin, Helen
2016-01-01
Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems the stratified flow with smooth interface is stable only in confined zone of relatively lo...
Background Oriented Schlieren in a Density Stratified Fluid
Verso, Lilly
2015-01-01
Non-intrusive quantitative fluid density measurements methods are essential in stratified flow experiments. Digital imaging leads to synthetic Schlieren methods in which the variations of the index of refraction are reconstructed computationally. In this study, an important extension to one of these methods, called Background Oriented Schlieren (BOS), is proposed. The extension enables an accurate reconstruction of the density field in stratified liquid experiments. Typically, the experiments are performed by the light source, background pattern, and the camera positioned on the opposite sides of a transparent vessel. The multi-media imaging through air-glass-water-glass-air leads to an additional aberration that destroys the reconstruction. A two-step calibration and image remapping transform are the key components that correct the images through the stratified media and provide non-intrusive full-field density measurements of transparent liquids.
Background oriented schlieren in a density stratified fluid
Verso, Lilly; Liberzon, Alex
2015-10-01
Non-intrusive quantitative fluid density measurement methods are essential in the stratified flow experiments. Digital imaging leads to synthetic schlieren methods in which the variations of the index of refraction are reconstructed computationally. In this study, an extension to one of these methods, called background oriented schlieren, is proposed. The extension enables an accurate reconstruction of the density field in stratified liquid experiments. Typically, the experiments are performed by the light source, background pattern, and the camera positioned on the opposite sides of a transparent vessel. The multimedia imaging through air-glass-water-glass-air leads to an additional aberration that destroys the reconstruction. A two-step calibration and image remapping transform are the key components that correct the images through the stratified media and provide a non-intrusive full-field density measurements of transparent liquids.
SINDA/FLUINT Stratified Tank Modeling for Cryrogenic Propellant Tanks
Sakowski, Barbara
2014-01-01
A general purpose SINDA/FLUINT (S/F) stratified tank model was created to simulate self-pressurization and axial jet TVS; Stratified layers in the vapor and liquid are modeled using S/F lumps.; The stratified tank model was constructed to permit incorporating the following additional features:, Multiple or singular lumps in the liquid and vapor regions of the tank, Real gases (also mixtures) and compressible liquids, Venting, pressurizing, and draining, Condensation and evaporation/boiling, Wall heat transfer, Elliptical, cylindrical, and spherical tank geometries; Extensive user logic is used to allow detailed tailoring - Don't have to rebuilt everything from scratch!!; Most code input for a specific case is done through the Registers Data Block:, Lump volumes are determined through user input:; Geometric tank dimensions (height, width, etc); Liquid level could be input as either a volume percentage of fill level or actual liquid level height
Fuel Burning Rate Model for Stratified Charge Engine
SONG Jin'ou; JIANG Zejun; YAO Chunde; WANG Hongfu
2006-01-01
A zero-dimensional single-zone double-curve model is presented to predict fuel burning rate in stratified charge engines, and it is integrated with GT-Power to predict the overall performance of the stratified charge engines.The model consists of two exponential functions for calculating the fuel burning rate in different charge zones.The model factors are determined by a non-linear curve fitting technique, based on the experimental data obtained from 30 cases in middle and low loads.The results show good agreement between the measured and calculated cylinder pressures,and the deviation between calculated and measured cylinder pressures is less than 5%.The zerodimensional single-zone double-curve model is successful in the combustion modeling for stratified charge engines.
Numerical Simulation on Stratified Flow over an Isolated Mountain Ridge
LI Ling; Shigeo Kimura
2007-01-01
The characteristics of stratified flow over an isolated mountain ridge have been investigated numerically. The two-dimensional model equations, based on the time-dependent Reynolds averaged NavierStokes equations, are solved numerically using an implicit time integration in a fitted body grid arrangement to simulate stratified flow over an isolated ideally bell-shaped mountain. The simulation results are in good agreement with the existing corresponding analytical and approximate solutions. It is shown that for atmospheric conditions where non-hydrostatic effects become dominant, the model is able to reproduce typical flow features. The dispersion characteristics of gaseous pollutants in the stratified flow have also been studied. The dispersion patterns for two typical atmospheric conditions are compared. The results show that the presence of a gravity wave causes vertical stratification of the pollutant concentration and affects the diffusive characteristics of the pollutants.
Stability of stratified two-phase flows in inclined channels
Barmak, Ilya; Ullmann, Amos; Brauner, Neima
2016-01-01
Linear stability of stratified gas-liquid and liquid-liquid plane-parallel flows in inclined channels is studied with respect to all wavenumber perturbations. The main objective is to predict parameter regions in which stable stratified configuration in inclined channels exists. Up to three distinct base states with different holdups exist in inclined flows, so that the stability analysis has to be carried out for each branch separately. Special attention is paid to the multiple solution regions to reveal the feasibility of non-unique stable stratified configurations in inclined channels. The stability boundaries of each branch of steady state solutions are presented on the flow pattern map and are accompanied by critical wavenumbers and spatial profiles of the most unstable perturbations. Instabilities of different nature are visualized by streamlines of the neutrally stable perturbed flows, consisting of the critical perturbation superimposed on the base flow. The present analysis confirms the existence of ...
A study of refraction of a cylindrical laser beam in stratified liquid
Rinkevichyus, B. S.; Sapronov, M. V.; Pavlov, I. N.
2016-09-01
Refraction of a cylindrical laser beam in a transition layer at the interface of two liquids with different optical characteristics is studied theoretically and experimentally. A theoretical basis for calculations of the beam trajectory in the transition layer of stratified liquid is given. Two- and three-dimensional images (2D and 3D refractograms) of a cylindrical laser beam inside and outside the media are obtained on the basis of a tangential model of the refractive index profile. The influence of the parameters of the laser beam and media on the appearance of refractograms is studied and the optimal experimental conditions are selected with the use of computer simulation. A scheme of the setup for recording digital 2D refractogram and experimental results are presented. Algorithms for digitizing experimental images and for their comparison with calculated refractograms to determine the refractive index profile in the transition layer based on the tangential model are developed.
Steady internal waves in an exponentially stratified two-layer fluid
Makarenko, Nikolay; Maltseva, Janna; Ivanova, Kseniya
2016-04-01
The problem on internal waves in a weakly stratified two-layered fluid is studied analytically. We suppose that the fluid possess exponential stratification in both the layers, and the fluid density has discontinuity jump at the interface. By that, we take into account the influence of weak continuous stratification outside of sharp pycnocline. The model equation of strongly nonlinear interfacial waves propagating along the pycnocline is considered. This equation extends approximate models [1-3] suggested for a two-layer fluid with one homogeneous layer. The derivation method uses asymptotic analysis of fully nonlinear Euler equations. The perturbation scheme involves the long wave procedure with a pair of the Boussinesq parameters. First of these parameters characterizes small density slope outside of pycnocline and the second one defines small density jump at the interface. Parametric range of solitary wave solutions is characterized, including extreme regimes such as plateau-shape solitary waves. This work was supported by RFBR (grant No 15-01-03942). References [1] N. Makarenko, J. Maltseva. Asymptotic models of internal stationary waves, J. Appl. Mech. Techn. Phys, 2008, 49(4), 646-654. [2] N. Makarenko, J. Maltseva. Phase velocity spectrum of internal waves in a weakly-stratified two-layer fluid, Fluid Dynamics, 2009, 44(2), 278-294. [3] N. Makarenko, J. Maltseva. An analytical model of large amplitude internal solitary waves, Extreme Ocean Waves, 2nd ed. Springer 2015, E.Pelinovsky and C.Kharif (Eds), 191-201.
Linear Inviscid Damping for Couette Flow in Stratified Fluid
Yang, Jincheng
2016-01-01
We study the inviscid damping of Coutte flow with an exponentially stratified density. The optimal decay rates of the velocity field and density are obtained for general perturbations with minimal regularity. For Boussinesq approximation model, the decay rates we get are consistent with the previous results in the literature. We also study the decay rates for the full equations of stratified fluids, which were not studied before. For both models, the decay rates depend on the Richardson number in a very similar way. Besides, we also study the inviscid damping of perturbations due to the exponential stratification when there is no shear.
Bases of Schur algebras associated to cellularly stratified diagram algebras
Bowman, C
2011-01-01
We examine homomorphisms between induced modules for a certain class of cellularly stratified diagram algebras, including the BMW algebra, Temperley-Lieb algebra, Brauer algebra, and (quantum) walled Brauer algebra. We define the `permutation' modules for these algebras, these are one-sided ideals which allow us to study the diagrammatic Schur algebras of Hartmann, Henke, Koenig and Paget. We construct bases of these Schur algebras in terms of modified tableaux. On the way we prove that the (quantum) walled Brauer algebra and the Temperley-Lieb algebra are both cellularly stratified and therefore have well-defined Specht filtrations.
Al-saggaf, Alawi A
2008-01-01
This paper attempt has been made to explain a fuzzy commitment scheme. In the conventional Commitment schemes, both committed string m and valid opening key are required to enable the sender to prove the commitment. However there could be many instances where the transmission involves noise or minor errors arising purely because of the factors over which neither the sender nor the receiver have any control. The fuzzy commitment scheme presented in this paper is to accept the opening key that is close to the original one in suitable distance metric, but not necessarily identical. The concept itself is illustrated with the help of simple situation.
van Haren, H.
2015-01-01
The character of turbulent overturns in a weakly stratified deep-sea is investigated in some detail using 144 high-resolution temperature sensors at 0.7 m intervals, starting 5 m above the bottom. A 9-day, 1 Hz sampled record from the 912 m depth flat-bottom (<0.5% bottom-slope) mooring site in the
van Haren, H.
2015-01-01
The character of turbulent overturns in a weakly stratified deep-sea is investigated in some detail using 144 high-resolution temperature sensors at 0.7 m intervals, starting 5 m above the bottom. A 9-day, 1 Hz sampled record from the 912 m depth flat-bottom (<0.5% bottom-slope) mooring site in the
Willcock, J J; Lumsdaine, A; Quinlan, D J
2008-08-19
Tabled execution is a generalization of memorization developed by the logic programming community. It not only saves results from tabled predicates, but also stores the set of currently active calls to them; tabled execution can thus provide meaningful semantics for programs that seemingly contain infinite recursions with the same arguments. In logic programming, tabled execution is used for many purposes, both for improving the efficiency of programs, and making tasks simpler and more direct to express than with normal logic programs. However, tabled execution is only infrequently applied in mainstream functional languages such as Scheme. We demonstrate an elegant implementation of tabled execution in Scheme, using a mix of continuation-passing style and mutable data. We also show the use of tabled execution in Scheme for a problem in formal language and automata theory, demonstrating that tabled execution can be a valuable tool for Scheme users.
Readout scheme of the upgraded ALICE TPC
Appelshaeuser, Harald; Ivanov, Marian; Lippmann, Christian; Wiechula, Jens
2016-01-01
In this document, we present the updated readout scheme for the ALICE TPC Upgrade. Two major design changes are implemented with respect to the concept that was presented in the TPC Upgrade Technical Design Report: – The SAMPA front-end ASIC will be used in direct readout mode. – The ADC sampling frequency will be reduced from 10 to 5 MHz. The main results from simulations and a description of the new readout scheme is outlined.
Analysis of photonic band-gap structures in stratified medium
Tong, Ming-Sze; Yinchao, Chen; Lu, Yilong;
2005-01-01
Purpose - To demonstrate the flexibility and advantages of a non-uniform pseudo-spectral time domain (nu-PSTD) method through studies of the wave propagation characteristics on photonic band-gap (PBG) structures in stratified medium Design/methodology/approach - A nu-PSTD method is proposed...
Plane Stratified Flow in a Room Ventilated by Displacement Ventilation
Nielsen, Peter Vilhelm; Nickel, J.; Baron, D. J. G.
2004-01-01
The air movement in the occupied zone of a room ventilated by displacement ventilation exists as a stratified flow along the floor. This flow can be radial or plane according to the number of wall-mounted diffusers and the room geometry. The paper addresses the situations where plane flow...
Bacterial production, protozoan grazing and mineralization in stratified lake Vechten.
Bloem, J.
1989-01-01
The role of heterotrophic nanoflagellates (HNAN, size 2-20 μm) in grazing on bacteria and mineralization of organic matter in stratified Lake Vechten was studied.Quantitative effects of manipulation and fixation on HNAN were checked. Considerable losses were caused by centrifugation, even at low spe
Population dynamics of sinking phytoplankton in stratified waters
Huisman, J.; Sommeijer, B.P.
2002-01-01
We analyze the predictions of a reaction-advection-diffusion model to pinpoint the necessary conditions for bloom development of sinking phytoplanktonspecies in stratified waters. This reveals that there are two parameter windows that can sustain sinking phytoplankton, a turbulence window and atherm
Gravity-induced stresses in stratified rock masses
Amadei, B.; Swolfs, H.S.; Savage, W.Z.
1988-01-01
This paper presents closed-form solutions for the stress field induced by gravity in anisotropic and stratified rock masses. These rocks are assumed to be laterally restrained. The rock mass consists of finite mechanical units, each unit being modeled as a homogeneous, transversely isotropic or isotropic linearly elastic material. The following results are found. The nature of the gravity induced stress field in a stratified rock mass depends on the elastic properties of each rock unit and how these properties vary with depth. It is thermodynamically admissible for the induced horizontal stress component in a given stratified rock mass to exceed the vertical stress component in certain units and to be smaller in other units; this is not possible for the classical unstratified isotropic solution. Examples are presented to explore the nature of the gravity induced stress field in stratified rock masses. It is found that a decrease in rock mass anisotropy and a stiffening of rock masses with depth can generate stress distributions comparable to empirical hyperbolic distributions previously proposed in the literature. ?? 1988 Springer-Verlag.
Dispersion of (light) inertial particles in stratified turbulence
van Aartrijk, M.; Clercx, H.J.H.; Armenio, Vincenzo; Geurts, Bernardus J.; Fröhlich, Jochen
2010-01-01
We present a brief overview of a numerical study of the dispersion of particles in stably stratified turbulence. Three types of particles arc examined: fluid particles, light inertial particles ($\\rho_p/\\rho_f = \\mathcal{O}(1)$) and heavy inertial particles ($\\rho_p/\\rho_f \\gg 1$). Stratification
The dynamics of small inertial particles in weakly stratified turbulence
van Aartrijk, M.; Clercx, H.J.H.
We present an overview of a numerical study on the small-scale dynamics and the large-scale dispersion of small inertial particles in stably stratified turbulence. Three types of particles are examined: fluid particles, light inertial particles (with particle-to-fluid density ratio 1Ͽp/Ͽf25) and
Characterization of Inlet Diffuser Performance for Stratified Thermal Storage
Cimbala, John M.; Bahnfleth, William; Song, Jing
1999-11-01
Storage of sensible heating or cooling capacity in stratified vessels has important applications in central heating and cooling plants, power production, and solar energy utilization, among others. In stratified thermal storage systems, diffusers at the top and bottom of a stratified tank introduce and withdraw fluid while maintaining a stable density gradient and causing as little mixing as possible. In chilled water storage applications, mixing during the formation of the thermocline near an inlet diffuser is the single greatest source of thermal losses. Most stratified chilled water storage tanks are cylindrical vessels with diffusers that are either circular disks that distribute flow radially outward or octagonal rings of perforated pipe that distribute flow both inward and outward radially. Both types produce gravity currents that are strongly influenced by the inlet Richardson number, but the significance of other parameters is not clear. The present investigation considers the dependence of the thermal performance of a perforated pipe diffuser on design parameters including inlet velocity, ambient and inlet fluid temperatures, and tank dimensions for a range of conditions representative of typical chilled water applications. Dimensional analysis is combined with a parametric study using results from computational fluid dynamics to obtain quantitative relationships between design parameters and expected thermal performance.
Diamessis, P.; Gurka, R.; Liberzon, A.
2008-11-01
Proper orthogonal decomposition (POD) is applied to 2-D slices of vorticity and horizontal divergence obtained from the 3-D DNS of the stratified turbulent wake of a towed sphere at Re=5x10^3 and Fr=4. Slices are sampled along the stream-depth (Oxz) and stream-span planes (Oxy) at 231 times during the interval Nt[12,35]. POD was chosen amongst the available statistical tools due to its advantage in characterization of simulated and experimentally measured velocity gradient fields, as previously demonstrated for turbulent boundary layers. In the Oxz planes, at the wake centerline, the higher most energetic modes reveal a structure similar of the structure of late-time stratified wakes. Off-set from centerline, the signature of internal waves in the form of forward-inclined coherent beams extending into the ambient becomes evident. The angle of inclination becomes progressively vertical with increasing POD mode. Lower POD modes on the Oyz planes show a layered structure in the wake core with coherent beams radiating out into the ambient over a broad range of angles. Further insight is provided through the relative energy spectra distribution of the vorticity eigenmodes. POD analysis has provided a statistical description of the geometrical features previously observed in instantaneous flow fields of stratified turbulent wakes.
Hanasoge, S M; Gizon, L
2010-01-01
Perfectly matched layers are a very efficient and accurate way to absorb waves in media. We present a stable convolutional unsplit perfectly matched formulation designed for the linearized stratified Euler equations. However, the technique as applied to the Magneto-hydrodynamic (MHD) equations requires the use of a sponge, which, despite placing the perfectly matched status in question, is still highly efficient at absorbing outgoing waves. We study solutions of the equations in the backdrop of models of linearized wave propagation in the Sun. We test the numerical stability of the schemes by integrating the equations over a large number of wave periods.
Recent progresses in outcome-dependent sampling with failure time data.
Ding, Jieli; Lu, Tsui-Shan; Cai, Jianwen; Zhou, Haibo
2017-01-01
An outcome-dependent sampling (ODS) design is a retrospective sampling scheme where one observes the primary exposure variables with a probability that depends on the observed value of the outcome variable. When the outcome of interest is failure time, the observed data are often censored. By allowing the selection of the supplemental samples depends on whether the event of interest happens or not and oversampling subjects from the most informative regions, ODS design for the time-to-event data can reduce the cost of the study and improve the efficiency. We review recent progresses and advances in research on ODS designs with failure time data. This includes researches on ODS related designs like case-cohort design, generalized case-cohort design, stratified case-cohort design, general failure-time ODS design, length-biased sampling design and interval sampling design.
DING XIU-HUAN; FU ZHI-GUO; ZHANG SHU-GONG
2009-01-01
This paper proposes an XTR version of the Kurosawa-Desmedt scheme. Our scheme is secure against adaptive choeen-ciphertext attack under the XTR version of the Decisional Diffie-Hellman assumption in the standard model. Comparing efficiency between the Kurosawa-Desmedt scheme and the proposed XTR-Kurosawa-Desmedt scheme, we find that the proposed scheme is more efficient than the Kurosawa-Desmedt scheme both in communication and computation without compromising security.
Juhl, Hans Jørn; Stacey, Julia
2001-01-01
It is usual practice to evaluate the success of a labelling scheme by looking at the awareness percentage, but in many cases this is not sufficient. The awareness percentage gives no indication of which of the consumer segments that are aware of and use labelling schemes and which do not. In the ......It is usual practice to evaluate the success of a labelling scheme by looking at the awareness percentage, but in many cases this is not sufficient. The awareness percentage gives no indication of which of the consumer segments that are aware of and use labelling schemes and which do not....... In the spring of 2001 MAPP carried out an extensive consumer study with special emphasis on the Nordic environmentally friendly label 'the swan'. The purpose was to find out how much consumers actually know and use various labelling schemes. 869 households were contacted and asked to fill in a questionnaire...... it into consideration when I go shopping. The respondent was asked to pick the most suitable answer, which described her use of each label. 29% - also called 'the labelling blind' - responded that they basically only knew the recycling label and the Government controlled organic label 'Ø-mærket'. Another segment of 6...
Placidi, M.; Jung, J. -Y.; Ratti, A.; Sun, C.
2014-07-25
This paper describes beam distribution schemes adopting a novel implementation based on low amplitude vertical deflections combined with horizontal ones generated by Lambertson-type septum magnets. This scheme offers substantial compactness in the longitudinal layouts of the beam lines and increased flexibility for beam delivery of multiple beam lines on a shot-to-shot basis. Fast kickers (FK) or transverse electric field RF Deflectors (RFD) provide the low amplitude deflections. Initially proposed at the Stanford Linear Accelerator Center (SLAC) as tools for beam diagnostics and more recently adopted for multiline beam pattern schemes, RFDs offer repetition capabilities and a likely better amplitude reproducibility when compared to FKs, which, in turn, offer more modest financial involvements both in construction and operation. Both solutions represent an ideal approach for the design of compact beam distribution systems resulting in space and cost savings while preserving flexibility and beam quality.
Towards Symbolic Encryption Schemes
Ahmed, Naveed; Jensen, Christian D.; Zenner, Erik
2012-01-01
Symbolic encryption, in the style of Dolev-Yao models, is ubiquitous in formal security models. In its common use, encryption on a whole message is specified as a single monolithic block. From a cryptographic perspective, however, this may require a resource-intensive cryptographic algorithm......, namely an authenticated encryption scheme that is secure under chosen ciphertext attack. Therefore, many reasonable encryption schemes, such as AES in the CBC or CFB mode, are not among the implementation options. In this paper, we report new attacks on CBC and CFB based implementations of the well......-known Needham-Schroeder and Denning-Sacco protocols. To avoid such problems, we advocate the use of refined notions of symbolic encryption that have natural correspondence to standard cryptographic encryption schemes....
Study of MRI in Stratified Viscous Plasma Configuration
Carlevaro, Nakia; Renzi, Fabrizio
2016-01-01
We analyze the morphology of the Magneto-rotational Instability (MRI) for a stratified viscous plasma disk configuration in differential rotation, taking into account the so-called corotation theorem for the background profile. In order to select the intrinsic Alfv\\'enic nature of MRI, we deal with an incompressible plasma and we adopt a formulation of the perturbation analysis based on the use of the magnetic flux function as a dynamical variable. Our study outlines, as consequence of the corotation condition, a marked asymmetry of the MRI with respect to the equatorial plane, particularly evident in a complete damping of the instability over a positive critical height on the equatorial plane. We also emphasize how such a feature is already present (although less pronounced) even in the ideal case, restoring a dependence of the MRI on the stratified morphology of the gravitational field.
FC-normal and extended stratified logic program
许道云; 丁德成
2002-01-01
This paper investigates the consistency property of FC-normal logic program and presentsan equivalent deciding condition whether a logic program P is an FC-normal program. The decidingcondition describes the characterizations of FC-normal program. By the Petri-net presentation ofa logic program, the characterizations of stratification of FC-normal program are investigated. Thestratification of FC-normal program motivates us to introduce a new kind of stratification, extendedstratification, over logic program. It is shown that an extended (locally) stratified logic program isan FC-normal program. Thus, an extended (locally) stratified logic program has at least one stablemodel. Finally, we have presented algorithms about computation of consistency property and a fewequivalent deciding methods of the finite FC-normal program.
Turbulent thermal diffusion in strongly stratified turbulence: theory and experiments
Amir, G; Eidelman, A; Elperin, T; Kleeorin, N; Rogachevskii, I
2016-01-01
Turbulent thermal diffusion is a combined effect of the temperature stratified turbulence and inertia of small particles. It causes the appearance of a non-diffusive turbulent flux of particles in the direction of the turbulent heat flux. This non-diffusive turbulent flux of particles is proportional to the product of the mean particle number density and the effective velocity of inertial particles. The theory of this effect has been previously developed only for small temperature gradients and small Stokes numbers (Phys. Rev. Lett. {\\bf 76}, 224, 1996). In this study a generalized theory of turbulent thermal diffusion for arbitrary temperature gradients and Stokes numbers has been developed. The laboratory experiments in the oscillating grid turbulence and in the multi-fan produced turbulence have been performed to validate the theory of turbulent thermal diffusion in strongly stratified turbulent flows. It has been shown that the ratio of the effective velocity of inertial particles to the characteristic ve...
Numerical Simulation of Wakes in a Weakly Stratified Fluid
Rottman, James W; Innis, George E; O'Shea, Thomas T; Novikov, Evgeny
2014-01-01
This paper describes some preliminary numerical studies using large eddy simulation of full-scale submarine wakes. Submarine wakes are a combination of the wake generated by a smooth slender body and a number of superimposed vortex pairs generated by various control surfaces and other body appendages. For this preliminary study, we attempt to gain some insight into the behavior of full-scale submarine wakes by computing separately the evolution the self-propelled wake of a slender body and the motion of a single vortex pair in both a non-stratified and a stratified environment. An important aspect of the simulations is the use of an iterative procedure to relax the initial turbulence field so that turbulent production and dissipation are in balance.
Helicity dynamics in stratified turbulence in the absence of forcing
Rorai, C; Pouquet, A; Mininni, P D
2012-01-01
A numerical study of decaying stably-stratified flows is performed. Relatively high stratification and moderate Reynolds numbers are considered, and a particular emphasis is placed on the role of helicity (velocity-vorticity correlations). The problem is tackled by integrating the Boussinesq equations in a periodic cubical domain using different initial conditions: a non-helical Taylor-Green (TG) flow, a fully helical Beltrami (ABC) flow, and random flows with a tunable helicity. We show that for stratified ABC flows helicity undergoes a substantially slower decay than for unstratified ABC flows. This fact is likely associated to the combined effect of stratification and large scale coherent structures. Indeed, when the latter are missing, as in random flows, helicity is rapidly destroyed by the onset of gravitational waves. A type of large-scale dissipative "cyclostrophic" balance can be invoked to explain this behavior. When helicity survives in the system it strongly affects the temporal energy decay and t...
Axisymmetric modes in vertically stratified self-gravitating discs
Mamatsashvili, George
2010-01-01
We perform linear analysis of axisymmetric vertical normal modes in stratified compressible self-gravitating polytropic discs in the shearing box approximation. We study specific dynamics for subadiabatic, adiabatic and superadiabatic vertical stratifications. In the absence of self-gravity, four well-known principal modes can be identified in a stratified disc: acoustic p-, surface gravity f-, buoyancy g- and inertial r-modes. After characterizing modes in the non-self-gravitating case, we include self-gravity and investigate how it modifies the properties of these modes. We find that self-gravity, to a certain degree, reduces their frequencies and changes the structure of the dispersion curves and eigenfunctions at radial wavelengths comparable to the disc height. Its influence on the basic branch of the r-mode, in the case of subadiabatic and adiabatic stratifications, and on the basic branch of the g-mode, in the case of superadiabatic stratification (which in addition exhibits convective instability), do...
Elementary stratified flows with stability at low Richardson number
Barros, Ricardo [Mathematics Applications Consortium for Science and Industry (MACSI), Department of Mathematics and Statistics, University of Limerick, Limerick (Ireland); Choi, Wooyoung [Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102-1982 (United States)
2014-12-15
We revisit the stability analysis for three classical configurations of multiple fluid layers proposed by Goldstein [“On the stability of superposed streams of fluids of different densities,” Proc. R. Soc. A. 132, 524 (1931)], Taylor [“Effect of variation in density on the stability of superposed streams of fluid,” Proc. R. Soc. A 132, 499 (1931)], and Holmboe [“On the behaviour of symmetric waves in stratified shear layers,” Geophys. Publ. 24, 67 (1962)] as simple prototypes to understand stability characteristics of stratified shear flows with sharp density transitions. When such flows are confined in a finite domain, it is shown that a large shear across the layers that is often considered a source of instability plays a stabilizing role. Presented are simple analytical criteria for stability of these low Richardson number flows.
Royle, J. Andrew; Converse, Sarah J.
2014-01-01
Capture–recapture studies are often conducted on populations that are stratified by space, time or other factors. In this paper, we develop a Bayesian spatial capture–recapture (SCR) modelling framework for stratified populations – when sampling occurs within multiple distinct spatial and temporal strata.We describe a hierarchical model that integrates distinct models for both the spatial encounter history data from capture–recapture sampling, and also for modelling variation in density among strata. We use an implementation of data augmentation to parameterize the model in terms of a latent categorical stratum or group membership variable, which provides a convenient implementation in popular BUGS software packages.We provide an example application to an experimental study involving small-mammal sampling on multiple trapping grids over multiple years, where the main interest is in modelling a treatment effect on population density among the trapping grids.Many capture–recapture studies involve some aspect of spatial or temporal replication that requires some attention to modelling variation among groups or strata. We propose a hierarchical model that allows explicit modelling of group or strata effects. Because the model is formulated for individual encounter histories and is easily implemented in the BUGS language and other free software, it also provides a general framework for modelling individual effects, such as are present in SCR models.
2006-01-01
We study the question of ``how robust are the known lower bounds of labeling schemes when one increases the number of consulted labels''. Let $f$ be a function on pairs of vertices. An $f$-labeling scheme for a family of graphs $\\cF$ labels the vertices of all graphs in $\\cF$ such that for every graph $G\\in\\cF$ and every two vertices $u,v\\in G$, the value $f(u,v)$ can be inferred by merely inspecting the labels of $u$ and $v$. This paper introduces a natural generalization: the notion of $f$-...
Experiments on the dryout behavior of stratified debris beds
Leininger, Simon; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)
2015-10-15
In case of a severe accident with loss of coolant and core meltdown a particle bed (debris) can be formed. The removal of decay heat from the debris bed is of prime importance for the bed's long-term coolability to guarantee the integrity of the RPV. In contrast to previous experiments, the focus is on stratified beds. The experiments have pointed out that the bed's coolability is significantly affected.
Computation of mixing in large stably stratified enclosures
Zhao, Haihua
This dissertation presents a set of new numerical models for the mixing and heat transfer problems in large stably stratified enclosures. Basing on these models, a new computer code, BMIX++ (Berkeley mechanistic MIXing code in C++), was developed by Christensen (2001) and the author. Traditional lumped control volume methods and zone models cannot model the detailed information about the distributions of temperature, density, and pressure in enclosures and therefore can have significant errors. 2-D and 3-D CFD methods require very fine grid resolution to resolve thin substructures such as jets, wall boundaries, yet such fine grid resolution is difficult or impossible to provide due to computational expense. Peterson's scaling (1994) showed that stratified mixing processes in large stably stratified enclosures can be described using one-dimensional differential equations, with the vertical transport by free and wall jets modeled using standard integral techniques. This allows very large reductions in computational effort compared to three-dimensional numerical modeling of turbulent mixing in large enclosures. The BMIX++ code was developed to implement the above ideas. The code uses a Lagrangian approach to solve 1-D transient governing equations for the ambient fluid and uses analytical models or 1-D integral models to compute substructures. 1-D transient conduction model for the solid boundaries, pressure computation and opening models are also included to make the code more versatile. The BMIX++ code was implemented in C++ and the Object-Oriented-Programming (OOP) technique was intensively used. The BMIX++ code was successfully applied to different types of mixing problems such as stratification in a water tank due to a heater inside, water tank exchange flow experiment simulation, early stage building fire analysis, stratification produced by multiple plumes, and simulations for the UCB large enclosure experiments. Most of these simulations gave satisfying
A statistical mechanics approach to mixing in stratified fluids
Venaille, A.; Gostiaux, L.; Sommeria, J.
2017-01-01
Predicting how much mixing occurs when a given amount of energy is injected into a Boussinesq fluid is a longstanding problem in stratified turbulence. The huge number of degrees of freedom involved in those processes renders extremely difficult a deterministic approach to the problem. Here we present a statistical mechanics approach yielding prediction for a cumulative, global mixing efficiency as a function of a global Richardson number and the background buoyancy profile.
Corticosteroids and pediatric septic shock outcomes: a risk stratified analysis.
Sarah J Atkinson
Full Text Available The potential benefits of corticosteroids for septic shock may depend on initial mortality risk.We determined associations between corticosteroids and outcomes in children with septic shock who were stratified by initial mortality risk.We conducted a retrospective analysis of an ongoing, multi-center pediatric septic shock clinical and biological database. Using a validated biomarker-based stratification tool (PERSEVERE, 496 subjects were stratified into three initial mortality risk strata (low, intermediate, and high. Subjects receiving corticosteroids during the initial 7 days of admission (n = 252 were compared to subjects who did not receive corticosteroids (n = 244. Logistic regression was used to model the effects of corticosteroids on 28-day mortality and complicated course, defined as death within 28 days or persistence of two or more organ failures at 7 days.Subjects who received corticosteroids had greater organ failure burden, higher illness severity, higher mortality, and a greater requirement for vasoactive medications, compared to subjects who did not receive corticosteroids. PERSEVERE-based mortality risk did not differ between the two groups. For the entire cohort, corticosteroids were associated with increased risk of mortality (OR 2.3, 95% CI 1.3-4.0, p = 0.004 and a complicated course (OR 1.7, 95% CI 1.1-2.5, p = 0.012. Within each PERSEVERE-based stratum, corticosteroid administration was not associated with improved outcomes. Similarly, corticosteroid administration was not associated with improved outcomes among patients with no comorbidities, nor in groups of patients stratified by PRISM.Risk stratified analysis failed to demonstrate any benefit from corticosteroids in this pediatric septic shock cohort.
Dust particle charge distribution in a stratified glow discharge
Sukhinin, Gennady I [Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Lavrentyev Ave., 1, Novosibirsk 630090 (Russian Federation); Fedoseev, Alexander V [Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Lavrentyev Ave., 1, Novosibirsk 630090 (Russian Federation); Ramazanov, Tlekkabul S [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan); Dzhumagulova, Karlygash N [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan); Amangaliyeva, Rauan Zh [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan)
2007-12-21
The influence of a highly pronounced non-equilibrium characteristic of the electron energy distribution function in a stratified dc glow discharge on the process of dust particle charging in a complex plasma is taken into account for the first time. The calculated particle charge spatial distribution is essentially non-homogeneous and it can explain the vortex motion of particles at the periphery of a dusty cloud obtained in experiments.
Stability of stratified two-phase flows in inclined channels
Barmak, I.; Gelfgat, A. Yu.; Ullmann, A.; Brauner, N.
2016-08-01
Linear stability of the stratified gas-liquid and liquid-liquid plane-parallel flows in the inclined channels is studied with respect to all wavenumber perturbations. The main objective is to predict the parameter regions in which the stable stratified configuration in inclined channels exists. Up to three distinct base states with different holdups exist in the inclined flows, so that the stability analysis has to be carried out for each branch separately. Special attention is paid to the multiple solution regions to reveal the feasibility of the non-unique stable stratified configurations in inclined channels. The stability boundaries of each branch of the steady state solutions are presented on the flow pattern map and are accompanied by the critical wavenumbers and the spatial profiles of the most unstable perturbations. Instabilities of different nature are visualized by the streamlines of the neutrally stable perturbed flows, consisting of the critical perturbation superimposed on the base flow. The present analysis confirms the existence of two stable stratified flow configurations in a region of low flow rates in the countercurrent liquid-liquid flows. These configurations become unstable with respect to the shear mode of instability. It was revealed that in slightly upward inclined flows the lower and middle solutions for the holdup are stable in the part of the triple solution region, while the upper solution is always unstable. In the case of downward flows, in the triple solution region, none of the solutions are stable with respect to the short-wave perturbations. These flows are stable only in the single solution region at low flow rates of the heavy phase, and the long-wave perturbations are the most unstable ones.
Thermal stratification built up in hot water tank with different inlet stratifiers
Dragsted, Janne; Furbo, Simon; Dannemand, Mark
2017-01-01
H is a rigid plastic pipe with holes for each 30 cm. The holes are designed with flaps preventing counter flow into the pipe. The inlet stratifier from EyeCular Technologies ApS is made of a flexible polymer with openings all along the side and in the full length of the stratifier. The flexibility...... in order to elucidate how well thermal stratification is established in the tank with differently designed inlet stratifiers under different controlled laboratory conditions. The investigated inlet stratifiers are from Solvis GmbH & Co KG and EyeCular Technologies ApS. The inlet stratifier from Solvis Gmb...... of the stratifier prevents counterflow. The tests have shown that both types of inlet stratifiers had an ability to create stratification in the test tank under the different test conditions. The stratifier from EyeCular Technologies ApS had a better performance at low flows of 1-2 l/min and the stratifier...
Stability of stratified two-phase flows in horizontal channels
Barmak, I.; Gelfgat, A.; Vitoshkin, H.; Ullmann, A.; Brauner, N.
2016-04-01
Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems, the stratified flow with a smooth interface is stable only in confined zone of relatively low flow rates, which is in agreement with experiments, but is not predicted by long-wave analysis. Depending on the flow conditions, the critical perturbations can originate mainly at the interface (so-called "interfacial modes of instability") or in the bulk of one of the phases (i.e., "shear modes"). The present analysis revealed that there is no definite correlation between the type of instability and the perturbation wavelength.
Continuous Dependence on the Density for Stratified Steady Water Waves
Chen, Robin Ming; Walsh, Samuel
2016-02-01
There are two distinct regimes commonly used to model traveling waves in stratified water: continuous stratification, where the density is smooth throughout the fluid, and layer-wise continuous stratification, where the fluid consists of multiple immiscible strata. The former is the more physically accurate description, but the latter is frequently more amenable to analysis and computation. By the conservation of mass, the density is constant along the streamlines of the flow; the stratification can therefore be specified by prescribing the value of the density on each streamline. We call this the streamline density function. Our main result states that, for every smoothly stratified periodic traveling wave in a certain small-amplitude regime, there is an L ∞ neighborhood of its streamline density function such that, for any piecewise smooth streamline density function in that neighborhood, there is a corresponding traveling wave solution. Moreover, the mapping from streamline density function to wave is Lipschitz continuous in a certain function space framework. As this neighborhood includes piecewise smooth densities with arbitrarily many jump discontinues, this theorem provides a rigorous justification for the ubiquitous practice of approximating a smoothly stratified wave by a layered one. We also discuss some applications of this result to the study of the qualitative features of such waves.
Survival analysis of cervical cancer using stratified Cox regression
Purnami, S. W.; Inayati, K. D.; Sari, N. W. Wulan; Chosuvivatwong, V.; Sriplung, H.
2016-04-01
Cervical cancer is one of the mostly widely cancer cause of the women death in the world including Indonesia. Most cervical cancer patients come to the hospital already in an advanced stadium. As a result, the treatment of cervical cancer becomes more difficult and even can increase the death's risk. One of parameter that can be used to assess successfully of treatment is the probability of survival. This study raises the issue of cervical cancer survival patients at Dr. Soetomo Hospital using stratified Cox regression based on six factors such as age, stadium, treatment initiation, companion disease, complication, and anemia. Stratified Cox model is used because there is one independent variable that does not satisfy the proportional hazards assumption that is stadium. The results of the stratified Cox model show that the complication variable is significant factor which influent survival probability of cervical cancer patient. The obtained hazard ratio is 7.35. It means that cervical cancer patient who has complication is at risk of dying 7.35 times greater than patient who did not has complication. While the adjusted survival curves showed that stadium IV had the lowest probability of survival.
Alternative health insurance schemes
Keiding, Hans; Hansen, Bodil O.
2002-01-01
In this paper, we present a simple model of health insurance with asymmetric information, where we compare two alternative ways of organizing the insurance market. Either as a competitive insurance market, where some risks remain uninsured, or as a compulsory scheme, where however, the level...... competitive insurance; this situation turns out to be at least as good as either of the alternatives...
董秀芳; 肖武; 赵彬
2012-01-01
分析了高大洁净厂房的空间特点、使用时间特点、净化负荷特点,提出了在高度上分层的净化空调方案.采用CFD模拟了某高大洁净厂房采用分层净化空调时的气流组织,浓度场、温度场的模拟结果表明,该方案适用于高大洁净厂房.%Analyses the characteristics of space, service time and cleaning load in the building, and provides the stratified cleaning air conditioning scheme. Simulates the air distribution of stratified cleaning air conditioning in a large-space clean factory building with CFD. The concentration and temperature fields obtained show that the stratified cleaning air conditioning scheme suits for large-space clean factory buildings.
Jet-mixing of initially-stratified liquid-liquid pipe flows: experiments and numerical simulations
Wright, Stuart; Ibarra-Hernandes, Roberto; Xie, Zhihua; Markides, Christos; Matar, Omar
2016-11-01
Low pipeline velocities lead to stratification and so-called 'phase slip' in horizontal liquid-liquid flows due to differences in liquid densities and viscosities. Stratified flows have no suitable single point for sampling, from which average phase properties (e.g. fractions) can be established. Inline mixing, achieved by static mixers or jets in cross-flow (JICF), is often used to overcome liquid-liquid stratification by establishing unstable two-phase dispersions for sampling. Achieving dispersions in liquid-liquid pipeline flows using JICF is the subject of this experimental and modelling work. The experimental facility involves a matched refractive index liquid-liquid-solid system, featuring an ETFE test section, and experimental liquids which are silicone oil and a 51-wt% glycerol solution. The matching then allows the dispersed fluid phase fractions and velocity fields to be established through advanced optical techniques, namely PLIF (for phase) and PTV or PIV (for velocity fields). CFD codes using the volume of a fluid (VOF) method are then used to demonstrate JICF breakup and dispersion in stratified pipeline flows. A number of simple jet configurations are described and their dispersion effectiveness is compared with the experimental results. Funding from Cameron for Ph.D. studentship (SW) gratefully acknowledged.
On Converting Secret Sharing Scheme to Visual Secret Sharing Scheme
Wang Daoshun
2010-01-01
Full Text Available Abstract Traditional Secret Sharing (SS schemes reconstruct secret exactly the same as the original one but involve complex computation. Visual Secret Sharing (VSS schemes decode the secret without computation, but each share is m times as big as the original and the quality of the reconstructed secret image is reduced. Probabilistic visual secret sharing (Prob.VSS schemes for a binary image use only one subpixel to share the secret image; however the probability of white pixels in a white area is higher than that in a black area in the reconstructed secret image. SS schemes, VSS schemes, and Prob. VSS schemes have various construction methods and advantages. This paper first presents an approach to convert (transform a -SS scheme to a -VSS scheme for greyscale images. The generation of the shadow images (shares is based on Boolean XOR operation. The secret image can be reconstructed directly by performing Boolean OR operation, as in most conventional VSS schemes. Its pixel expansion is significantly smaller than that of VSS schemes. The quality of the reconstructed images, measured by average contrast, is the same as VSS schemes. Then a novel matrix-concatenation approach is used to extend the greyscale -SS scheme to a more general case of greyscale -VSS scheme.
Rapaka, Narsimha R.; Sarkar, Sutanu
2016-10-01
A sharp-interface Immersed Boundary Method (IBM) is developed to simulate density-stratified turbulent flows in complex geometry using a Cartesian grid. The basic numerical scheme corresponds to a central second-order finite difference method, third-order Runge-Kutta integration in time for the advective terms and an alternating direction implicit (ADI) scheme for the viscous and diffusive terms. The solver developed here allows for both direct numerical simulation (DNS) and large eddy simulation (LES) approaches. Methods to enhance the mass conservation and numerical stability of the solver to simulate high Reynolds number flows are discussed. Convergence with second-order accuracy is demonstrated in flow past a cylinder. The solver is validated against past laboratory and numerical results in flow past a sphere, and in channel flow with and without stratification. Since topographically generated internal waves are believed to result in a substantial fraction of turbulent mixing in the ocean, we are motivated to examine oscillating tidal flow over a triangular obstacle to assess the ability of this computational model to represent nonlinear internal waves and turbulence. Results in laboratory-scale (order of few meters) simulations show that the wave energy flux, mean flow properties and turbulent kinetic energy agree well with our previous results obtained using a body-fitted grid (BFG). The deviation of IBM results from BFG results is found to increase with increasing nonlinearity in the wave field that is associated with either increasing steepness of the topography relative to the internal wave propagation angle or with the amplitude of the oscillatory forcing. LES is performed on a large scale ridge, of the order of few kilometers in length, that has the same geometrical shape and same non-dimensional values for the governing flow and environmental parameters as the laboratory-scale topography, but significantly larger Reynolds number. A non-linear drag law
Magnetic Field in the Gravitationally Stratified Coronal Loops
B. N. Dwivedi; A. K. Srivastava
2015-03-01
We study the effect of gravitational stratification on the estimation of magnetic fields in the coronal loops. By using the method of MHD seismology of kink waves for the estimation of magnetic field of coronal loops, we derive a new formula for the magnetic field considering the effect of gravitational stratification. The fast-kink wave is a potential diagnostic tool for the estimation of magnetic field in fluxtubes. We consider the eleven kink oscillation cases observed by TRACE between July 1998 and June 2001. We calculate magnetic field in the stratified loops (str) and compare them with the previously calculated absolute magnetic field (abs). The gravitational stratification efficiently affects the magnetic field estimation in the coronal loops as it affects also the properties of kink waves. We find ≈22% increment in the magnetic field for the smallest ( = 72 Mm) while ≈42% increment in the absolute magnetic field for the longest ( = 406 Mm) coronal loops. The magnetic fields str and abs also increase with the number density, if the loop length does not vary much. The increment in the magnetic field due to gravitational stratification is small at the lower number densities, however, it is large at the higher number densities. We find that damping time of kink waves due to phase-mixing is less in the case of gravitationally stratified loops compared to nonstratified ones. This indicates the more rapid damping of kink waves in the stratified loops. In conclusion, we find that the gravitational stratification efficiently affects the estimation of magnetic field and damping time estimation especially in the longer coronal loops.
Experimental Study of Fluorine Transport Rules in Unsaturated Stratified Soil
ZHANG Hong-mei; SU Bao-yu; LIU Peng-hua; ZHANG Wei
2007-01-01
With the aid of soil column test models, the transport rules of fluorine contaminants in unsaturated stratified soils are discussed. Curves of F- concentrations at different times and sites in the unsaturated stratified soil were obtained under conditions of continuous injection of fluoride contaminants and water. Based on the analysis of the actual observation data, the values between computed results and observed data were compared. It is shown that the chemical properties of fluorine ions are active. The migration process of fluorine ions in soils is complex. Because of the effect of adsorption and desorption, the curve of the fluorine ion breakthrough curve is not symmetric. Its concentration peak value at each measuring point gradually decays. The tail of the breakthrough curve is long and the process of leaching and purifying using water requires considerable time. Along with the release of OHˉ in the process of fluorine absorption, the pH value of the soil solution changed from neutral to alkalinity during the test process. The first part of the breakthrough curve fitted better than the second part. The main reason is that fluorine does not always exist in the form of fluorinions in groundwater. Given the long test time, fluorinions possibly react with other ions in the soil solution to form complex water-soluble fluorine compounds. Only the retardation factor and source-sink term have been considered in our numerical model, which may leads to errors of computed values. But as a whole the migration rules of fluorine ions are basically correct, which indicates that the established numerical model can be used to simulate the transport rules of fluorine contaminants in unsaturated stratified soils.
Stratified spin-up in a sliced, square cylinder
Munro, R. J. [Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Foster, M. R. [Department of Mathematical Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)
2014-02-15
We previously reported experimental and theoretical results on the linear spin-up of a linearly stratified, rotating fluid in a uniform-depth square cylinder [M. R. Foster and R. J. Munro, “The linear spin-up of a stratified, rotating fluid in a square cylinder,” J. Fluid Mech. 712, 7–40 (2012)]. Here we extend that analysis to a “sliced” square cylinder, which has a base-plane inclined at a shallow angle α. Asymptotic results are derived that show the spin-up phase is achieved by a combination of the Ekman-layer eruptions (from the perimeter region of the cylinder's lid and base) and cross-slope-propagating stratified Rossby waves. The final, steady state limit for this spin-up phase is identical to that found previously for the uniform depth cylinder, but is reached somewhat more rapidly on a time scale of order E{sup −1/2}Ω{sup −1}/log (α/E{sup 1/2}) (compared to E{sup −1/2}Ω{sup −1} for the uniform-depth cylinder), where Ω is the rotation rate and E the Ekman number. Experiments were performed for Burger numbers, S, between 0.4 and 16, and showed that for S≳O(1), the Rossby modes are severely damped, and it is only at small S, and during the early stages, that the presence of these wave modes was evident. These observations are supported by the theory, which shows the damping factors increase with S and are numerically large for S≳O(1)
2013-01-01
Background Antibiograms created by aggregating hospital-wide susceptibility data from diverse patients can be misleading. To demonstrate the utility of age- and location-stratified antibiograms, we compared stratified antibiograms for three common bacterial pathogens, E. coli, S. aureus, and S. pneumoniae. We created stratified antibiograms based on patient age (/=65 years), and inpatient or outpatient location using all 2009 E. coli and S. aureus, and all 2008–2009 S. pneumoniae isolates sub...
Electromagnetic fields due to dipole antennas over stratified anisotropic media.
Kong, J. A.
1972-01-01
Solutions to the problem of radiation of dipole antennas in the presence of a stratified anisotropic media are facilitated by decomposing a general wave field into transverse magnetic (TM) and transverse electric (TE) modes. Employing the propagation matrices, wave amplitudes in any region are related to those in any other regions. The reflection coefficients, which embed all the information about the geometrical configuration and the physical constituents of the medium, are obtained in closed form. In view of the general formulation, various special cases are discussed.
Instabilities developed in stratified flows over pronounced obstacles
Varela, J.; Araújo, M.; Bove, I.; Cabeza, C.; Usera, G.; Martí, Arturo C.; Montagne, R.; Sarasúa, L. G.
2007-12-01
In the present work we study numerical and experimentally the flow of a two-layer stratified fluid over a topographic obstacle. The problem reflects a wide number of oceanographic and meteorological situations, where the stratification plays an important role. We identify the different instabilities developed by studying the pycnocline deformation due to a pronounced obstacle. The numerical simulations were made using the model caffa3D.MB which works with a numerical model of Navier-Stokes equations with finite volume elements in curvilinear meshes. The experimental results are contrasted with numerical simulations. Linear stability analysis predictions are checked with particle image velocimetry (PIV) measurements.
Stratified waveguide grating coupler for normal fiber incidence.
Wang, Bin; Jiang, Jianhua; Chambers, Diana M; Cai, Jingbo; Nordin, Gregory P
2005-04-15
We propose a new stratified waveguide grating coupler (SWGC) to couple light from a fiber at normal incidence into a planar waveguide. SWGCs are designed to operate in the strong coupling regime without intermediate optics between the fiber and the waveguide. Two-dimensional finite-difference time-domain simulation in conjunction with microgenetic algorithm optimization shows that approximately 72% coupling efficiency is possible for fiber (core size of 8.3 microm and delta=0.36%) to slab waveguide (1.2-microm core and delta=3.1%) coupling. We show that the phase-matching and Bragg conditions are simultaneously satisfied through the fundamental leaky mode.
Magnetorotational instability in weakly ionised, stratified accretion discs
Salmeron, Roberto Aureliano; Salmeron, Raquel; Wardle, Mark
2003-01-01
The magnetorotational instability (MRI) (Balbus and Hawley 1991, Hawley and Balbus 1991) transports angular momentum radially outwards in accretion discs through the distortion of the magnetic field lines that connect fluid elements. In protostellar discs, low conductivity is important, especially in the inner regions (Gammie 1996, Wardle 1997). As a result, low k modes are relevant and vertical stratification is a key factor of the analysis. However, most models of the MRI in these environments have adopted either the ambipolar diffusion or resistive approximations and have not simultaneously treated stratification and Hall conductivity. We present here a linear analysis of the MRI, including the Hall effect, in a stratified disc.
Enhanced charge transport kinetics in anisotropic, stratified photoanodes.
Yazdani, Nuri; Bozyigit, Deniz; Utke, Ivo; Buchheim, Jakob; Youn, Seul Ki; Patscheider, Jörg; Wood, Vanessa; Park, Hyung Gyu
2014-02-12
The kinetics of charge transport in mesoporous photoanodes strongly constrains the design and power conversion efficiencies of dye sensitized solar cells (DSSCs). Here, we report a stratified photoanode design with enhanced kinetics achieved through the incorporation of a fast charge transport intermediary between the titania and charge collector. Proof of concept photoanodes demonstrate that the inclusion of the intermediary not only enhances effective diffusion coefficients but also significantly suppresses charge recombination, leading to diffusion lengths two orders of magnitude greater than in standard mesoporous titania photoanodes. The intermediary concept holds promise for higher-efficiency DSSCs.
Abd Wahab Siti Rashidah Hanum
2016-01-01
Full Text Available High-rise residential building is a type of housing that has multi-dwelling units built on the same land. This type of housing has become popular each year in urban area due to the increasing cost of land. There are several common facilities provided in high-rise residential building. For example playground, swimming pool, gymnasium, 24 hours security system such as CCTV, access card and so on. Thus, maintenance works of the common facilities must be well organised. The purpose of this paper is to identify the classification of facilities provided at high rise residential building. The survey was done on 170 high-rise residential schemes by using stratified random sampling technique. The scope of this research is within Klang Valley area. This area is rapidly developed with high-rise residential building. The objective of this survey is to list down all the facilities provided in each sample of the schemes. The result, there are nine classification of facilities provided for high-rise residential building.
A log rank type test in observational survival studies with stratified sampling.
Bai, Xiaofei; Tsiatis, Anastasios A
2016-04-01
In randomized clinical trials, the log rank test is often used to test the null hypothesis of the equality of treatment-specific survival distributions. In observational studies, however, the ordinary log rank test is no longer guaranteed to be valid. In such studies we must be cautious about potential confounders; that is, the covariates that affect both the treatment assignment and the survival distribution. In this paper, two cases were considered: the first is when it is believed that all the potential confounders are captured in the primary database, and the second case where a substudy is conducted to capture additional confounding covariates. We generalize the augmented inverse probability weighted complete case estimators for treatment-specific survival distribution proposed in Bai et al. (Biometrics 69:830-839, 2013) and develop the log rank type test in both cases. The consistency and double robustness of the proposed test statistics are shown in simulation studies. These statistics are then applied to the data from the observational study that motivated this research.
A-Stratified Computerized Adaptive Testing with Unequal Item Exposure across Strata.
Deng, Hui; Chang, Hua-Hua
The purpose of this study was to compare a proposed revised a-stratified, or alpha-stratified, USTR method of test item selection with the original alpha-stratified multistage computerized adaptive testing approach (STR) and the use of maximum Fisher information (FSH) with respect to test efficiency and item pool usage using simulated computerized…
Penetrative convection in stratified fluids: velocity and temperature measurements
M. Moroni
2006-01-01
Full Text Available The flux through the interface between a mixing layer and a stable layer plays a fundamental role in characterizing and forecasting the quality of water in stratified lakes and in the oceans, and the quality of air in the atmosphere. The evolution of the mixing layer in a stably stratified fluid body is simulated in the laboratory when "Penetrative Convection" occurs. The laboratory model consists of a tank filled with water and subjected to heating from below. The methods employed to detect the mixing layer growth were thermocouples for temperature data and two image analysis techniques, namely Laser Induced Fluorescence (LIF and Feature Tracking (FT. LIF allows the mixing layer evolution to be visualized. Feature Tracking is used to detect tracer particle trajectories moving within the measurement volume. Pollutant dispersion phenomena are naturally described in the Lagrangian approach as the pollutant acts as a tag of the fluid particles. The transilient matrix represents one of the possible tools available for quantifying particle dispersion during the evolution of the phenomenon.
STRESS DISTRIBUTION IN THE STRATIFIED MASS CONTAINING VERTICAL ALVEOLE
Bobileva Tatiana Nikolaevna
2017-08-01
Full Text Available Almost all subsurface rocks used as foundations for various types of structures are stratified. Such heterogeneity may cause specific behaviour of the materials under strain. Differential equations describing the behaviour of such materials contain rapidly fluctuating coefficients, in view of this, solution of such equations is more time-consuming when using today’s computers. The method of asymptotic averaging leads to getting homogeneous medium under study to averaged equations with fixed factors. The present article is concerned with stratified soil mass consisting of pair-wise alternative isotropic elastic layers. In the results of elastic modules averaging, the present soil mass with horizontal rock stratification is simulated by homogeneous transversal-isotropic half-space with isotropy plane perpendicular to the standing axis. Half-space is loosened by a vertical alveole of circular cross-section, and virgin ground is under its own weight. For horizontal parting planes of layers, the following two types of surface conditions are set: ideal contact and backlash without cleavage. For homogeneous transversal-isotropic half-space received with a vertical alveole, the analytical solution of S.G. Lekhnitsky, well known in scientific papers, is used. The author gives expressions for stress components and displacements in soil mass for different marginal conditions on the alveole surface. Such research problems arise when constructing and maintaining buildings and when composite materials are used.
Stability of steam-water countercurrent stratified flow
Lee, S C
1985-10-01
Two flow instabilities which limit the normal condensation processes in countercurrent stratified steam-water flow have been identified experimentally: flooding and condensation-induced waterhammer. In order to initiate condensation-induced waterhammer in nearly horizontal or moderately-inclined steam/subcooled-water flow, two conditions, the appearance of a wavy interface and complete condensation of the incoming steam, are necessary. Analyses of these conditions are performed on a basis of flow stability and heat transfer considerations. Flooding data for several inclinations and channel heights are collected. Effects of condensation, inclination angle and channel height on the flooding characteristics are discussed. An envelope theory for the onset of flooding in inclined stratified flow is developed, which agrees well with the experimental data. Some empirical information on basic flow parameters, such as mean film thickness and interfacial friction factor required for this theory are measured. The previous viewpoints on flooding appear not to conflict with the present experimental data in nearly horizontal flow but the flooding phenomena in nearly vertical flow appear to be more complicated than those described by these viewpoints because of liquid droplet entrainment.
Strongly Stratified Turbulence Wakes and Mixing Produced by Fractal Wakes
Dimitrieva, Natalia; Redondo, Jose Manuel; Chashechkin, Yuli; Fraunie, Philippe; Velascos, David
2017-04-01
This paper describes Shliering and Shadowgraph experiments of the wake induced mixing produced by tranversing a vertical or horizontal fractal grid through the interfase between two miscible fluids at low Atwood and Reynolds numbers. This is a configuration design to models the mixing across isopycnals in stably-stratified flows in many environmental relevant situations (either in the atmosphere or in the ocean. The initial unstable stratification is characterized by a reduced gravity: g' = gΔρ ρ where g is gravity, Δρ being the initial density step and ρ the reference density. Here the Atwood number is A = g' _ 2 g . The topology of the fractal wake within the strong stratification, and the internal wave field produces both a turbulent cascade and a wave cascade, with frecuen parametric resonances, the envelope of the mixing front is found to follow a complex non steady 3rd order polinomial function with a maximum at about 4-5 Brunt-Vaisalla non-dimensional time scales: t/N δ = c1(t/N) + c2g Δρ ρ (t/N)2 -c3(t/N)3. Conductivity probes and Shliering and Shadowgraph visual techniques, including CIV with (Laser induced fluorescence and digitization of the light attenuation across the tank) are used in order to investigate the density gradients and the three-dimensionality of the expanding and contracting wake. Fractal analysis is also used in order to estimate the fastest and slowest growing wavelengths. The large scale structures are observed to increase in wave-length as the mixing progresses, and the processes involved in this increase in scale are also examined.Measurements of the pointwise and horizontally averaged concentrations confirm the picture obtained from past flow visualization studies. They show that the fluid passes through the mixing region with relatively small amounts of molecular mixing,and the molecular effects only dominate on longer time scales when the small scales have penetrated through the large scale structures. The Non
Wagner, Stephan; Legros, Samuel; Löschner, Katrin
2015-01-01
The applicability of a multi-step generic procedure to systematically develop sample preparation methods for the detection, characterization, and quantification of inorganic engineered nanoparticles (ENPs) in a complex matrix was successfully demonstrated. The research focused on the optimization...... content by asymmetric flow-field flow fractionation coupled to a multi-angle light scattering detector and an inductively coupled plasma mass spectrometer. Following the proposed generic procedure SiO2-ENPs were separated from a tomato soup. Two potential sample preparation methods were tested these being...
Bonus schemes and trading activity
Pikulina, E.S.; Renneboog, L.D.R.; ter Horst, J.R.; Tobler, P.N.
2014-01-01
Little is known about how different bonus schemes affect traders' propensity to trade and which bonus schemes improve traders' performance. We study the effects of linear versus threshold bonus schemes on traders' behavior. Traders buy and sell shares in an experimental stock market on the basis of
Bonus Schemes and Trading Activity
Pikulina, E.S.; Renneboog, L.D.R.; Ter Horst, J.R.; Tobler, P.N.
2013-01-01
Abstract: Little is known about how different bonus schemes affect traders’ propensity to trade and which bonus schemes improve traders’ performance. We study the effects of linear versus threshold (convex) bonus schemes on traders’ behavior. Traders purchase and sell shares in an experimental stock
Bonus schemes and trading activity
Pikulina, E.S.; Renneboog, L.D.R.; ter Horst, J.R.; Tobler, P.N.
2014-01-01
Little is known about how different bonus schemes affect traders' propensity to trade and which bonus schemes improve traders' performance. We study the effects of linear versus threshold bonus schemes on traders' behavior. Traders buy and sell shares in an experimental stock market on the basis of
Two Improved Digital Signature Schemes
无
2001-01-01
In this paper, two improved digital signature schemes are presented based on the design of directed signaturescheme [3]. The peculiarity of the system is that only if the scheme is specific recipient, the signature is authenticated.Since the scheme adds the screen of some information parameters, the difficulty of deciphered keys and the security ofdigital signature system are increased.
CONSIDERATIONS CONCERNING GUARANTEE SCHEMES
EMILIA CLIPICI
2013-05-01
Full Text Available When a large withdrawal from banks occurs, customers withdraw their deposits, so banks are likely to go bankrupt because of liquidity problems. There are several mechanisms that allow the banking system to avoid the phenomenon of massive withdrawals from banks. The most effective one is the deposit insurance. The deposit insurance is seen primarily as a means of protecting depositors of credit institutions, and secondly as a means of ensuring the stability of the banking system. This article described deposit guarantee scheme in Romania and other country.
An Improved Interpolative Vector Quantization Scheme for Image Compression
Ms. Darshana Chaware
2013-05-01
Full Text Available The aim of this paper is to develop a new image compression scheme by introducing visual patterns to interpolative vector quantization (IVQ. In this scheme first input images are down-sampled by ideal filter. Then, the down sampled images are compressed lossly by JPEG and transmitted to the decoder. In the decoder side, the decoded images are first up-sampled to the original resolution. The codebook is designed using LBG algorithm. We introduce visual patterns on designing the codebook. Experiment results shows that our scheme achieves much better performance over JPEG in terms of visual quality and PSNR
Hansen, Elo Harald; Wang, Jianhua
Despite their excellent analytical chemical capacities, ETAAS and ICPMS, nevertheless, often require suitable pretreatment of the sample material in order to obtain the necessary sensitivity and selectivity. Either in order to separate/preconcentrate the analyte material, or because of the presen...
Dolgin, Madlena; Einziger, Pinchas D
2010-05-01
Image reconstruction in electrical impedance tomography is, generally, an ill-posed nonlinear inverse problem. Regularization methods are widely used to ensure a stable solution. Herein, we present a case study, which uses a novel electrical impedance tomography method for reconstruction of layered biological tissues with piecewise continuous plane-stratified profiles. The algorithm implements the recently proposed reconstruction scheme for piecewise constant conductivity profiles, utilizing Legendre expansion in conjunction with improved Prony method. It is shown that the proposed algorithm is capable of successfully reconstructing piecewise continuous conductivity profiles with moderate slop. This reconstruction procedure, which calculates both the locations and the conductivities, repetitively provides inhomogeneous depth discretization, i.e., the depths grid is not equispaced. Incorporation of this specific inhomogeneous grid in the widely used mean least square reconstruction procedure results in a stable and accurate reconstruction, whereas, the commonly selected equispaced depth grid leads to unstable reconstruction. This observation establishes the main result of our investigation, highlighting the impact of physical phenomenon (the image series expansion) on electrical impedance tomography, leading to a physically motivated stabilization of the inverse problem, i.e., an inhomogeneous depth discretization renders an inherent regularization of the mean least square algorithm. The effectiveness and the significance of inhomogeneous discretization in electrical impedance tomography reconstruction procedure is further demonstrated and verified via numerical simulations.
Martizzi, Davide; Faucher-Giguere, Claude-Andre; Quataert, Eliot
2016-01-01
We use local Cartesian simulations with a vertical gravitational potential to study how supernova (SN) feedback in stratified galactic discs drives turbulence and launches galactic winds. Our analysis includes three disc models with gas surface densities ranging from Milky Way-like galaxies to gas-rich ultra-luminous infrared galaxies (ULIRGs), and two different SN driving schemes (random and correlated with local gas density). In order to isolate the physics of SN feedback, we do not include additional feedback processes. We find that, in these local box calculations, SN feedback excites relatively low mass-weighted gas turbulent velocity dispersions ~3-7 km/s and low wind mass loading factors <1 in all the cases we study. The low turbulent velocities and wind mass loading factors predicted by our local box calculations are significantly below those suggested by observations of gas-rich and rapidly star-forming galaxies; they are also in tension with global simulations of disc galaxies regulated by stella...
Geostatistics for Mapping Leaf Area Index over a Cropland Landscape: Efficiency Sampling Assessment
Javier Garcia-Haro
2010-11-01
Full Text Available This paper evaluates the performance of spatial methods to estimate leaf area index (LAI fields from ground-based measurements at high-spatial resolution over a cropland landscape. Three geostatistical model variants of the kriging technique, the ordinary kriging (OK, the collocated cokriging (CKC and kriging with an external drift (KED are used. The study focused on the influence of the spatial sampling protocol, auxiliary information, and spatial resolution in the estimates. The main advantage of these models lies in the possibility of considering the spatial dependence of the data and, in the case of the KED and CKC, the auxiliary information for each location used for prediction purposes. A high-resolution NDVI image computed from SPOT TOA reflectance data is used as an auxiliary variable in LAI predictions. The CKC and KED predictions have proven the relevance of the auxiliary information to reproduce the spatial pattern at local scales, proving the KED model to be the best estimator when a non-stationary trend is observed. Advantages and limitations of the methods in LAI field predictions for two systematic and two stratified spatial samplings are discussed for high (20 m, medium (300 m and coarse (1 km spatial scales. The KED has exhibited the best observed local accuracy for all the spatial samplings. Meanwhile, the OK model provides comparable results when a well stratified sampling scheme is considered by land cover.
Secure mediated certificateless signature scheme
YANG Chen; MA Wen-ping; WANG Xin-mei
2007-01-01
Ju et al proposed a certificateless signature scheme with instantaneous revocation by introducing security mediator (SEM) mechanism. This article presents a detailed cryptoanalysis of this scheme and shows that, in their proposed scheme, once a valid signature has been produced, the signer can recover his private key information and the instantaneous revocation property will be damaged. Furthermore, an improved mediated signature scheme, which can eliminate these disadvantages, is proposed, and security proof of the improved scheme under elliptic curve factorization problem (ECFP) assumption and bilinear computational diffie-hellman problem (BCDH) assumption is also proposed.
Balcazar G, M.; Flores R, J.H
1992-01-15
As part of the knowledge about the radiometric surface exploration, carried out in the geothermal field of Chipilapa, El Salvador, its were considered the geo-statistical parameters starting from the calculated variogram of the field data, being that the maxim distance of correlation of the samples in 'radon' in the different observation addresses (N-S, E-W, N W-S E, N E-S W), it was of 121 mts for the monitoring grill in future prospectus in the same area. Being derived of it an optimization (minimum cost) in the spacing of the field samples by means of geo-statistical techniques, without losing the detection of the anomaly. (Author)
Hydrodynamics of stratified epithelium: steady state and linearized dynamics
Yeh, Wei-Ting
2015-01-01
A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue is assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description for tissue dynamics at long-wavelength, long-time limit is developed, and the analysis reveals important insight for the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface could enhance small perturbations. This destabilizing mechanism is general for continuous self-renewal multi-layered tissues, it could be related to the origin of certain tissue morphology and developing pattern.
Hydrodynamics of stratified epithelium: Steady state and linearized dynamics
Yeh, Wei-Ting; Chen, Hsuan-Yi
2016-05-01
A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.
Local Radiation MHD Instabilities in Magnetically Stratified Media
Tao, Ted
2011-01-01
We study local radiation magnetohydrodynamic instabilities in static, optically thick, vertically stratified media with constant flux mean opacity. We include the effects of vertical gradients in a horizontal background magnetic field. Assuming rapid radiative diffusion, we use the zero gas pressure limit as an entry point for investigating the coupling between the photon bubble instability and the Parker instability. Apart from factors that depend on wavenumber orientation, the Parker instability exists for wavelengths longer than a characteristic wavelength lambda_{tran}, while photon bubbles exist for wavelengths shorter than lambda_{tran}. The growth rate in the Parker regime is independent of the orientation of the horizontal component of the wavenumber when radiative diffusion is rapid, but the range of Parker-like wavenumbers is extended if there exists strong horizontal shear between field lines (i.e. horizontal wavenumber perpendicular to the magnetic field). Finite gas pressure introduces an additio...
The Risk-Stratified Osteoporosis Strategy Evaluation study (ROSE)
Rubin, Katrine Hass; Holmberg, Teresa; Rothmann, Mette Juel
2015-01-01
The risk-stratified osteoporosis strategy evaluation study (ROSE) is a randomized prospective population-based study investigating the effectiveness of a two-step screening program for osteoporosis in women. This paper reports the study design and baseline characteristics of the study population....... 35,000 women aged 65-80 years were selected at random from the population in the Region of Southern Denmark and-before inclusion-randomized to either a screening group or a control group. As first step, a self-administered questionnaire regarding risk factors for osteoporosis based on FRAX......(®) was issued to both groups. As second step, subjects in the screening group with a 10-year probability of major osteoporotic fractures ≥15 % were offered a DXA scan. Patients diagnosed with osteoporosis from the DXA scan were advised to see their GP and discuss pharmaceutical treatment according to Danish...
Short-wave vortex instability in stratified flow
Bovard, Luke
2014-01-01
In this paper we investigate a new instability of the Lamb-Chaplygin dipole in a stratified fluid. Through numerical linear stability analysis, a secondary peak in the growth rate emerges at vertical scales about an order of magnitude smaller than the buoyancy scale $L_{b}=U/N$ where $U$ is the characteristic velocity and $N$ is the Brunt-V\\"{a}is\\"{a}l\\"{a} frequency. This new instability exhibits a growth rate that is similar to, and even exceeds, that of the zigzag instability, which has the characteristic length of the buoyancy scale. This instability is investigated for a wide range of Reynolds $Re=2000-20000$ and horizontal Froude numbers $F_{h}=0.05-0.2$, where $F_{h}=U/NR$, $Re=UR/\
Internal combustion engine using premixed combustion of stratified charges
Marriott, Craig D.; Reitz, Rolf D. (Madison, WI
2003-12-30
During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.
A study of stratified gas-liquid pipe flow
Johnson, George W.
2005-07-01
This work includes both theoretical modelling and experimental observations which are relevant to the design of gas condensate transport lines. Multicomponent hydrocarbon gas mixtures are transported in pipes over long distances and at various inclinations. Under certain circumstances, the heavier hydrocarbon components and/or water vapour condense to form one or more liquid phases. Near the desired capacity, the liquid condensate and water is efficiently transported in the form of a stratified flow with a droplet field. During operating conditions however, the flow rate may be reduced allowing liquid accumulation which can create serious operational problems due to large amounts of excess liquid being expelled into the receiving facilities during production ramp-up or even in steady production in severe cases. In particular, liquid tends to accumulate in upward inclined sections due to insufficient drag on the liquid from the gas. To optimize the transport of gas condensates, a pipe diameters should be carefully chosen to account for varying flow rates and pressure levels which are determined through the knowledge of the multiphase flow present. It is desirable to have a reliable numerical simulation tool to predict liquid accumulation for various flow rates, pipe diameters and pressure levels which is not presently accounted for by industrial flow codes. A critical feature of the simulation code would include the ability to predict the transition from small liquid accumulation at high flow rates to large liquid accumulation at low flow rates. A semi-intermittent flow regime of roll waves alternating with a partly backward flowing liquid film has been observed experimentally to occur for a range of gas flow rates. Most of the liquid is transported in the roll waves. The roll wave regime is not well understood and requires fundamental modelling and experimental research. The lack of reliable models for this regime leads to inaccurate prediction of the onset of
Turbulent reconnection of magnetic bipoles in stratified turbulence
Jabbari, Sarah; Mitra, Dhrubaditya; Kleeorin, Nathan; Rogachevskii, Igor
2016-01-01
We consider strongly stratified forced turbulence in a plane-parallel layer with helicity and corresponding large-scale dynamo action in the lower part and nonhelical turbulence in the upper. The magnetic field is found to develop strongly concentrated bipolar structures near the surface. They form elongated bands with a sharp interface between opposite polarities. Unlike earlier experiments with imposed magnetic field, the inclusion of rotation does not strongly suppress the formation of these structures. We perform a systematic numerical study of this phenomenon by varying magnetic Reynolds number, scale separation ratio, and Coriolis number. We also focus on the formation of the current sheet between bipolar regions where reconnection of oppositely oriented field lines occurs. We determine the reconnection rate by measuring either the inflow velocity in the vicinity of the current sheet or by measuring the electric field in the reconnection region. We demonstrate that for small Lundquist number, S1000, the...
Inertial modes of non-stratified superfluid neutron stars
Prix, R; Andersson, N
2004-01-01
We present results concerning adiabatic inertial-mode oscillations of non-stratified superfluid neutron stars in Newtonian gravity, using the anelastic and slow-rotation approximations. We consider a simple two-fluid model of a superfluid neutron star, where one fluid consists of the superfluid neutrons and the second fluid contains all the comoving constituents (protons, electrons). The two fluids are assumed to be ``free'' in the sense that vortex-mediated forces like mutual friction or pinning are absent, but they can be coupled by the equation of state, in particular by entrainment. The stationary background consists of the two fluids rotating uniformly around the same axis with potentially different rotation rates. We study the special cases of co-rotating backgrounds, vanishing entrainment, and the purely toroidal r-modes, analytically. We calculate numerically the eigenfunctions and frequencies of inertial modes in the general case of non co-rotating backgrounds, and study their dependence on the relat...
Magnetorotational instability in stratified, weakly ionised accretion discs
Salmeron, Roberto Aureliano; Salmeron, Raquel; Wardle, Mark
2003-01-01
We present a linear analysis of the vertical structure and growth of the magnetorotational instability in stratified, weakly ionised accretion discs, such as protostellar and quiescent dwarf novae systems. The method includes the effects of the magnetic coupling, the conductivity regime of the fluid and the strength of the magnetic field, which is initially vertical. The conductivity is treated as a tensor and assumed constant with height. We obtained solutions for the structure and growth rate of global unstable modes for different conductivity regimes, strengths of the initial magnetic field and coupling between ionised and neutral components of the fluid. The envelopes of short-wavelenght perturbations are determined by the action of competing local growth rates at different heights, driven by the vertical stratification of the disc. Ambipolar diffusion perturbations peak consistently higher above the midplane than modes including Hall conductivity. For weak coupling, perturbations including the Hall effec...
Second order closure for stratified convection: bulk region and overshooting
Biferale, L; Sbragaglia, M; Scagliarini, A; Toschi, F; Tripiccione, R
2011-01-01
The parameterization of small-scale turbulent fluctuations in convective systems and in the presence of strong stratification is a key issue for many applied problems in oceanography, atmospheric science and planetology. In the presence of stratification, one needs to cope with bulk turbulent fluctuations and with inversion regions, where temperature, density -or both- develop highly non-linear mean profiles due to the interactions between the turbulent boundary layer and the unmixed -stable- flow above/below it. We present a second order closure able to cope simultaneously with both bulk and boundary layer regions, and we test it against high-resolution state-of-the-art 2D numerical simulations in a convective and stratified belt for values of the Rayleigh number, up to Ra = 10^9. Data are taken from a Rayleigh-Taylor system confined by the existence of an adiabatic gradient.
Oxygenation of Stratified Reservoir Using Air Bubble Plume
Schladow, S. G.
2006-12-01
Excess nutrients loading from urban area and watershed into lakes and reservoirs increases the content of organic matter, which, through decomposition, needs increased dissolve oxygen (DO). Many eutrophic reservoirs and lakes cannot meet the DO requirement during stratified season and suffers from the hypolimnetic anoxia. As a result, benthic sediment produces anoxic products such as methane, hydrogen sulphide, ammonia, iron, manganese, and phosphorus. In order to address the hypolimnetic anoxia, oxygen is artificially supplied into reservoir using an aeration system (i.e., bubbler). The most common result of lake/reservoir aeration is to destratify the reservoir so that the water body may completely mix under natural phenomena and remain well oxygenated throughout. Other advantages of destratification are: (1) allows warm- water fish to inhabit the entire reservoir, (2) suppress the nutrient release from sediment, and (3) decreases the algal growth by sending them to the darker zone. A one-dimensional reservoir-bubbler model is developed and applied to examine the effects of an aeration system on mixing and dissolved oxygen dynamics in the Upper Peirce Reservoir, Singapore. After introduction of the aeration system in the reservoir, it was found that the hypolimnetic DO increased significantly, and the concentration of algae, soluble manganese and iron substantially reduced. It is found that the reservoir-bubbler model predicts the mixing (temperature as mixing parameter) and dissolved oxygen concentration in the reservoir with acceptable accuracy. It is shown in terms of bubbler mechanical efficiency (i.e., operating cost) and total DO contribution from the aeration system into the reservoir that the selections of airflow rate per diffuser, air bubble radius, and total number of diffusers are important design criteria of a bubbler system. However, the overall bubbler design also depends on the reservoir size and stratified area of interest, ambient climate, and
Nonlinear gravity-wave interactions in stratified turbulence
Remmel, Mark; Sukhatme, Jai; Smith, Leslie M.
2014-04-01
To investigate the dynamics of gravity waves in stratified Boussinesq flows, a model is derived that consists of all three-gravity-wave-mode interactions (the GGG model), excluding interactions involving the vortical mode. The GGG model is a natural extension of weak turbulence theory that accounts for exact three-gravity-wave resonances. The model is examined numerically by means of random, large-scale, high-frequency forcing. An immediate observation is a robust growth of the so-called vertically sheared horizontal flow (VSHF). In addition, there is a forward transfer of energy and equilibration of the nonzero-frequency (sometimes called "fast") gravity-wave modes. These results show that gravity-wave-mode interactions by themselves are capable of systematic interscale energy transfer in a stratified fluid. Comparing numerical simulations of the GGG model and the full Boussinesq system, for the range of Froude numbers ( Fr) considered (0.05 ≤ Fr ≤ 1), in both systems the VSHF is hardest to resolve. When adequately resolved, VSHF growth is more vigorous in the GGG model. Furthermore, a VSHF is observed to form in milder stratification scenarios in the GGG model than the full Boussinesq system. Finally, fully three-dimensional nonzero-frequency gravity-wave modes equilibrate in both systems and their scaling with vertical wavenumber follows similar power-laws. The slopes of the power-laws obtained depend on Fr and approach -2 (from above) at Fr = 0.05, which is the strongest stratification that can be properly resolved with our computational resources.
Visualization periodic flows in a continuously stratified fluid.
Bardakov, R.; Vasiliev, A.
2012-04-01
To visualize the flow pattern of viscous continuously stratified fluid both experimental and computational methods were developed. Computational procedures were based on exact solutions of set of the fundamental equations. Solutions of the problems of flows producing by periodically oscillating disk (linear and torsion oscillations) were visualized with a high resolutions to distinguish small-scale the singular components on the background of strong internal waves. Numerical algorithm of visualization allows to represent both the scalar and vector fields, such as velocity, density, pressure, vorticity, stream function. The size of the source, buoyancy and oscillation frequency, kinematic viscosity of the medium effects were traced in 2D an 3D posing problems. Precision schlieren instrument was used to visualize the flow pattern produced by linear and torsion oscillations of strip and disk in a continuously stratified fluid. Uniform stratification was created by the continuous displacement method. The buoyancy period ranged from 7.5 to 14 s. In the experiments disks with diameters from 9 to 30 cm and a thickness of 1 mm to 10 mm were used. Different schlieren methods that are conventional vertical slit - Foucault knife, vertical slit - filament (Maksoutov's method) and horizontal slit - horizontal grating (natural "rainbow" schlieren method) help to produce supplementing flow patterns. Both internal wave beams and fine flow components were visualized in vicinity and far from the source. Intensity of high gradient envelopes increased proportionally the amplitude of the source. In domains of envelopes convergence isolated small scale vortices and extended mushroom like jets were formed. Experiments have shown that in the case of torsion oscillations pattern of currents is more complicated than in case of forced linear oscillations. Comparison with known theoretical model shows that nonlinear interactions between the regular and singular flow components must be taken
Geng, Huiping
2016-11-01
CEPC was proposed as an electron and positron collider ring with a circumference of 50-100 km to study the Higgs boson. Since the proposal was made, the lattice design for CEPC has been carried out and a preliminary conceptual design report has been written at the end of 2014. In this paper, we will describe the principles of pretzel scheme design, which is one of most important issues in CEPC lattice design. Then, we will show the modification of the lattice based on the lattice design shown in the Pre-CDR. The latest pretzel orbit design result will also be shown. The issues remained to be solved in the present design will be discussed and a brief summary will be given at the end.
Mo Isotopes Record Destabilization of a Stratified Ocean at the Precambrian-Cambrian Boundary
Wille, M.; Nägler, T. F.; Schröder, S.; Lehmann, B.; Kramers, J. D.
2007-12-01
Here we present Mo isotope signatures in black shales from two sample sets (Ara group, Oman and Yangtze Platform, China) which were deposited at and shortly after the Precambrian-Cambrian boundary (PC-C). At the first view, the overall Mo isotopic signatures (delta98/95Mo) of the Early Cambrian black shales is 1.2 permil below recent ocean water, similar to the signature found in Mesoproterozoic shales (Arnold et al. 2004), indicating a larger proportion of Mo sedimentation under strongly euxinic conditions compared to recent oceans. A chemically stratified ocean with sulfidic deep waters and modestly oxygenated surface waters as proposed by Canfield (1998) for the Paleoproterozoic and Mesoproterozoic ocean, and Jiang et al. (2007) reported Carbon isotope data from the Ediacaran Yangtze platform (635-542 Ma) to be consistent with long-term deep ocean anoxia/euxinia. A stratified ocean therefore provides a plausible scenario to explain our new PC-C Mo isotope data. On closer inspection, a transient Mo isotopic signal following immediately after the PC-C boundary in both sample sets indicates a short but intense global non-steady state situation. In particular, a short term, drastic decrease of the Mo ocean inventory to almost zero is required to reconcile the observed Mo isotope data. Combined with the extreme Mo enrichment, found in the Chinese sulfide marker bed at the PC-C boundary, this signal has to be explained with a non-uniformitarian Mo scavenging mechanism. We put forward the hypothesis of mixing of oxidized, i.e. Mo rich surface waters with upwelling euxinic bottom water masses of the stratified ocean, as H2S is the most efficient Mo scavenging reagent. This scenario not only explains the transient isotopic signal, it can also be responsible for the sudden extinction of the Ediacaran fauna by H2S poisoning. In contrast, mass extinction scenarios like bolide impact, flood basalt eruptions or methane release, do not provide a direct explanation for the
Lefeuve-Mesgouez, Gaëlle; Chiavassa, Guillaume; Lombard, Bruno
2012-01-01
Wave propagation in a stratified fluid / porous medium is studied here using analytical and numerical methods. The semi-analytical method is based on an exact stiffness matrix method coupled with a matrix conditioning procedure, preventing the occurrence of poorly conditioned numerical systems. Special attention is paid to calculating the Fourier integrals. The numerical method is based on a high order finite-difference time-domain scheme. Mesh refinement is applied near the interfaces to discretize the slow compressional diffusive wave predicted by Biot's theory. Lastly, an immersed interface method is used to discretize the boundary conditions. The numerical benchmarks are based on realistic soil parameters and on various degrees of hydraulic contact at the fluid / porous boundary. The time evolution of the acoustic pressure and the porous velocity is plotted in the case of one and four interfaces. The excellent level of agreement found to exist between the two approaches confirms the validity of both metho...
Extent of atypical hyperplasia stratifies breast cancer risk in 2 independent cohorts of women.
Degnim, Amy C; Dupont, William D; Radisky, Derek C; Vierkant, Robert A; Frank, Ryan D; Frost, Marlene H; Winham, Stacey J; Sanders, Melinda E; Smith, Jeffrey R; Page, David L; Hoskin, Tanya L; Vachon, Celine M; Ghosh, Karthik; Hieken, Tina J; Denison, Lori A; Carter, Jodi M; Hartmann, Lynn C; Visscher, Daniel W
2016-10-01
Women with atypical hyperplasia (AH) on breast biopsy have a substantially increased risk of breast cancer (BC). Here the BC risk for the extent and subtype of AH is reported for 2 separate cohorts. All samples containing AH were included from 2 cohorts of women with benign breast disease (Mayo Clinic and Nashville). Histology review quantified the number of foci of atypical ductal hyperplasia (ADH) and atypical lobular hyperplasia (ALH). The BC risk was stratified for the number of AH foci within AH subtypes. The study included 708 Mayo AH subjects and 466 Nashville AH subjects. In the Mayo cohort, an increasing number of foci of AH was associated with a significant increase in the risk of BC both for ADH (relative risks of 2.61, 5.21, and 6.36 for 1, 2, and ≥3 foci, respectively; P for linear trend = .006) and for ALH (relative risks of 2.56, 3.50, and 6.79 for 1, 2, and ≥3 foci, respectively; P for linear trend = .001). In the Nashville cohort, the relative risks of BC for ADH were 2.70, 5.17, and 15.06 for 1, 2, and ≥3 foci, respectively (P for linear trend < .001); for ALH, the relative risks also increased but not significantly (2.61, 3.48, and 4.02, respectively; P = .148). When the Mayo and Nashville samples were combined, the risk increased significantly for 1, 2, and ≥3 foci: the relative risks were 2.65, 5.19, and 8.94, respectively, for ADH (P < .001) and 2.58, 3.49, and 4.97, respectively, for ALH (P = .001). In 2 independent cohort studies of benign breast disease, the extent of atypia stratified the long-term BC risk for ADH and ALH. Cancer 2016;122:2971-2978. © 2016 American Cancer Society. © 2016 American Cancer Society.
Deep silicon maxima in the stratified oligotrophic Mediterranean Sea
Y. Crombet
2011-02-01
Full Text Available The silicon biogeochemical cycle has been studied in the Mediterranean Sea during late summer/early autumn 1999 and summer 2008. The distribution of nutrients, particulate carbon and silicon, fucoxanthin (Fuco, and total chlorophyll-a (TChl-a were investigated along an eastward gradient of oligotrophy during two cruises (PROSOPE and BOUM encompassing the entire Mediterranean Sea during the stratified period. At both seasons, surface waters were depleted in nutrients and the nutriclines gradually deepened towards the East, the phosphacline being the deepest in the easternmost Levantine basin. Following the nutriclines, parallel deep maxima of biogenic silica (DSM, fucoxanthin (DFM and TChl-a (DCM were evidenced during both seasons with maximal concentrations of 0.45 μmol L^{−1} for BSi, 0.26 μg L^{−1} for Fuco, and 1.70 μg L^{−1} for TChl-a, all measured during summer. Contrary to the DCM which was a persistent feature in the Mediterranean Sea, the DSM and DFMs were observed in discrete areas of the Alboran Sea, the Algero-Provencal basin, the Ionian sea and the Levantine basin, indicating that diatoms were able to grow at depth and dominate the DCM under specific conditions. Diatom assemblages were dominated by Chaetoceros spp., Leptocylindrus spp., Pseudonitzschia spp. and the association between large centric diatoms (Hemiaulus hauckii and Rhizosolenia styliformis and the cyanobacterium Richelia intracellularis was observed at nearly all sites. The diatom's ability to grow at depth is commonly observed in other oligotrophic regions and could play a major role in ecosystem productivity and carbon export to depth. Contrary to the common view that Si and siliceous phytoplankton are not major components of the Mediterranean biogeochemistry, we suggest here that diatoms, by persisting at depth during the stratified period, could contribute to a
Fishing and the oceanography of a stratified shelf sea
Sharples, Jonathan; Ellis, Jim R.; Nolan, Glenn; Scott, Beth E.
2013-10-01
Fishing vessel position data from the Vessel Monitoring System (VMS) were used to investigate fishing activity in the Celtic Sea, a seasonally-stratifying, temperate region on the shelf of northwest Europe. The spatial pattern of fishing showed that three main areas are targeted: (1) the Celtic Deep (an area of deeper water with fine sediments), (2) the shelf edge, and (3) an area covering several large seabed banks in the central Celtic Sea. Data from each of these regions were analysed to examine the contrasting seasonality of fishing activity, and to highlight where the spring-neap tidal cycle appears to be important to fishing. The oceanographic characteristics of the Celtic Sea were considered alongside the distribution and timing of fishing, illustrating likely contrasts in the underlying environmental drivers of the different fished regions. In the central Celtic Sea, fishing mainly occurred during the stratified period between April and August. Based on evidence provided in other papers of this Special Issue, we suggest that the fishing in this area is supported by (1) a broad increase in primary production caused by lee-waves generated by seabed banks around spring tides driving large supplies of nutrients into the photic zone, and (2) greater concentrations of zooplankton within the region influenced by the seabed banks and elevated primary production. In contrast, while the shelf edge is a site of elevated surface chlorophyll, previous work has suggested that the periodic mixing generated by an internal tide at the shelf edge alters the size-structure of the phytoplankton community which fish larvae from the spawning stocks along the shelf edge are able to exploit. The fishery for Nephrops norvegicus in the Celtic Deep was the only one to show a significant spring-neap cycle, possibly linked to Nephrops foraging outside their burrows less during spring tides. More tentatively, the fishery for Nephrops correlated most strongly with a localised shift in
Improved Ternary Subdivision Interpolation Scheme
WANG Huawei; QIN Kaihuai
2005-01-01
An improved ternary subdivision interpolation scheme was developed for computer graphics applications that can manipulate open control polygons unlike the previous ternary scheme, with the resulting curve proved to be still C2-continuous. Parameterizations of the limit curve near the two endpoints are given with expressions for the boundary derivatives. The split joint problem is handled with the interpolating ternary subdivision scheme. The improved scheme can be used for modeling interpolation curves in computer aided geometric design systems, and provides a method for joining two limit curves of interpolating ternary subdivisions.
Formal Verification of NTRUEncrypt Scheme
Gholam Reza Moghissi
2016-04-01
Full Text Available In this paper we explore a mechanized verification of the NTRUEncrypt scheme, with the formal proof system Isabelle/HOL. More precisely, the functional correctness of this algorithm, in its reduced form, is formally verified with computer support. We show that this scheme is correct what is a necessary condition for the usefulness of any cryptographic encryption scheme. Besides, we present a convenient and application specific formalization of the NTRUEncrypt scheme in the Isabelle/HOL system that can be used in further study around the functional and security analysis of NTRUEncrypt family.
AUTISTIC CHILDREN PROTECTION SCHEME
Dragan LUKIC
1998-09-01
Full Text Available The present article sets forth the theoretical grounds which make the basis for the organizational scheme of the autistic persons social protection. This protection consists of the below listed forms of work:· Health service with the role of an early detection and participation in the creation of rehabilitation programs;· Social protection with its programs of work from the diagnostics where the defectologist makes a team together with the physician and the psychologists to the systems of rehabilitation institutions where the defectologist’s is the main responsibility.The present article underlines two facts, namely:· that an autistic person requires to be followed and every spare moment used to promote and advance the activities the doer commenced himself instead of having him carry out the programs which are beyond his internal motivations and which he finds emotionally inaccessible;· that and form of work organization with autistic persons must subordinate its administrative part to the basic professional requirements this kind of disorder (handicap sets in front of each professional.
Robust risk prediction with biomarkers under two-phase stratified cohort design.
Payne, Rebecca; Yang, Ming; Zheng, Yingye; Jensen, Majken K; Cai, Tianxi
2016-12-01
Identification of novel biomarkers for risk prediction is important for disease prevention and optimal treatment selection. However, studies aiming to discover which biomarkers are useful for risk prediction often require the use of stored biological samples from large assembled cohorts, and thus the depletion of a finite and precious resource. To make efficient use of such stored samples, two-phase sampling designs are often adopted as resource-efficient sampling strategies, especially when the outcome of interest is rare. Existing methods for analyzing data from two-phase studies focus primarily on single marker analysis or fitting the Cox regression model to combine information from multiple markers. However, the Cox model may not fit the data well. Under model misspecification, the composite score derived from the Cox model may not perform well in predicting the outcome. Under a general two-phase stratified cohort sampling design, we present a novel approach to combining multiple markers to optimize prediction by fitting a flexible nonparametric transformation model. Using inverse probability weighting to account for the outcome-dependent sampling, we propose to estimate the model parameters by maximizing an objective function which can be interpreted as a weighted C-statistic for survival outcomes. Regardless of model adequacy, the proposed procedure yields a sensible composite risk score for prediction. A major obstacle for making inference under two phase studies is due to the correlation induced by the finite population sampling, which prevents standard inference procedures such as the bootstrap from being used for variance estimation. We propose a resampling procedure to derive valid confidence intervals for the model parameters and the C-statistic accuracy measure. We illustrate the new methods with simulation studies and an analysis of a two-phase study of high-density lipoprotein cholesterol (HDL-C) subtypes for predicting the risk of coronary heart
Turbulence comes in bursts in stably stratified flows
Rorai, C; Pouquet, A
2013-01-01
There is a clear distinction between simple laminar and complex turbulent fluids. But in some cases, as for the nocturnal planetary boundary layer, a stable and well-ordered flow can develop intense and sporadic bursts of turbulent activity which disappear slowly in time. This phenomenon is ill-understood and poorly modeled; and yet, it is central to our understanding of weather and climate dynamics. We present here a simple model which shows that in stably stratified turbulence, the stronger bursts can occur when the flow is expected to be more stable. The bursts are generated by a rapid non-linear amplification of energy stored in waves, and are associated with energetic interchanges between vertical velocity and temperature (or density) fluctuations. Direct numerical simulations on grids of 2048^3 points confirm this somewhat paradoxical result of measurably stronger events for more stable flows, displayed not only in the temperature and vertical velocity derivatives, but also in the amplitude of the field...
DNS of stratified spatially-developing turbulent thermal boundary layers
Araya, Guillermo; Castillo, Luciano; Jansen, Kenneth
2012-11-01
Direct numerical simulations (DNS) of spatially-developing turbulent thermal boundary layers under stratification are performed. It is well known that the transport phenomena of the flow is significantly affected by buoyancy, particularly in urban environments where stable and unstable atmospheric boundary layers are encountered. In the present investigation, the Dynamic Multi-scale approach by Araya et al. (JFM, 670, 2011) for turbulent inflow generation is extended to thermally stratified boundary layers. Furthermore, the proposed Dynamic Multi-scale approach is based on the original rescaling-recycling method by Lund et al. (1998). The two major improvements are: (i) the utilization of two different scaling laws in the inner and outer parts of the boundary layer to better absorb external conditions such as inlet Reynolds numbers, streamwise pressure gradients, buoyancy effects, etc., (ii) the implementation of a Dynamic approach to compute scaling parameters from the flow solution without the need of empirical correlations as in Lund et al. (1998). Numerical results are shown for ZPG flows at high momentum thickness Reynolds numbers (~ 3,000) and a comparison with experimental data is also carried out.
Stratified patterns of divorce: Earnings, education, and gender
Amit Kaplan
2015-05-01
Full Text Available Background: Despite evidence that divorce has become more prevalent among weaker socioeconomic groups, knowledge about the stratification aspects of divorce in Israel is lacking. Moreover, although scholarly debate recognizes the importance of stratificational positions with respect to divorce, less attention has been given to the interactions between them. Objective: Our aim is to examine the relationship between social inequality and divorce, focusing on how household income, education, employment stability, relative earnings, and the intersection between them affect the risk of divorce in Israel. Methods: The data is derived from combined census files for 1995-2008, annual administrative employment records from the National Insurance Institute and the Tax Authority, and data from the Civil Registry of Divorce. We used a series of discrete-time event-history analysis models for marital dissolution. Results: Couples in lower socioeconomic positions had a higher risk of divorce in Israel. Higher education in general, and homogamy in terms of higher education (both spouses have degrees in particular, decreased the risk of divorce. The wife's relative earnings had a differential effect on the likelihood of divorce, depending on household income: a wife who outearned her husband increased the log odds of divorce more in the upper tertiles than in the lower tertile. Conclusions: Our study shows that divorce indeed has a stratified pattern and that weaker socioeconomic groups experience the highest levels of divorce. Gender inequality within couples intersects with the household's economic and educational resources.
Self-Knowledge and Risk in Stratified Medicine.
Hordern, Joshua
2017-04-01
This article considers why and how self-knowledge is important to communication about risk and behaviour change by arguing for four claims. First, it is doubtful that genetic knowledge should properly be called 'self-knowledge' when its ordinary effects on self-motivation and behaviour change seem so slight. Second, temptations towards a reductionist, fatalist, construal of persons' futures through a 'molecular optic' should be resisted. Third, any plausible effort to change people's behaviour must engage with cultural self-knowledge, values and beliefs, catalysed by the communication of genetic risk. For example, while a Judaeo-Christian notion of self-knowledge is distinctively theological, people's self-knowledge is plural in its insight and sources. Fourth, self-knowledge is found in compassionate, if tense, communion which yields freedom from determinism even amidst suffering. Stratified medicine thus offers a newly precise kind of humanising health care through societal solidarity with the riskiest. However, stratification may also mean that molecularly unstratified, 'B' patients' experience involves accentuated suffering and disappointment, a concern requiring further research.
Stratified Flow Past a Hill: Dividing Streamline Concept Revisited
Leo, Laura S.; Thompson, Michael Y.; Di Sabatino, Silvana; Fernando, Harindra J. S.
2016-06-01
The Sheppard formula (Q J R Meteorol Soc 82:528-529, 1956) for the dividing streamline height H_s assumes a uniform velocity U_∞ and a constant buoyancy frequency N for the approach flow towards a mountain of height h, and takes the form H_s/h=( {1-F} ) , where F=U_{∞}/Nh. We extend this solution to a logarithmic approach-velocity profile with constant N. An analytical solution is obtained for H_s/h in terms of Lambert-W functions, which also suggests alternative scaling for H_s/h. A `modified' logarithmic velocity profile is proposed for stably stratified atmospheric boundary-layer flows. A field experiment designed to observe H_s is described, which utilized instrumentation from the spring field campaign of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program. Multiple releases of smoke at F≈ 0.3-0.4 support the new formulation, notwithstanding the limited success of experiments due to logistical constraints. No dividing streamline is discerned for F≈ 10, since, if present, it is too close to the foothill. Flow separation and vortex shedding is observed in this case. The proposed modified logarithmic profile is in reasonable agreement with experimental observations.
Large eddy simulation of unsteady lean stratified premixed combustion
Duwig, C. [Division of Fluid Mechanics, Department of Energy Sciences, Lund University, SE 221 00 Lund (Sweden); Fureby, C. [Division of Weapons and Protection, Warheads and Propulsion, The Swedish Defense Research Agency, FOI, SE 147 25 Tumba (Sweden)
2007-10-15
Premixed turbulent flame-based technologies are rapidly growing in importance, with applications to modern clean combustion devices for both power generation and aeropropulsion. However, the gain in decreasing harmful emissions might be canceled by rising combustion instabilities. Unwanted unsteady flame phenomena that might even destroy the whole device have been widely reported and are subject to intensive studies. In the present paper, we use unsteady numerical tools for simulating an unsteady and well-documented flame. Computations were performed for nonreacting, perfectly premixed and stratified premixed cases using two different numerical codes and different large-eddy-simulation-based flamelet models. Nonreacting simulations are shown to agree well with experimental data, with the LES results capturing the mean features (symmetry breaking) as well as the fluctuation level of the turbulent flow. For reacting cases, the uncertainty induced by the time-averaging technique limited the comparisons. Given an estimate of the uncertainty, the numerical results were found to reproduce well the experimental data in terms both of mean flow field and of fluctuation levels. In addition, it was found that despite relying on different assumptions/simplifications, both numerical tools lead to similar predictions, giving confidence in the results. Moreover, we studied the flame dynamics and particularly the response to a periodic pulsation. We found that above a certain excitation level, the flame dynamic changes and becomes rather insensitive to the excitation/instability amplitude. Conclusions regarding the self-growth of thermoacoustic waves were drawn. (author)
Economic evaluation in stratified medicine: methodological issues and challenges
Hans-Joerg eFugel
2016-05-01
Full Text Available Background: Stratified Medicine (SM is becoming a practical reality with the targeting of medicines by using a biomarker or genetic-based diagnostic to identify the eligible patient sub-population. Like any healthcare intervention, SM interventions have costs and consequences that must be considered by reimbursement authorities with limited resources. Methodological standards and guidelines exist for economic evaluations in clinical pharmacology and are an important component for health technology assessments (HTAs in many countries. However, these guidelines have initially been developed for traditional pharmaceuticals and not for complex interventions with multiple components. This raises the issue as to whether these guidelines are adequate to SM interventions or whether new specific guidance and methodology is needed to avoid inconsistencies and contradictory findings when assessing economic value in SM.Objective: This article describes specific methodological challenges when conducting health economic (HE evaluations for SM interventions and outlines potential modifications necessary to existing evaluation guidelines /principles that would promote consistent economic evaluations for SM.Results/Conclusions: Specific methodological aspects for SM comprise considerations on the choice of comparator, measuring effectiveness and outcomes, appropriate modelling structure and the scope of sensitivity analyses. Although current HE methodology can be applied for SM, greater complexity requires further methodology development and modifications in the guidelines.
BIPOLAR MAGNETIC SPOTS FROM DYNAMOS IN STRATIFIED SPHERICAL SHELL TURBULENCE
Jabbari, Sarah; Brandenburg, Axel; Kleeorin, Nathan; Mitra, Dhrubaditya; Rogachevskii, Igor, E-mail: sarahjab@kth.se [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)
2015-06-01
Recent work by Mitra et al. (2014) has shown that in strongly stratified forced two-layer turbulence with helicity and corresponding large-scale dynamo action in the lower layer, and nonhelical turbulence in the upper, a magnetic field occurs in the upper layer in the form of sharply bounded bipolar magnetic spots. Here we extend this model to spherical wedge geometry covering the northern hemisphere up to 75° latitude and an azimuthal extent of 180°. The kinetic helicity and therefore also the large-scale magnetic field are strongest at low latitudes. For moderately strong stratification, several bipolar spots form that eventually fill the full longitudinal extent. At early times, the polarity of spots reflects the orientation of the underlying azimuthal field, as expected from Parker’s Ω-shaped flux loops. At late times their tilt changes such that there is a radial field of opposite orientation at different latitudes separated by about 10°. Our model demonstrates the spontaneous formation of spots of sizes much larger than the pressure scale height. Their tendency to produce filling factors close to unity is argued to be reminiscent of highly active stars. We confirm that strong stratification and strong scale separation are essential ingredients behind magnetic spot formation, which appears to be associated with downflows at larger depths.
Local properties of countercurrent stratified steam-water flow
Kim, H J
1985-10-01
A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel/flat plate geometry over a wide range of inclination angles (4/sup 0/-87/sup 0/) at several aspect ratios. Variables were inlet water and steam flow rates, and inlet water temperature. Local condensation rates and pressure gradients were measured, and local condensation heat transfer coefficients and interfacial shear stress were calculated. Contact probe traverses of the surface waves were made, which allowed a statistical analysis of the wave properties. The local condensation Nusselt number was correlated in terms of local water and steam Reynolds or Froude numbers, as well as the liquid Prandtl number. A turbulence-centered model developed by Theofanous, et al. principally for gas absorption in several geometries, was modified. A correlation for the interfacial shear stress and the pressure gradient agreed with measured values. Mean water layer thicknesses were calculated. Interfacial wave parameters, such as the mean water layer thickness, liquid fraction probability distribution, wave amplitude and wave frequency, are analyzed.
Numerical Study of Stratified Charge Combustion in Wave Rotors
Nalim, M. Razi
1997-01-01
A wave rotor may be used as a pressure-gain combustor effecting non-steady flow, and intermittent, confined combustion to enhance gas turbine engine performance. It will be more compact and probably lighter than an equivalent pressure-exchange wave rotor, yet will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel/air ratio to sub-flammable values, premixed stratification techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperature well below autoignition conditions. One-dimensional, unsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a flammability limit temperature. For good combustion efficiency, a stratification strategy is developed which concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature profiles and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak local gas temperatures will result in excessive temperatures within the rotor housing unless additional cooling methods are used. The rotor itself will have acceptable temperatures, but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct-rotor interaction.
Stratifying the Risk of Venous Thromboembolism in Otolaryngology
Shuman, Andrew G.; Hu, Hsou Mei; Pannucci, Christopher J.; Jackson, Christopher R.; Bradford, Carol R.; Bahl, Vinita
2015-01-01
Objective The consequences of perioperative venous thromboembolism (VTE) are devastating; identifying patients at risk is an essential step in reducing morbidity and mortality. The utility of perioperative VTE risk assessment in otolaryngology is unknown. This study was designed to risk-stratify a diverse population of otolaryngology patients for VTE events. Study Design Retrospective cohort study. Setting Single-institution academic tertiary care medical center. Subjects and Methods Adult patients presenting for otolaryngologic surgery requiring hospital admission from 2003 to 2010 who did not receive VTE chemoprophylaxis were included. The Caprini risk assessment was retrospectively scored via a validated method of electronic chart abstraction. Primary study variables were Caprini risk scores and the incidence of perioperative venous thromboembolic outcomes. Results A total of 2016 patients were identified. The overall 30-day rate of VTE was 1.3%. The incidence of VTE in patients with a Caprini risk score of 6 or less was 0.5%. For patients with scores of 7 or 8, the incidence was 2.4%. Patients with a Caprini risk score greater than 8 had an 18.3% incidence of VTE and were significantly more likely to develop a VTE when compared to patients with a Caprini risk score less than 8 (P otolaryngology patients for 30-day VTE events and allows otolaryngologists to identify patient subgroups who have a higher risk of VTE in the absence of chemoprophylaxis. PMID:22261490
Mixing efficiency of turbulent patches in stably stratified flows
Garanaik, Amrapalli; Venayagamoorthy, Subhas Karan
2016-11-01
A key quantity that is essential for estimating the turbulent diapycnal (irreversible) mixing in stably stratified flow is the mixing efficiency Rf*, which is a measure of the amount of turbulent kinetic energy that is irreversibly converted into background potential energy. In particular, there is an ongoing debate in the oceanographic mixing community regarding the utility of the buoyancy Reynolds number (Reb) , particularly with regard to how mixing efficiency and diapycnal diffusivity vary with Reb . Specifically, is there a universal relationship between the intensity of turbulence and the strength of the stratification that supports an unambiguous description of mixing efficiency based on Reb ? The focus of the present study is to investigate the variability of Rf* by considering oceanic turbulence data obtained from microstructure profiles in conjunction with data from laboratory experiments and DNS. Field data analysis has done by identifying turbulent patches using Thorpe sorting method for potential density. The analysis clearly shows that high mixing efficiencies can persist at high buoyancy Reynolds numbers. This is contradiction to previous studies which predict that mixing efficiency should decrease universally for Reb greater than O (100) . Funded by NSF and ONR.
Simulation and study of stratified flows around finite bodies
Gushchin, V. A.; Matyushin, P. V.
2016-06-01
The flows past a sphere and a square cylinder of diameter d moving horizontally at the velocity U in a linearly density-stratified viscous incompressible fluid are studied. The flows are described by the Navier-Stokes equations in the Boussinesq approximation. Variations in the spatial vortex structure of the flows are analyzed in detail in a wide range of dimensionless parameters (such as the Reynolds number Re = Ud/ ν and the internal Froude number Fr = U/( Nd), where ν is the kinematic viscosity and N is the buoyancy frequency) by applying mathematical simulation (on supercomputers of Joint Supercomputer Center of the Russian Academy of Sciences) and three-dimensional flow visualization. At 0.005 < Fr < 100, the classification of flow regimes for the sphere (for 1 < Re < 500) and for the cylinder (for 1 < Re < 200) is improved. At Fr = 0 (i.e., at U = 0), the problem of diffusion-induced flow past a sphere leading to the formation of horizontal density layers near the sphere's upper and lower poles is considered. At Fr = 0.1 and Re = 50, the formation of a steady flow past a square cylinder with wavy hanging density layers in the wake is studied in detail.
Towards Cost-efficient Sampling Methods
Peng, Luo; Yongli, Li; Chong, Wu
2014-01-01
The sampling method has been paid much attention in the field of complex network in general and statistical physics in particular. This paper presents two new sampling methods based on the perspective that a small part of vertices with high node degree can possess the most structure information of a network. The two proposed sampling methods are efficient in sampling the nodes with high degree. The first new sampling method is improved on the basis of the stratified random sampling method and...
Walton, Karl; Blunt, Liam; Fleming, Leigh
2015-09-01
Mass finishing is amongst the most widely used finishing processes in modern manufacturing, in applications from deburring to edge radiusing and polishing. Processing objectives are varied, ranging from the cosmetic to the functionally critical. One such critical application is the hydraulically smooth polishing of aero engine component gas-washed surfaces. In this, and many other applications the drive to improve process control and finish tolerance is ever present. Considering its widespread use mass finishing has seen limited research activity, particularly with respect to surface characterization. The objectives of the current paper are to; characterise the mass finished stratified surface and its development process using areal surface parameters, provide guidance on the optimal parameters and sampling method to characterise this surface type for a given application, and detail the spatial variation in surface topography due to coupon edge shadowing. Blasted and peened square plate coupons in titanium alloy are wet (vibro) mass finished iteratively with increasing duration. Measurement fields are precisely relocated between iterations by fixturing and an image superimposition alignment technique. Surface topography development is detailed with ‘log of process duration’ plots of the ‘areal parameters for scale-limited stratified functional surfaces’, (the Sk family). Characteristic features of the Smr2 plot are seen to map out the processing of peak, core and dale regions in turn. These surface process regions also become apparent in the ‘log of process duration’ plot for Sq, where lower core and dale regions are well modelled by logarithmic functions. Surface finish (Ra or Sa) with mass finishing duration is currently predicted with an exponential model. This model is shown to be limited for the current surface type at a critical range of surface finishes. Statistical analysis provides a group of areal parameters including; Vvc, Sq, and Sdq
Chaotic communication scheme with multiplication
Bobreshov, A. M.; Karavaev, A. A.
2007-05-01
A new scheme of data transmission with nonlinear admixing is described, in which the two mutually inverse operations (multiplication and division) ensure multiplicative mixing of the informative and chaotic signals that provides a potentially higher degree of security. A special feature of the proposed scheme is the absence of limitations (related to the division by zero) imposed on the types of informative signals.
Homographic scheme for Riccati equation
Dubois, François
2011-01-01
In this paper we present a numerical scheme for the resolution of matrix Riccati equation, usualy used in control problems. The scheme is unconditionnaly stable and the solution is definite positive at each time step of the resolution. We prove the convergence in the scalar case and present several numerical experiments for classical test cases.
Differential operators and automorphism schemes
无
2010-01-01
The ring of global differential operators of a variety is in closed and deep relation with its automorphism scheme.This relation can be applied to the study of homogeneous schemes,giving some criteria of homogeneity,a generalization of Serre-Lang theorem,and some consequences about abelian varieties.
Jerzy Czerski
2014-02-01
Full Text Available The germination of whole seeds, the seeds without coat and isolated embryos of apple cv. "Antonówka Zwykła" after 90 days of cold-stratification was compared with the germination of embryos isolated from non-stratified seeds. They were germinated under 16hrs during a day at temperature 25°C and 20°C during the night. It has been found that after 2 weeks whole stratified seeds germinated in 5 per cent, seeds without coat in 25 per cent and isolated embryos in 98 per cent. Isolated embryos from nun-stratified seeds, after 2 weeks, germinated in the range from 75 to 88 per cent. The results indicate the similar germination ability of embryos isolated from nun-stratified seeds. The seedling populations obtained from embryo's stratified and non-stratified seeds were fully comparable and they evaluated: 1 a wide range of individual differences within population, 2 a similar number of seedlings in each class of shoot length, 3 a similar morphological habitus in each class of shoot length, 4 a similar fresh leaf weight and whole plant increment.
McCune, Lorraine; Vihman, Marilyn May
A study examined the consistency of consonant use in the infant's transition period from babbling to early words. Phonetic data were collected from the speech of 10 infants aged 9 to 15 months. Analysis of consonant distribution patterns indicate striking segmental preferences in all 10 children, with some segments more prominent for the sample as…
STUDIES OF TWO-PHASE PLUMES IN STRATIFIED ENVIRONMENTS
Scott A. Socolofsky; Brian C. Crounse; E. Eric Adams
1998-11-18
Two-phase plumes play an important role in the more practical scenarios for ocean sequestration of CO{sub 2}--i.e. dispersing CO{sub 2} as a buoyant liquid from either a bottom-mounted or ship-towed pipeline. Despite much research on related applications, such as for reservoir destratification using bubble plumes, our understanding of these flows is incomplete, especially concerning the phenomenon of plume peeling in a stratified ambient. To address this deficiency, we have built a laboratory facility in which we can make fundamental measurements of plume behavior. Although we are using air, oil and sediments as our sources of buoyancy (rather than CO{sub 2}), by using models, our results can be directly applied to field scale CO{sub 2} releases to help us design better CO{sub 2} injection systems, as well as plan and interpret the results of our up-coming international field experiment. The experimental facility designed to study two-phase plume behavior similar to that of an ocean CO{sub 2} release includes the following components: 1.22 x 1.22 x 2.44 m tall glass walled tank; Tanks and piping for the two-tank stratification method for producing step- and linearly-stratified ambient conditions; Density profiling system using a conductivity and temperature probe mounted to an automated depth profiler; Lighting systems, including a virtual point source light for shadowgraphs and a 6 W argon-ion laser for laser induced fluorescence (LIF) imaging; Imaging system, including a digital, progressive scanning CCD camera, computerized framegrabber, and image acquisition and analysis software; Buoyancy source diffusers having four different air diffusers, two oil diffusers, and a planned sediment diffuser; Dye injection method using a Mariotte bottle and a collar diffuser; and Systems integration software using the Labview graphical programming language and Windows NT. In comparison with previously reported experiments, this system allows us to extend the parameter range of
A model for evaluating the ballistic resistance of stratified packs
Pirvu, C.; Georgescu, C.; Badea, S.; Deleanu, L.
2016-08-01
Models for evaluating the ballistic performance of stratified packs are useful in reducing the time for laboratory tests, understanding the failure process and identifying key factors to improve the architecture of the packs. The authors present the results of simulating the bullet impact on a packs made of 24 layers, taking into consideration the friction between layers (μ = 0.4) and the friction between bullet and layers (μ = 0.3). The aim of this study is to obtain a number of layers that allows for the bullet arrest in the packs and to have several layers undamaged in order to offer a high level of safety for this kind of packs that could be included in individual armors. The model takes into account the yield and fracture limits of the two materials the bullet is made of and those for one layer, here considered as an orthotropic material, having maximum equivalent plastic strain of 0.06. All materials are considered to have bilinear isotropic hardening behavior. After documentation, the model was designed as isothermal because thermal influence of the impact is considered low for these impact velocities. The model was developed with the help of Ansys 14.5. Each layer has 200 mm × 200 × 0.35 mm. The bullet velocity just before impact was 400 m/s, a velocity characterizing the average values obtained in close range with a ballistic barrel and the bullet model is following the shape and dimensions of the 9 mm FMJ (full metal jacket). The model and the results concerning the number of broken layers were validated by experiments, as the number of broken layers for the actual pack (made of 24 layers of LFT SB1) were also seven...eight. The models for ballistic impact are useful when they are particularly formulated for resembling to the actual system projectile - target.
Internal and vorticity waves in decaying stratified flows
Matulka, A.; Cano, D.
2009-04-01
Most predictive models fail when forcing at the Rossby deformation Radius is important and a large range of scales have to be taken into account. When mixing of reactants or pollutants has to be accounted, the range of scales spans from hundreds of Kilometers to the Bachelor or Kolmogorov sub milimiter scales. We present some theoretical arguments to describe the flow in terms of the three dimensional vorticity equations, using a lengthscale related to the vorticity (or enstrophy ) transport. Effect of intermittent eddies and non-homogeneity of diffusion are also key issues in the environment because both stratification and rotation body forces are important and cause anisotropy/non-homogeneity. These problems need further theoretical, numerical and observational work and one approach is to try to maximize the relevant geometrical information in order to understand and therefore predict these complex environmental dispersive flows. The importance of the study of turbulence structure and its relevance in diffusion of contaminants in environmental flows is clear when we see the effect of environmental disasters such as the Prestige oil spill or the Chernobil radioactive cloud spread in the atmosphere. A series of Experiments have been performed on a strongly stratified two layer fluid consisting of Brine in the bottom and freshwater above in a 1 square meter tank. The evolution of the vortices after the passage of a grid is video recorded and Particle tracking is applied on small pliolite particles floating at the interface. The combination of internal waves and vertical vorticity produces two separate time scales that may produce resonances. The vorticity is seen to oscilate in a complex way, where the frecuency decreases with time.
The nonlinear evolution of modes on unstable stratified shear layers
Blackaby, Nicholas; Dando, Andrew; Hall, Philip
1993-06-01
The nonlinear development of disturbances in stratified shear flows (having a local Richardson number of value less than one quarter) is considered. Such modes are initially fast growing but, like related studies, we assume that the viscous, non-parallel spreading of the shear layer results in them evolving in a linear fashion until they reach a position where their amplitudes are large enough and their growth rates have diminished sufficiently so that amplitude equations can be derived using weakly nonlinear and non-equilibrium critical-layer theories. Four different basic integro-differential amplitude equations are possible, including one due to a novel mechanism; the relevant choice of amplitude equation, at a particular instance, being dependent on the relative sizes of the disturbance amplitude, the growth rate of the disturbance, its wavenumber, and the viscosity of the fluid. This richness of choice of possible nonlinearities arises mathematically from the indicial Frobenius roots of the governing linear inviscid equation (the Taylor-Goldstein equation) not, in general, differing by an integer. The initial nonlinear evolution of a mode will be governed by an integro-differential amplitude equations with a cubic nonlinearity but the resulting significant increase in the size of the disturbance's amplitude leads on to the next stage of the evolution process where the evolution of the mode is governed by an integro-differential amplitude equations with a quintic nonlinearity. Continued growth of the disturbance amplitude is expected during this stage, resulting in the effects of nonlinearity spreading to outside the critical level, by which time the flow has become fully nonlinear.
Interfacial instabilities in a stratified flow of two superposed fluids
Schaflinger, Uwe
1994-06-01
Here we shall present a linear stability analysis of a laminar, stratified flow of two superposed fluids which are a clear liquid and a suspension of solid particles. The investigation is based upon the assumption that the concentration remains constant within the suspension layer. Even for moderate flow-rates the base-state results for a shear induced resuspension flow justify the latter assumption. The numerical solutions display the existence of two different branches that contribute to convective instability: long and short waves which coexist in a certain range of parameters. Also, a range exists where the flow is absolutely unstable. That means a convectively unstable resuspension flow can be only observed for Reynolds numbers larger than a lower, critical Reynolds number but still smaller than a second critical Reynolds number. For flow rates which give rise to a Reynolds number larger than the second critical Reynolds number, the flow is absolutely unstable. In some cases, however, there exists a third bound beyond that the flow is convectively unstable again. Experiments show the same phenomena: for small flow-rates short waves were usually observed but occasionally also the coexistence of short and long waves. These findings are qualitatively in good agreement with the linear stability analysis. Larger flow-rates in the range of the second critical Reynolds number yield strong interfacial waves with wave breaking and detached particles. In this range, the measured flow-parameters, like the resuspension height and the pressure drop are far beyond the theoretical results. Evidently, a further increase of the Reynolds number indicates the transition to a less wavy interface. Finally, the linear stability analysis also predicts interfacial waves in the case of relatively small suspension heights. These results are in accordance with measurements for ripple-type instabilities as they occur under laminar and viscous conditions for a mono-layer of particles.
Magnetoacoustic Waves in Stratified Atmospheres with a Magnetic Null Point
Tarr, Lucas A.; Linton, Mark; Leake, James E.
2016-05-01
Magnetic fields strongly modify the propagation of MHD waves from the photosphere to the low corona, as can be shown exactly for the most simple case of a uniform magnetic field and isothermally stratrified atmosphere. For slightly more realistic scenarios, where both the atmospheric parameters and the magnetic field vary spatially, the linear MHD equations typically cannot be solved analytically. We use the Lagrangian Remap code--a nonlinear, shock-capturing MHD code--to study the propagation of initially acoustic wavepackets through a model 2D atmosphere that includes a gravitationally stratified chromosphere, transition region, and low corona. The magnetic field is formed by three photospheric concentrations and includes a single magnetic null point, resulting in an inhomogeneous system with a magnetic dome topology. A portion of an introduced wavepacket will refract toward the null due to the varying Alfven speed. Waves incident on the equipartition contour surrounding the null, where the sound and Alfven speeds coincide, partially transmit, reflect, and mode convert between branches of the local dispersion relation. Outward propagating slow modes generated during conversion become strongly concentrated along the set of field lines passing near the null. Acoustic energy is beamed back downwards towards each photospheric foot point, and upwards along one separatrix that exits the top of the numerical domain. Changes in the dominant restoring force for the wavepacket, between the Lorentz and pressure gradient forces, lead to a buildup of current density along topologically important features of the system (the null point and its four separatrices) and can drive reconnection at the null point itself. Ohmic dissipation of the currents locally heats the plasma. We find that the amount of current accumulation depends on where the centroid of a wavepacket initial crosses the photosphere, but does not simply coincide with regions of open versus closed magnetic field or
Stability characteristics of jets in linearly-stratified, rotating fluids
Chen, Rui-Rong; Boyer, Don L.; Tao, Lijun
A series of laboratory experiments are conducted concerning an azimuthal jet of a linearly stratified rotating fluid in a cylindrical geometry. The jet is characterized by vertical and horizontal shear and the question of the stability of the flow is considered experimentally. The jet is driven by a source-sink method characterized by a volume flow rate of strength Q. BecauseQ has no direct geophysical significance a combined external set of dimensionless parameters is introduced. These include the Rossby, Richardson and Ekman numbers, the jet aspect ratio and two geometrical parameters. A RossbyRo against RichardsonRi number flow regime diagram is presented which shows that the wave mode of the instability generally decreases with increasingRo andRi, for fixedRi andRo, respectively. In accordance with Killworth's (1980) linear stability analysis, the wave mode for smallRi (Ri ⪉ 15) depends principally onRi with the instability being largely a baroclinic one. For largerRi(Ri ⪉ 100), again as predicted by Killworth's theory, the wave mode depends primarily onRo, the instability being a barotropic one. The regime diagram can be used to estimate the wave-length of jet instabilities in the atmosphere and oceans. These estimates suggest that the wave-lengths decrease with increasing jet velocity, decreasing jet width (equivalent to increasing horizontal shear) and increasing vertical shear, other parameters being fixed. An azimuthal topography aligned along the jet has the tendency to stabilize the jet in the sense that the amplitude of the instability is shown to be dramatically smaller in the presence of the topography, other parameters being fixed. The topography also tends to increase the wave-length of the instability. A scaling analysis is advanced, and supporting experimental data presented, relating the external and internal parameters utilized.
The Occupational Pension Schemes Survey 2006
Sarah Levy; David Miller
2008-01-01
Presents findings on the number of schemes, their membership and contributions to schemes by employers and employeesThis article presents findings on the number of occupational pension schemes in 2006, their membership and contributions to schemes by employers and employees. It is based on the Occupational Pension Schemes Annual Report (2006 edition). The findings distinguish between public and private sector schemes and include breakdowns by scheme status (open, closed, frozen or winding up)...
Implementing content constraints in alpha-stratified adaptive using a shadow test approach
Linden, van der Wim J.; Chang, Hua-Hua
2003-01-01
The methods of alpha-stratified adaptive testing and constrained adaptive testing with shadow tests are combined. The advantages are twofold: First, application of the shadow test approach allows the implementation of any type of constraint on item selection in alpha-stratified adaptive testing. Sec
van der Linden, Wim J.; Chang, Hua-Hua
The methods of alpha-stratified adaptive testing and constrained adaptive testing with shadow tests are combined in this study. The advantages are twofold. First, application of the shadow test allows the researcher to implement any type of constraint on item selection in alpha-stratified adaptive testing. Second, the result yields a simple set of…
Carmo, Carolina; Dumont, Olivier; Nielsen, Mads Pagh
2015-01-01
The use of stratified hot water tanks in solar energy systems - including ORC systems - as well as heat pump systems is paramount for a better performance of these systems. However, the availability of effective and reliable models to predict the annual performance of stratified hot water tanks c...
Lindsay, Colin R; Shaw, Emily; Walker, Ian; Johnson, Peter W M
2015-03-01
The implementation of stratified medicine in modern cancer care presents substantial opportunity to refine diagnosis and treatment but also numerous challenges. Through experience in a UK tumor profiling initiative, we have gained valuable insights into the complexities and possible solutions for routine delivery of stratified cancer medicine.
Optimal stratification of item pools in α-stratified computerized adaptive testing
Chang, Hua-Hua; Linden, van der Wim J.
2003-01-01
A method based on 0-1 linear programming (LP) is presented to stratify an item pool optimally for use in α-stratified adaptive testing. Because the 0-1 LP model belongs to the subclass of models with a network flow structure, efficient solutions are possible. The method is applied to a previous item
Properties of realized variance under alternative sampling schemes
Oomen, R.C.A.
2006-01-01
This paper investigates the statistical properties of the realized variance estimator in the presence of market microstructure noise. Different from the existing literature, the analysis relies on a pure jump process for high frequency security prices and explicitly distinguishes among alternative
Optimal spatial sampling scheme to characterize mine tailings
Debba, Pravesh
2009-08-01
Full Text Available to Characterize Mine Tailings Pravesh Debba1; Emmanuel John M. Carranza2; Alfred Stein2; Freek D. van der Meer2 1CSIR, Built Environment, Logisitics and Quantitative Methods, PO Box 395, Pretoria, 0001, South Africa. 2International Institute for Geo...-Information Science and Earth Observation (ITC), Hengelosestraat 99, PO Box 6, 7500 AA, Enschede, The Netherlands. E-mail: pdebba@csir.co.za; carranza@itc.nl; stein@itc.nl; vdmeer@itc.nl INTRODUCTION Geochemical characterization of mine waste impoundments...
Optimum sampling scheme for characterization of mine tailings
Debba, Pravesh
2009-07-01
Full Text Available FOR CHARACTERIZATION OF MINE TAILINGS P. Debba The Council for Scientific and Industrial Research (CSIR) CSIR Built Environment P. O. Box 395, 0001, South Africa email: pdebba@csir.co.za E.J.M. Carranza, A. Stein, F.D. van der Meer International Institute...: Exploration, Environment, Anal- ysis, vol. 3, no. 2, pp. 219–228, 2003. [3] P. Debba, E. J. M. Carranza, F. D. van der Meer, and A. Stein, “Abundance estimation of spectrally similar materials by using derivatives in simulated annealing,” IEEE Geoscience...
Properties of realized variance under alternative sampling schemes
Oomen, R.C.A.
2006-01-01
This paper investigates the statistical properties of the realized variance estimator in the presence of market microstructure noise. Different from the existing literature, the analysis relies on a pure jump process for high frequency security prices and explicitly distinguishes among alternative s
Schemes for Deterministic Polynomial Factoring
Ivanyos, Gábor; Saxena, Nitin
2008-01-01
In this work we relate the deterministic complexity of factoring polynomials (over finite fields) to certain combinatorial objects we call m-schemes. We extend the known conditional deterministic subexponential time polynomial factoring algorithm for finite fields to get an underlying m-scheme. We demonstrate how the properties of m-schemes relate to improvements in the deterministic complexity of factoring polynomials over finite fields assuming the generalized Riemann Hypothesis (GRH). In particular, we give the first deterministic polynomial time algorithm (assuming GRH) to find a nontrivial factor of a polynomial of prime degree n where (n-1) is a smooth number.
Coordinated renewable energy support schemes
Morthorst, P.E.; Jensen, S.G.
2006-01-01
This paper illustrates the effect that can be observed when support schemes for renewable energy are regionalised. Two theoretical examples are used to explain interactive effects on, e.g., the price of power, conditions for conventional power producers, and changes in import and export of power...... RES-E support schemes already has a common liberalised power market. In this case the introduction of a common support scheme for renewable technologies will lead to more efficient sitings of renewable plants, improving economic and environmental performance of the total power system...
Ríos, Antonio; López-Navas, Ana Isabel; López-López, Ana Isabel; Gómez, Francisco Javier; Iriarte, Jorge; Herruzo, Rafael; Blanco, Gerardo; Llorca, Francisco Javier; Asunsolo, Angel; Sánchez-Gallegos, Pilar; Gutiérrez, Pedro Ramón; Fernández, Ana; de Jesús, María Teresa; Martínez-Alarcón, Laura; Lana, Alberto; Fuentes, Lorena; Hernández, Juan Ramón; Virseda, Julio; Yelamos, José; Bondía, José Antonio; Hernández, Antonio Miguel; Ayala, Marco Antonio; Ramírez, Pablo; Parrilla, Pascual
2016-01-01
AIM: To analyze the attitude of Spanish medical students toward living liver donation (LLD) and to establish which factors have an influence on this attitude. METHODS: Study type: A sociological, interdisciplinary, multicenter and observational study. Study population: Medical students enrolled in Spain (n = 34000) in the university academic year 2010-2011. Sample size: A sample of 9598 students stratified by geographical area and academic year. Instrument used to measure attitude: A validated questionnaire (PCID-DVH RIOS) was self-administered and completed anonymously. Data collection procedure: Randomly selected medical schools. The questionnaire was applied to each academic year at compulsory sessions. Statistical analysis: Student´s t test, χ2 test and logistic regression analysis. RESULTS: The completion rate was 95.7% (n = 9275). 89% (n = 8258) were in favor of related LLD, and 32% (n = 2937) supported unrelated LLD. The following variables were associated with having a more favorable attitude: (1) age (P = 0.008); (2) sex (P mutilation of the body after donation (P < 0.001). CONCLUSION: Spanish medical students have a favorable attitude toward LLD. PMID:27433093
Provable Secure Identity Based Generalized Signcryption Scheme
Yu, Gang; Shen, Yong; Han, Wenbao
2010-01-01
According to actual needs, generalized signcryption scheme can flexibly work as an encryption scheme, a signature scheme or a signcryption scheme. In this paper, firstly, we give a security model for identity based generalized signcryption which is more complete than existing model. Secondly, we propose an identity based generalized signcryption scheme. Thirdly, we give the security proof of the new scheme in this complete model. Comparing with existing identity based generalized signcryption, the new scheme has less implementation complexity. Moreover, the new scheme has comparable computation complexity with the existing normal signcryption schemes.
Underground hydro scheme for Ullapool
无
2002-01-01
Scoltish and Southern Energy has awarded a contract for a new hydropower plant Scotland, the company's first hydro project since the 1960s. The S6 million scheme will be built by Miller Civil Engineering Services Ltd.
Rotbart, Noy Galil
evaluation of fully dynamic labeling schemes. Due to a connection between adjacency labeling schemes and the graph theoretical study of induced universal graphs, we study these in depth and show novel results for bounded degree graphs and power-law graphs. We also survey and make progress on the related......With ever increasing size of graphs, many distributed graph systems emerged to store, preprocess and analyze them. While such systems ease up congestion on servers, they incur certain penalties compared to centralized data structure. First, the total storage required to store a graph...... in a distributed fashion increases. Second, attempting to answer queries on vertices of a graph stored in a distributed fashion can be significantly more complicated. In order to lay theoretical foundations to the first penalty mentioned a large body of work concentrated on labeling schemes. A labeling scheme...
Capacity-achieving CPM schemes
Perotti, Alberto; Benedetto, Sergio; Montorsi, Guido
2008-01-01
The pragmatic approach to coded continuous-phase modulation (CPM) is proposed as a capacity-achieving low-complexity alternative to the serially-concatenated CPM (SC-CPM) coding scheme. In this paper, we first perform a selection of the best spectrally-efficient CPM modulations to be embedded into SC-CPM schemes. Then, we consider the pragmatic capacity (a.k.a. BICM capacity) of CPM modulations and optimize it through a careful design of the mapping between input bits and CPM waveforms. The so obtained schemes are cascaded with an outer serially-concatenated convolutional code to form a pragmatic coded-modulation system. The resulting schemes exhibit performance very close to the CPM capacity without requiring iterations between the outer decoder and the CPM demodulator. As a result, the receiver exhibits reduced complexity and increased flexibility due to the separation of the demodulation and decoding functions.
Good governance for pension schemes
Thornton, Paul
2011-01-01
Regulatory and market developments have transformed the way in which UK private sector pension schemes operate. This has increased demands on trustees and advisors and the trusteeship governance model must evolve in order to remain fit for purpose. This volume brings together leading practitioners to provide an overview of what today constitutes good governance for pension schemes, from both a legal and a practical perspective. It provides the reader with an appreciation of the distinctive characteristics of UK occupational pension schemes, how they sit within the capital markets and their social and fiduciary responsibilities. Providing a holistic analysis of pension risk, both from the trustee and the corporate perspective, the essays cover the crucial role of the employer covenant, financing and investment risk, developments in longevity risk hedging and insurance de-risking, and best practice scheme administration.
A Novel Iris Segmentation Scheme
Chen-Chung Liu
2014-01-01
Full Text Available One of the key steps in the iris recognition system is the accurate iris segmentation from its surrounding noises including pupil, sclera, eyelashes, and eyebrows of a captured eye-image. This paper presents a novel iris segmentation scheme which utilizes the orientation matching transform to outline the outer and inner iris boundaries initially. It then employs Delogne-Kåsa circle fitting (instead of the traditional Hough transform to further eliminate the outlier points to extract a more precise iris area from an eye-image. In the extracted iris region, the proposed scheme further utilizes the differences in the intensity and positional characteristics of the iris, eyelid, and eyelashes to detect and delete these noises. The scheme is then applied on iris image database, UBIRIS.v1. The experimental results show that the presented scheme provides a more effective and efficient iris segmentation than other conventional methods.
A Novel Digital Audio Watermarking Scheme in the Wavelet Domain
WANG Xiang-yang; YANG Hong-ying; ZHAO Hong
2005-01-01
We present a novel quantization-based digital audio watermarking scheme in wavelet domain. By quantizing a host audio's wavelet coefficients (Integer Lifting Wavelet Transform ) and utilizing the characteristics of human auditory system ( HAS), the gray image is embedded using our watermarking method. Experimental results show that the proposed watermarking scheme is inaudible and robust against various signal processing such as noising adding, lossy compression, low pass filtering, re-sampling, and re-quantifying.
An arbitrated quantum signature scheme
Zeng, G; Zeng, Guihua; Keitel, Christoph H.
2002-01-01
The general principle for a quantum signature scheme is proposed and investigated based on ideas from classical signature schemes and quantum cryptography. The suggested algorithm is implemented by a symmetrical quantum key cryptosystem and Greenberger-Horne-Zeilinger (GHZ) triplet states and relies on the availability of an arbitrator. We can guarantee the unconditional security of the algorithm, mostly due to the correlation of the GHZ triplet states and the use of quantum one-time pads.
Breeding schemes in reindeer husbandry
Lars Rönnegård
2003-04-01
Full Text Available The objective of the paper was to investigate annual genetic gain from selection (G, and the influence of selection on the inbreeding effective population size (Ne, for different possible breeding schemes within a reindeer herding district. The breeding schemes were analysed for different proportions of the population within a herding district included in the selection programme. Two different breeding schemes were analysed: an open nucleus scheme where males mix and mate between owner flocks, and a closed nucleus scheme where the males in non-selected owner flocks are culled to maximise G in the whole population. The theory of expected long-term genetic contributions was used and maternal effects were included in the analyses. Realistic parameter values were used for the population, modelled with 5000 reindeer in the population and a sex ratio of 14 adult females per male. The standard deviation of calf weights was 4.1 kg. Four different situations were explored and the results showed: 1. When the population was randomly culled, Ne equalled 2400. 2. When the whole population was selected on calf weights, Ne equalled 1700 and the total annual genetic gain (direct + maternal in calf weight was 0.42 kg. 3. For the open nucleus scheme, G increased monotonically from 0 to 0.42 kg as the proportion of the population included in the selection programme increased from 0 to 1.0, and Ne decreased correspondingly from 2400 to 1700. 4. In the closed nucleus scheme the lowest value of Ne was 1300. For a given proportion of the population included in the selection programme, the difference in G between a closed nucleus scheme and an open one was up to 0.13 kg. We conclude that for mass selection based on calf weights in herding districts with 2000 animals or more, there are no risks of inbreeding effects caused by selection.
Primary factors governing hydraulic fractures in heterogeneous stratified porous formations
Cleary, M.P.
1978-08-24
Some primary material, macrostructural and tectonic features of typical geological formations are identified, insofar as they affect the hydraulic fracturing operation whereby suitably treated fluid is pumped into massive crack(s) underground: the retardation or channeling due to strata interfaces, discontinuities and other heterogeneities is roughly characterized, in the context of fully three-dimensional crack shape evolution, and the initiation from oriented boreholes is discussed in detail. A general-purpose numerical scheme is described, efficiently based on a physically transparent distribution of discontinuity multipoles (or dislocations) and the solution of resulting singular integral equations, which permits precise quantification of these effects: in particular, the barriers provided by adjacent stiffer and tougher strata are properly rationalized and the roles of inelastic slippage, blunting, branching, arrest, and re-initiation are placed in more transparent perspective. Stabilization effects due to alterations of pore-fluid pressure (and hence effective decohering stress), or the flux of formation fluid into the open region near to the crack tip, are described as potentially unfavorable for hydrofrac containment. However, the dominant time-dependent mechanism of frac fluid penetration into the narrow crack aperture attracts most attention: this process is very naturally and tractably incorporated in our comprehensive numerical formulation so that realistic simulation of actual field operations should be feasible in the near future.
Indications for tonsillectomy stratified by the level of evidence
Windfuhr, Jochen P.
2016-01-01
Background: One of the most significant clinical trials, demonstrating the efficacy of tonsillectomy (TE) for recurrent throat infection in severely affected children, was published in 1984. This systematic review was undertaken to compile various indications for TE as suggested in the literature after 1984 and to stratify the papers according to the current concept of evidence-based medicine. Material and methods: A systematic Medline research was performed using the key word of “tonsillectomy“ in combination with different filters such as “systematic reviews“, “meta-analysis“, “English“, “German“, and “from 1984/01/01 to 2015/05/31“. Further research was performed in the Cochrane Database of Systematic Reviews, National Guideline Clearinghouse, Guidelines International Network and BMJ Clinical Evidence using the same key word. Finally, data from the “Trip Database” were researched for “tonsillectomy” and “indication“ and “from: 1984 to: 2015“ in combination with either “systematic review“ or “meta-analysis“ or “metaanalysis”. Results: A total of 237 papers were retrieved but only 57 matched our inclusion criteria covering the following topics: peritonsillar abscess (3), guidelines (5), otitis media with effusion (5), psoriasis (3), PFAPA syndrome (6), evidence-based indications (5), renal diseases (7), sleep-related breathing disorders (11), and tonsillitis/pharyngitis (12), respectively. Conclusions: 1) The literature suggests, that TE is not indicated to treat otitis media with effusion. 2) It has been shown, that the PFAPA syndrome is self-limiting and responds well to steroid administration, at least in a considerable amount of children. The indication for TE therefore appears to be imbalanced but further research is required to clarify the value of surgery. 3) Abscesstonsillectomy as a routine is not justified and indicated only for cases not responding to other measures of treatment, evident complications
Provable Secure Identity Based Generalized Signcryption Scheme
Yu, Gang; Ma, Xiaoxiao; Shen, Yong; Han, Wenbao
2010-01-01
According to actual needs, generalized signcryption scheme can flexibly work as an encryption scheme, a signature scheme or a signcryption scheme. In this paper, firstly, we give a security model for identity based generalized signcryption which is more complete than existing model. Secondly, we propose an identity based generalized signcryption scheme. Thirdly, we give the security proof of the new scheme in this complete model. Comparing with existing identity based generalized signcryption...
Transport Phenomena in Stratified Multi-Fluid Flow in the Presence and Absence of Gravity
Chigier, Norman; Humphrey, William
1996-01-01
Experiments are being conducted to study the effects of buoyancy on planar density-stratified shear flows. A wind tunnel generates planar flows separated by an insulating splitter plate, with either flow heated, which emerge from a two-dimensional nozzle. The objective is to isolate and define the effect of gravity and buoyancy on a stratified shear layer. To this end, both stably and unstably stratified layers will be investigated. This paper reports on the results of temperature and velocity measurements across the nozzle exit plane and downstream along the nozzle center plane.
Ahmad, Zahoor; Hanif, Muhammad
2013-01-01
The development of estimators of population parameters based on two-phase sampling schemes has seen a dramatic increase in the past decade. Various authors have developed estimators of population using either one or two auxiliary variables. The present volume is a comprehensive collection of estimators available in single and two phase sampling. The book covers estimators which utilize information on single, two and multiple auxiliary variables of both quantitative and qualitative nature. Th...
Multiuser switched diversity scheduling schemes
Shaqfeh, Mohammad
2012-09-01
Multiuser switched-diversity scheduling schemes were recently proposed in order to overcome the heavy feedback requirements of conventional opportunistic scheduling schemes by applying a threshold-based, distributed, and ordered scheduling mechanism. The main idea behind these schemes is that slight reduction in the prospected multiuser diversity gains is an acceptable trade-off for great savings in terms of required channel-state-information feedback messages. In this work, we characterize the achievable rate region of multiuser switched diversity systems and compare it with the rate region of full feedback multiuser diversity systems. We propose also a novel proportional fair multiuser switched-based scheduling scheme and we demonstrate that it can be optimized using a practical and distributed method to obtain the feedback thresholds. We finally demonstrate by numerical examples that switched-diversity scheduling schemes operate within 0.3 bits/sec/Hz from the ultimate network capacity of full feedback systems in Rayleigh fading conditions. © 2012 IEEE.
Optimal probabilistic dense coding schemes
Kögler, Roger A.; Neves, Leonardo
2017-04-01
Dense coding with non-maximally entangled states has been investigated in many different scenarios. We revisit this problem for protocols adopting the standard encoding scheme. In this case, the set of possible classical messages cannot be perfectly distinguished due to the non-orthogonality of the quantum states carrying them. So far, the decoding process has been approached in two ways: (i) The message is always inferred, but with an associated (minimum) error; (ii) the message is inferred without error, but only sometimes; in case of failure, nothing else is done. Here, we generalize on these approaches and propose novel optimal probabilistic decoding schemes. The first uses quantum-state separation to increase the distinguishability of the messages with an optimal success probability. This scheme is shown to include (i) and (ii) as special cases and continuously interpolate between them, which enables the decoder to trade-off between the level of confidence desired to identify the received messages and the success probability for doing so. The second scheme, called multistage decoding, applies only for qudits ( d-level quantum systems with d>2) and consists of further attempts in the state identification process in case of failure in the first one. We show that this scheme is advantageous over (ii) as it increases the mutual information between the sender and receiver.
Energy partitioning schemes: a dilemma.
Mayer, I
2007-01-01
Two closely related energy partitioning schemes, in which the total energy is presented as a sum of atomic and diatomic contributions by using the "atomic decomposition of identity", are compared on the example of N,N-dimethylformamide, a simple but chemically rich molecule. Both schemes account for different intramolecular interactions, for instance they identify the weak C-H...O intramolecular interactions, but give completely different numbers. (The energy decomposition scheme based on the virial theorem is also considered.) The comparison of the two schemes resulted in a dilemma which is especially striking when these schemes are applied for molecules distorted from their equilibrium structures: one either gets numbers which are "on the chemical scale" and have quite appealing values at the equilibrium molecular geometries, but exhibiting a counter-intuitive distance dependence (the two-center energy components increase in absolute value with the increase of the interatomic distances)--or numbers with too large absolute values but "correct" distance behaviour. The problem is connected with the quick decay of the diatomic kinetic energy components.
Royle, J. Andrew; Sutherland, Christopher S.; Fuller, Angela K.; Sun, Catherine C.
2015-01-01
We develop a likelihood analysis framework for fitting spatial capture-recapture (SCR) models to data collected on class structured or stratified populations. Our interest is motivated by the necessity of accommodating the problem of missing observations of individual class membership. This is particularly problematic in SCR data arising from DNA analysis of scat, hair or other material, which frequently yields individual identity but fails to identify the sex. Moreover, this can represent a large fraction of the data and, given the typically small sample sizes of many capture-recapture studies based on DNA information, utilization of the data with missing sex information is necessary. We develop the class structured likelihood for the case of missing covariate values, and then we address the scaling of the likelihood so that models with and without class structured parameters can be formally compared regardless of missing values. We apply our class structured model to black bear data collected in New York in which sex could be determined for only 62 of 169 uniquely identified individuals. The models containing sex-specificity of both the intercept of the SCR encounter probability model and the distance coefficient, and including a behavioral response are strongly favored by log-likelihood. Estimated population sex ratio is strongly influenced by sex structure in model parameters illustrating the importance of rigorous modeling of sex differences in capture-recapture models.
Eckmann, Madeleine; Dunham, Jason; Connor, Edward J.; Welch, Carmen A.
2016-01-01
Many species living in deeper lentic ecosystems exhibit daily movements that cycle through the water column, generally referred to as diel vertical migration (DVM). In this study, we applied bioenergetics modelling to evaluate growth as a hypothesis to explain DVM by bull trout (Salvelinus confluentus) in a thermally stratified reservoir (Ross Lake, WA, USA) during the peak of thermal stratification in July and August. Bioenergetics model parameters were derived from observed vertical distributions of temperature, prey and bull trout. Field sampling confirmed that bull trout prey almost exclusively on recently introduced redside shiner (Richardsonius balteatus). Model predictions revealed that deeper (>25 m) DVMs commonly exhibited by bull trout during peak thermal stratification cannot be explained by maximising growth. Survival, another common explanation for DVM, may have influenced bull trout depth use, but observations suggest there may be additional drivers of DVM. We propose these deeper summertime excursions may be partly explained by an alternative hypothesis: the importance of colder water for gametogenesis. In Ross Lake, reliance of bull trout on warm water prey (redside shiner) for consumption and growth poses a potential trade-off with the need for colder water for gametogenesis.
Airway microbiota and pathogen abundance in age-stratified cystic fibrosis patients.
Cox, Michael J; Allgaier, Martin; Taylor, Byron; Baek, Marshall S; Huang, Yvonne J; Daly, Rebecca A; Karaoz, Ulas; Andersen, Gary L; Brown, Ronald; Fujimura, Kei E; Wu, Brian; Tran, Diem; Koff, Jonathan; Kleinhenz, Mary Ellen; Nielson, Dennis; Brodie, Eoin L; Lynch, Susan V
2010-06-23
Bacterial communities in the airways of cystic fibrosis (CF) patients are, as in other ecological niches, influenced by autogenic and allogenic factors. However, our understanding of microbial colonization in younger versus older CF airways and the association with pulmonary function is rudimentary at best. Using a phylogenetic microarray, we examine the airway microbiota in age stratified CF patients ranging from neonates (9 months) to adults (72 years). From a cohort of clinically stable patients, we demonstrate that older CF patients who exhibit poorer pulmonary function possess more uneven, phylogenetically-clustered airway communities, compared to younger patients. Using longitudinal samples collected form a subset of these patients a pattern of initial bacterial community diversification was observed in younger patients compared with a progressive loss of diversity over time in older patients. We describe in detail the distinct bacterial community profiles associated with young and old CF patients with a particular focus on the differences between respective "early" and "late" colonizing organisms. Finally we assess the influence of Cystic Fibrosis Transmembrane Regulator (CFTR) mutation on bacterial abundance and identify genotype-specific communities involving members of the Pseudomonadaceae, Xanthomonadaceae, Moraxellaceae and Enterobacteriaceae amongst others. Data presented here provides insights into the CF airway microbiota, including initial diversification events in younger patients and establishment of specialized communities of pathogens associated with poor pulmonary function in older patient populations.
Airway microbiota and pathogen abundance in age-stratified cystic fibrosis patients.
Michael J Cox
Full Text Available Bacterial communities in the airways of cystic fibrosis (CF patients are, as in other ecological niches, influenced by autogenic and allogenic factors. However, our understanding of microbial colonization in younger versus older CF airways and the association with pulmonary function is rudimentary at best. Using a phylogenetic microarray, we examine the airway microbiota in age stratified CF patients ranging from neonates (9 months to adults (72 years. From a cohort of clinically stable patients, we demonstrate that older CF patients who exhibit poorer pulmonary function possess more uneven, phylogenetically-clustered airway communities, compared to younger patients. Using longitudinal samples collected form a subset of these patients a pattern of initial bacterial community diversification was observed in younger patients compared with a progressive loss of diversity over time in older patients. We describe in detail the distinct bacterial community profiles associated with young and old CF patients with a particular focus on the differences between respective "early" and "late" colonizing organisms. Finally we assess the influence of Cystic Fibrosis Transmembrane Regulator (CFTR mutation on bacterial abundance and identify genotype-specific communities involving members of the Pseudomonadaceae, Xanthomonadaceae, Moraxellaceae and Enterobacteriaceae amongst others. Data presented here provides insights into the CF airway microbiota, including initial diversification events in younger patients and establishment of specialized communities of pathogens associated with poor pulmonary function in older patient populations.
Kreitinger, Elizabeth A.; Kappel, William M.
2014-01-01
The Village of Endicott, New York, is seeking an alternate source of public drinking water with the potential to supplement their current supply, which requires treatment due to legacy contamination. The southerly-draining Nanticoke Creek valley, located north of the village, was identified as a potential water source and the local stratified-drift (valley fill) aquifer was investigated to determine its hydrogeologic and water-quality characteristics. Nanticoke Creek and its aquifer extend from the hamlet of Glen Aubrey, N.Y., to the village of Endicott, a distance of about 15 miles, where it joins the Susquehanna River and its aquifer. The glacial sediments that comprise the stratified-drift aquifer vary in thickness and are generally underlain by glacial till over Devonian-aged shale and siltstone. Groundwater is more plentiful in the northern part of the aquifer where sand and gravel deposits are generally more permeable than in the southern part of the aquifer where less-permeable unconsolidated deposits are found. Generally there is enough groundwater to supply most homeowner wells and in some cases, supply small public-water systems such as schools, mobile-home parks, and small commercial/industrial facilities. The aquifer is recharged by precipitation, runoff, and tributary streams. Most tributary streams flowing across alluvial deposits lose water to the aquifer as they flow off of their bedrock-lined channels and into the more permeable alluvial deposits at the edges of the valley. The quality of both surface water and groundwater is generally good. Some water wells do have water-quality issues related to natural constituents (manganese and iron) and several homeowners noted either the smell and (or) taste of hydrogen sulfide in their drinking water. Dissolved methane concentrations from five drinking-water wells were well below the potentially explosive value of 28 milligrams per liter. Samples from surface and groundwater met nearly all State and Federal
Morphological sampling of closed sets:
Christian Ronse; Mohamed Tajine
2004-01-01
We briefiy survey the standard morphological approach (Heijmans, 1994) to the sampling (or discretization) of sets. Then we summarize the main results of our metric theory of sampling (Ronse and Tajine, 2000; 2001; 2002; Tajine and Ronse, 2002), which can be used to analyse several sampling schemes, in particular the morphological one. We extend it to the sampling of closed sets (instead of compact ones), and to the case where the sampling subspace is boundedly compact (instead of boundedly f...
Vertical stratification of bacteria and archaea in sediments of a boreal stratified humic lake
Rissanen, Antti J.; Mpamah, Promise; Peura, Sari; Taipale, Sami; Biasi, Christina; Nykänen, Hannu
2015-04-01
Boreal stratified humic lakes, with steep redox gradients in the water column and in the sediment, are important sources of methane (CH4) to the atmosphere. CH4 flux from these lakes is largely controlled by the balance between CH4-production (methanogenesis), which takes place in the organic rich sediment and in the deepest water layers, and CH4-consumption (methanotrophy), which takes place mainly in the water column. While there is already some published information on the activity, diversity and community structure of bacteria in the water columns of these lakes, such information on sediment microbial communities is very scarce. This study aims to characterize the vertical variation patterns in the diversity and the structure of microbial communities in sediment of a boreal stratified lake. Particular focus is on microbes with the potential to contribute to methanogenesis (fermentative bacteria and methanogenic archaea) and to methanotrophy (methanotrophic bacteria and archaea). Two sediment cores (26 cm deep), collected from the deepest point (~6 m) of a small boreal stratified lake during winter-stratification, were divided into depth sections of 1 to 2 cm for analyses. Communities were studied from DNA extracted from sediment samples by next-generation sequencing (Ion Torrent) of polymerase chain reaction (PCR) - amplified bacterial and archaeal 16S rRNA gene amplicons. The abundance of methanogenic archaea was also specifically studied by quantitative-PCR of methyl coenzyme-M reductase gene (mcrA) amplicons. Furthermore, the community structure and the abundance of bacteria were studied by phospholipid fatty acid (PLFA) analysis. Dominant potential fermentative bacteria belonged to families Syntrophaceae, Clostridiaceae and Peptostreptococcaceae. There were considerable differences in the vertical distribution among these groups. The relative abundance of Syntrophaceae started to increase from the sediment surface, peaked at depth layer from 5 to 10 cm (up
Superposition Enhanced Nested Sampling
Stefano Martiniani
2014-08-01
Full Text Available The theoretical analysis of many problems in physics, astronomy, and applied mathematics requires an efficient numerical exploration of multimodal parameter spaces that exhibit broken ergodicity. Monte Carlo methods are widely used to deal with these classes of problems, but such simulations suffer from a ubiquitous sampling problem: The probability of sampling a particular state is proportional to its entropic weight. Devising an algorithm capable of sampling efficiently the full phase space is a long-standing problem. Here, we report a new hybrid method for the exploration of multimodal parameter spaces exhibiting broken ergodicity. Superposition enhanced nested sampling combines the strengths of global optimization with the unbiased or athermal sampling of nested sampling, greatly enhancing its efficiency with no additional parameters. We report extensive tests of this new approach for atomic clusters that are known to have energy landscapes for which conventional sampling schemes suffer from broken ergodicity. We also introduce a novel parallelization algorithm for nested sampling.
Murawski, Aline; Bürger, Gerd; Vorogushyn, Sergiy; Merz, Bruno
2016-04-01
The use of a weather pattern based approach for downscaling of coarse, gridded atmospheric data, as usually obtained from the output of general circulation models (GCM), allows for investigating the impact of anthropogenic greenhouse gas emissions on fluxes and state variables of the hydrological cycle such as e.g. on runoff in large river catchments. Here we aim at attributing changes in high flows in the Rhine catchment to anthropogenic climate change. Therefore we run an objective classification scheme (simulated annealing and diversified randomisation - SANDRA, available from the cost733 classification software) on ERA20C reanalyses data and apply the established classification to GCMs from the CMIP5 project. After deriving weather pattern time series from GCM runs using forcing from all greenhouse gases (All-Hist) and using natural greenhouse gas forcing only (Nat-Hist), a weather generator will be employed to obtain climate data time series for the hydrological model. The parameters of the weather pattern classification (i.e. spatial extent, number of patterns, classification variables) need to be selected in a way that allows for good stratification of the meteorological variables that are of interest for the hydrological modelling. We evaluate the skill of the classification in stratifying meteorological data using a multi-variable approach. This allows for estimating the stratification skill for all meteorological variables together, not separately as usually done in existing similar work. The advantage of the multi-variable approach is to properly account for situations where e.g. two patterns are associated with similar mean daily temperature, but one pattern is dry while the other one is related to considerable amounts of precipitation. Thus, the separation of these two patterns would not be justified when considering temperature only, but is perfectly reasonable when accounting for precipitation as well. Besides that, the weather patterns derived from
Distance labeling schemes for trees
Alstrup, Stephen; Gørtz, Inge Li; Bistrup Halvorsen, Esben
2016-01-01
We consider distance labeling schemes for trees: given a tree with n nodes, label the nodes with binary strings such that, given the labels of any two nodes, one can determine, by looking only at the labels, the distance in the tree between the two nodes. A lower bound by Gavoille et al. [Gavoille...... variants such as, for example, small distances in trees [Alstrup et al., SODA, 2003]. We improve the known upper and lower bounds of exact distance labeling by showing that 1/4 log2(n) bits are needed and that 1/2 log2(n) bits are sufficient. We also give (1 + ε)-stretch labeling schemes using Theta......(log(n)) bits for constant ε> 0. (1 + ε)-stretch labeling schemes with polylogarithmic label size have previously been established for doubling dimension graphs by Talwar [Talwar, STOC, 2004]. In addition, we present matching upper and lower bounds for distance labeling for caterpillars, showing that labels...
QIU Xiang
2006-01-01
Turbulence structures and turbulent Counter-Gradient Transport(CGT) properties in the stratified flows with a sharp temperature interface are investigated by experimental measurements using LIF and PIV, by LES and by correlation analysis.
Development of a Curved, Stratified, In Vitro Model to Assess Ocular Biocompatibility: e96448
Cameron K Postnikoff; Robert Pintwala; Sara Williams; Ann M Wright; Denise Hileeto; Maud B Gorbet
2014-01-01
.... Methods Immortalized human corneal epithelial cells were grown to confluency on curved cellulose filters for seven days, and were then differentiated and stratified using an air-liquid interface...
Banakh, Taras
2008-01-01
We introduce and study (metrically) quarter-stratifiable spaces and then apply them to generalize Rudin and Kuratowski-Montgomery theorems about the Baire and Borel complexity of separately continuous functions.
Stratified shear flow in an inclined duct: coherent structures and mixing
Lefauve, Adrien; Partridge, Jamie; Dalziel, Stuart; Linden, Paul
2016-11-01
We present laboratory experiments on the exchange flow in an inclined square duct connecting two reservoirs at different densities. This system generates and maintains a stratified shear flow, which can be laminar, wavy or turbulent depending on the density difference and inclination angle. It is believed that the mean dissipation is set by the angle, and that high buoyancy Reynolds numbers (i.e. turbulent intensity) can be maintained, making this system suited for the study of continuously forced stratified turbulence. The talk will focus on the analysis of time-resolved, near-instantaneous 3D velocity and density data obtained by stereo particle image velocimetry (PIV) and laser induced fluorescence (LIF). This data allow for the visualisation of 3D coherent structures as well as turbulent mixing properties, which are key in understanding the dynamics of stratified turbulence. Supported by EPSRC Programme Grant EP/K034529/1 entitled "Mathematical Underpinnings of Stratified Turbulence".
Shudo, Toshio [Applied Energy System Group, Division of Energy and Environmental Systems, Hokkaido University, N13 W8 Kita-Ward, Sapporo, Hokkaido 060-8628 (Japan); Oba, Shuji [Mazda Motor Corporation, Hiroshima 730-8670 (Japan)
2009-03-15
Reduction in cooling loss due to the heat transfer from burning gas to the combustion chamber wall is very important for improving the thermal efficiency in hydrogen engines. The previous research has shown that the direct injection stratified charge can be a technique to reduce the cooling loss and improve thermal efficiency in hydrogen combustion. For effective reductions in cooling loss by the stratified charge, it is very important to know the relation between the fuel injection conditions and mixture distribution. The current research employs the laser induced breakdown spectroscopy as a method to measure the hydrogen concentration distribution in the direct injection stratified charge. Measurement of instantaneous local equivalence ratio by the method clears the characteristics of mixture formation in hydrogen direct injection stratified charge. This research also tries to actively control the mixture distribution using a split fuel injection. (author)
Fugel, Hans-Joerg; Nuijten, Mark; Postma, Maarten
2016-01-01
RATIONALE: Stratified Medicine (SM) is becoming a natural result of advances in biomedical science and a promising path for the innovation-based biopharmaceutical industry to create new investment opportunities. While the use of biomarkers to improve R&D efficiency and productivity is very much
Electrical Injection Schemes for Nanolasers
Lupi, Alexandra; Chung, Il-Sug; Yvind, Kresten
2014-01-01
Three electrical injection schemes based on recently demonstrated electrically pumped photonic crystal nanolasers have been numerically investigated: 1) a vertical p-i-n junction through a post structure; 2) a lateral p-i-n junction with a homostructure; and 3) a lateral p-i-n junction....... For this analysis, the properties of different schemes, i.e., electrical resistance, threshold voltage, threshold current, and internal efficiency as energy requirements for optical interconnects are compared and the physics behind the differences is discussed....
Small-scale classification schemes
Hertzum, Morten
2004-01-01
. While coordination mechanisms focus on how classification schemes enable cooperation among people pursuing a common goal, boundary objects embrace the implicit consequences of classification schemes in situations involving conflicting goals. Moreover, the requirements specification focused on functional...... requirements and provided little information about why these requirements were considered relevant. This stands in contrast to the discussions at the project meetings where the software engineers made frequent use of both abstract goal descriptions and concrete examples to make sense of the requirements....... This difference between the written requirements specification and the oral discussions at the meetings may help explain software engineers general preference for people, rather than documents, as their information sources....
Stekl, Peter J.; Flanagan, Sarah M.
1992-01-01
-water-level measurements and collect ground-water-quality samples. Surface-water-discharge measurements were made at 16 sites during low flow when the surface water is primarily ground-water discharge . These low-flow measurements indicate quantities of ground water potentially available from aquifers. Hydraulic conductivities of aquifer materials were estimated from grain-size-distribution data from 61 samples of stratified drift . Transmissivity was estimated from well logs by assigning hydraulic conductivity to specific well-log intervals, multiplying by the saturated thickness of the interval, and summing the results . Additional transmissivity values were obtained from an analysis of specific capacity and aquifer-test data. Long-term aquifer yields and contributing areas to hypothetical supply wells were estimated by application of a method that is analogous to super position and incorporates a ground-water-flow model developed by McDonald and Harbaugh (1988) . This method was applied to two aquifers judged to have the best potential for providing additional ground-water supplies. Samples of ground water from 26 test wells and 4 municipal wells were collected in March and August 1987 for analysis of common inorganic, organic, and volatile organic constituents. Methods for collecting and analyzing the samples are described by Fishman and Freidman (1989) . The water-quality results from the well samples were used to characterize background water quality in the stratified-drift aquifers.
A Fast Implicit Integration Scheme to Solve Highly Nonlinear System
Siddiquee, Saiful
Now-a-days researchers are formulating new generation of soil-models based on combined theory. That means researchers are trying to put forward a unified material model, which would predict at least the behaviour of all types of soils under all types of stress and time paths. So the solution techniques so far being used by the nonlinear Finite Element packages no longer can meet the huge demand of computational speed created by those models. It was necessary to develop a new type of solution scheme for the sophisticated models. Usually material nonlinearity makes it difficult to create a robust solution technique. So it is important to develop a solution scheme which will be very robust at the same time. That means the solution scheme should not break-down even for a notoriously complicated unified model. In this paper, we have developed an implicit solution scheme, which solves the resulting nonlinear equations of motion by implicit dynamic relaxation. There are a myriad number of implicit schemes for the use. Here a relatively less used method—called "Houbolt's integration scheme" has been used. It is very similar to the central difference scheme only difference is the use of the higher-order terms in the definition of velocity and acceleration. In order to make it faster, sparse-matrix solution scheme is used with partial pivoting and reordering of matrix elements to minimize the fill-ins. The combined effect is quite dramatic. It provides the main two traits of a good nonlinear solution technique—i.e., speed and robustness of solution. The solution scheme is applied to trace the full loading path of an elasto-visco-plastically defined material behaviour of a Plane Strain Compression (PSC) test sample. There is a huge gain in speed and robustness compared to the other techniques of solution.
Sequential sampling: a novel method in farm animal welfare assessment.
Heath, C A E; Main, D C J; Mullan, S; Haskell, M J; Browne, W J
2016-02-01
Lameness in dairy cows is an important welfare issue. As part of a welfare assessment, herd level lameness prevalence can be estimated from scoring a sample of animals, where higher levels of accuracy are associated with larger sample sizes. As the financial cost is related to the number of cows sampled, smaller samples are preferred. Sequential sampling schemes have been used for informing decision making in clinical trials. Sequential sampling involves taking samples in stages, where sampling can stop early depending on the estimated lameness prevalence. When welfare assessment is used for a pass/fail decision, a similar approach could be applied to reduce the overall sample size. The sampling schemes proposed here apply the principles of sequential sampling within a diagnostic testing framework. This study develops three sequential sampling schemes of increasing complexity to classify 80 fully assessed UK dairy farms, each with known lameness prevalence. Using the Welfare Quality herd-size-based sampling scheme, the first 'basic' scheme involves two sampling events. At the first sampling event half the Welfare Quality sample size is drawn, and then depending on the outcome, sampling either stops or is continued and the same number of animals is sampled again. In the second 'cautious' scheme, an adaptation is made to ensure that correctly classifying a farm as 'bad' is done with greater certainty. The third scheme is the only scheme to go beyond lameness as a binary measure and investigates the potential for increasing accuracy by incorporating the number of severely lame cows into the decision. The three schemes are evaluated with respect to accuracy and average sample size by running 100 000 simulations for each scheme, and a comparison is made with the fixed size Welfare Quality herd-size-based sampling scheme. All three schemes performed almost as well as the fixed size scheme but with much smaller average sample sizes. For the third scheme, an overall
Efficient adaptive fuzzy control scheme
Papp, Z.; Driessen, B.J.F.
1995-01-01
The paper presents an adaptive nonlinear (state-) feedback control structure, where the nonlinearities are implemented as smooth fuzzy mappings defined as rule sets. The fine tuning and adaption of the controller is realized by an indirect adaptive scheme, which modifies the parameters of the fuzzy
Homogenization scheme for acoustic metamaterials
Yang, Min
2014-02-26
We present a homogenization scheme for acoustic metamaterials that is based on reproducing the lowest orders of scattering amplitudes from a finite volume of metamaterials. This approach is noted to differ significantly from that of coherent potential approximation, which is based on adjusting the effective-medium parameters to minimize scatterings in the long-wavelength limit. With the aid of metamaterials’ eigenstates, the effective parameters, such as mass density and elastic modulus can be obtained by matching the surface responses of a metamaterial\\'s structural unit cell with a piece of homogenized material. From the Green\\'s theorem applied to the exterior domain problem, matching the surface responses is noted to be the same as reproducing the scattering amplitudes. We verify our scheme by applying it to three different examples: a layered lattice, a two-dimensional hexagonal lattice, and a decorated-membrane system. It is shown that the predicted characteristics and wave fields agree almost exactly with numerical simulations and experiments and the scheme\\'s validity is constrained by the number of dominant surface multipoles instead of the usual long-wavelength assumption. In particular, the validity extends to the full band in one dimension and to regimes near the boundaries of the Brillouin zone in two dimensions.
Distance labeling schemes for trees
Alstrup, Stephen; Gørtz, Inge Li; Bistrup Halvorsen, Esben;
2016-01-01
We consider distance labeling schemes for trees: given a tree with n nodes, label the nodes with binary strings such that, given the labels of any two nodes, one can determine, by looking only at the labels, the distance in the tree between the two nodes. A lower bound by Gavoille et al. [Gavoill...
Distance labeling schemes for trees
Alstrup, Stephen; Gørtz, Inge Li; Bistrup Halvorsen, Esben
2016-01-01
variants such as, for example, small distances in trees [Alstrup et al., SODA, 2003]. We improve the known upper and lower bounds of exact distance labeling by showing that 1/4 log2(n) bits are needed and that 1/2 log2(n) bits are sufficient. We also give (1 + ε)-stretch labeling schemes using Theta...
Quantum group blind signature scheme without entanglement
Xu, Rui; Huang, Liusheng; Yang, Wei; He, Libao
2011-07-01
In this paper we propose a quantum group blind signature scheme designed for distributed e-voting system. Our scheme combines the properties of group signature and blind signature to provide anonymity of voters in an e-voting system. The unconditional security of our scheme is ensured by quantum mechanics. Without employing entanglement, the proposed scheme is easier to be realized comparing with other quantum signature schemes.
Fair Electronic Payment Scheme Based on DSA
WANG Shao-bin; HONG Fan; ZHU Xian
2005-01-01
We present a multi-signature scheme based on DSA and describes a fair electronic payment scheme based on improved DSA signatures. The scheme makes both sides in equal positions during the course of electronic transaction. A Trusted Third Party (TTP) is involved in the scheme to guarantee the fairness of the scheme for both sides. However, only during the course of registration and dispute resolution will TTP be needed. TTP is not needed during the normal payment stage.
Simulation model of stratified thermal energy storage tank using finite difference method
Waluyo, Joko
2016-06-01
Stratified TES tank is normally used in the cogeneration plant. The stratified TES tanks are simple, low cost, and equal or superior in thermal performance. The advantage of TES tank is that it enables shifting of energy usage from off-peak demand for on-peak demand requirement. To increase energy utilization in a stratified TES tank, it is required to build a simulation model which capable to simulate the charging phenomenon in the stratified TES tank precisely. This paper is aimed to develop a novel model in addressing the aforementioned problem. The model incorporated chiller into the charging of stratified TES tank system in a closed system. The model was developed in one-dimensional type involve with heat transfer aspect. The model covers the main factors affect to degradation of temperature distribution namely conduction through the tank wall, conduction between cool and warm water, mixing effect on the initial flow of the charging as well as heat loss to surrounding. The simulation model is developed based on finite difference method utilizing buffer concept theory and solved in explicit method. Validation of the simulation model is carried out using observed data obtained from operating stratified TES tank in cogeneration plant. The temperature distribution of the model capable of representing S-curve pattern as well as simulating decreased charging temperature after reaching full condition. The coefficient of determination values between the observed data and model obtained higher than 0.88. Meaning that the model has capability in simulating the charging phenomenon in the stratified TES tank. The model is not only capable of generating temperature distribution but also can be enhanced for representing transient condition during the charging of stratified TES tank. This successful model can be addressed for solving the limitation temperature occurs in charging of the stratified TES tank with the absorption chiller. Further, the stratified TES tank can be
Emad W. Al-Shalabi
2016-01-01
Full Text Available Oil recovery prediction and field pilot implements require basic understanding and estimation of displacement efficiency. Corefloods and glass micromodels are two of the commonly used experimental methods to achieve this. In this paper, waterflood recovery is investigated using layered etched glass micromodel and Berea sandstone core plugs with large permeability contrasts. This study focuses mainly on the effect of permeability (heterogeneity in stratified porous media with no cross-flow. Three experimental setups were designed to represent uniformly stratified oil reservoir with vertical discontinuity in permeability. Waterflood recovery to residual oil saturation (Sor is measured through glass micromodel (to aid visual observation, linear coreflood, and forced drainage-imbibition processes by ultracentrifuge. Six oil samples of low-to-medium viscosity and porous media of widely different permeability (darcy and millidarcy ranges were chosen for the study. The results showed that waterflood displacement efficiencies are consistent in both permeability ranges, namely, glass micromodel and Berea sandstone core plugs. Interestingly, the experimental results show that the low permeability zones resulted in higher ultimate oil recovery compared to high permeability zones. At Sor microheterogeneity and fingering are attributed for this phenomenon. In light of the findings, conformance control is discussed for better sweep efficiency. This paper may be of help to field operators to gain more insight into microheterogeneity and fingering phenomena and their impact on waterflood recovery estimation.
Bugliosi, Edward F.; Miller, Todd S.; Reynolds, Richard J.
2014-01-01
The lithology, areal extent, and the water-table configuration in stratified-drift aquifers in the northern part of the Pony Hollow Creek valley in the Town of Newfield, New York, were mapped as part of an ongoing aquifer mapping program in Tompkins County. Surficial geologic and soil maps, well and test-boring records, light detection and ranging (lidar) data, water-level measurements, and passive-seismic surveys were used to map the aquifer geometry, construct geologic sections, and determine the depth to bedrock at selected locations throughout the valley. Additionally, water-quality samples were collected from selected streams and wells to characterize the quality of surface and groundwater in the study area. Sedimentary bedrock underlies the study area and is overlain by unstratified drift (till), stratified drift (glaciolacustrine and glaciofluvial deposits), and recent post glacial alluvium. The major type of unconsolidated, water-yielding material in the study area is stratified drift, which consists of glaciofluvial sand and gravel, and is present in sufficient amounts in most places to form an extensive unconfined aquifer throughout the study area, which is the source of water for most residents, farms, and businesses in the valleys. A map of the water table in the unconfined aquifer was constructed by using (1) measurements made between the mid-1960s through 2010, (2) control on the altitudes of perennial streams at 10-foot contour intervals from lidar data collected by Tompkins County, and (3) water surfaces of ponds and wetlands that are hydraulically connected to the unconfined aquifer. Water-table contours indicate that the direction of groundwater flow within the stratified-drift aquifer is predominantly from the valley walls toward the streams and ponds in the central part of the valley where groundwater then flows southwestward (down valley) toward the confluence with the Cayuta Creek valley. Locally, the direction of groundwater flow is radially
Nonlinear multiresolution signal decomposition schemes--part I: morphological pyramids.
Goutsias, J; Heijmans, H M
2000-01-01
Interest in multiresolution techniques for signal processing and analysis is increasing steadily. An important instance of such a technique is the so-called pyramid decomposition scheme. This paper presents a general theory for constructing linear as well as nonlinear pyramid decomposition schemes for signal analysis and synthesis. The proposed theory is based on the following ingredients: 1) the pyramid consists of a (finite or infinite) number of levels such that the information content decreases toward higher levels and 2) each step toward a higher level is implemented by an (information-reducing) analysis operator, whereas each step toward a lower level is implemented by an (information-preserving) synthesis operator. One basic assumption is necessary: synthesis followed by analysis yields the identity operator, meaning that no information is lost by these two consecutive steps. Several examples of pyramid decomposition schemes are shown to be instances of the proposed theory: a particular class of linear pyramids, morphological skeleton decompositions, the morphological Haar pyramid, median pyramids, etc. Furthermore, the paper makes a distinction between single-scale and multiscale decomposition schemes, i.e., schemes without or with sample reduction. Finally, the proposed theory provides the foundation of a general approach to constructing nonlinear wavelet decomposition schemes and filter banks.
WEIGHTED COMPACT SCHEME FOR SHOCK CAPTURING
无
2001-01-01
A new class of finite difference schemes--the weighted compact schemes are proposed. According to the idea of the WENO schemes, the weighted compact scheme is constructed by a combination of the approximations of derivatives on candidate stencils with properly assigned weights so that the non-oscillatory property is achieved when discontinuities appear. The primitive function reconstruction method of ENO schemes is applied to obtain the conservative form of the weighted compact scheme. This new scheme not only preserves the characteristic of standard compact schemes and achieves high order accuracy and high resolution using a compact stencil,but also can accurately capture shock waves and discontinuities without oscillation, Numerical examples show that the new scheme is very promising and successful.``
Haralambous, Yannis
2012-01-01
We present an extension of the Explicit Semantic Analysis method by Gabrilovich and Markovitch. Using their semantic relatedness measure, we weight the Wikipedia categories graph. Then, we extract a minimal spanning tree, using Chu-Liu-Edmonds' algorithm. We define a notion of stratified tfidf where the stratas, for a given Wikipedia page and a given term, are the classical tfidf and categorical tfidfs of the term in the ancestor categories of the page (ancestors in the sense of the minimal spanning tree). Our method is based on this stratified tfidf, which adds extra weight to terms that "survive" when climbing up the category tree. We evaluate our method by a text classification on the WikiNews corpus: it increases precision by 18%. Finally, we provide hints for future research.
Dual Watermarking Scheme with Encryption
Dhanalakshmi, R
2010-01-01
Digital Watermarking is used for copyright protection and authentication. In the proposed system, a Dual Watermarking Scheme based on DWT SVD with chaos encryption algorithm, will be developed to improve the robustness and protection along with security. DWT and SVD have been used as a mathematical tool to embed watermark in the image. Two watermarks are embedded in the host image. The secondary is embedded into primary watermark and the resultant watermarked image is encrypted using chaos based logistic map. This provides an efficient and secure way for image encryption and transmission. The watermarked image is decrypted and a reliable watermark extraction scheme is developed for the extraction of the primary as well as secondary watermark from the distorted image.
Ion Polarization Scheme for MEIC
Kondratenko, A M; Filatov, Yu N; Derbenev, Ya S; Lin, F; Morozov, V S; Zhang, Y
2016-01-01
The choice of a figure 8 shape for the booster and collider rings of MEIC opens wide possibilities for preservation of the ion polarization during beam acceleration as well as for control of the polarization at the collider's interaction points. As in the case of accelerators with Siberian snakes, the spin tune is energy independent but is equal to zero instead of one half. The figure-8 topology eliminates the effect of arcs on the spin motion. There appears a unique opportunity to control the polarization of any particle species including deuterons, using longitudinal fields of small integrated strength (weak solenoids). Contrary to existing schemes, using weak solenoids in figure-8 colliders, one can control the polarization at the interaction points without essentially any effect on the beam's orbital characteristics. A universal scheme for control of the polarization using weak solenoids provides an elegant solution to the problem of ion acceleration completely eliminating resonant beam depolarization. It...
Wrong way recollement for schemes
Jorgensen, Peter
2005-01-01
A recollement of triangulated categories makes it possible to view one such category as being glued together from two others. The prototypical example is that D(X), a suitable derived category of sheaves on the topological space X, has a recollement in terms of D(Z) and D(U) when Z is a closed subset of X and U is the open complement. This note gives a different, "wrong way" recollement in the scheme case.
Parabolic sheaves on logarithmic schemes
Borne, Niels; Vistoli, Angelo
2010-01-01
We show how the natural context for the definition of parabolic sheaves on a scheme is that of logarithmic geometry. The key point is a reformulation of the concept of logarithmic structure in the language of symmetric monoidal categories, which might be of independent interest. Our main result states that parabolic sheaves can be interpreted as quasi-coherent sheaves on certain stacks of roots.
Trial of car-sharing scheme at CERN
Maximilien Brice
2010-01-01
On 6 July, a sample group of approximately 500 users started a six-month trial of a new car-sharing scheme. The project is an initiative of the General Infrastructure Services Department (GS), in collaboration with the Physics Department (PH) and Hertz car rentals.
Evaluation of Scheme Design of Blast Furnace Based on Artificial Neural Network
TANG Hong; LI Jing-min; YAO Bi-qiang; LIAO Hong-fu; YAO Jin
2008-01-01
Blast furnace scheme design is very important, since it directly affects the performance, cost and configuration of the blast furnace. An evaluation approach to furnace scheme design was brought forward based on artificial neural network. Ten independent parameters which determined a scheme design were proposed. The improved threelayer BP network algorithm was used to build the evaluation model in which the 10 independent parameters were taken as input evaluation indexes and the degree to which the scheme design satisfies the requirements of the blast furnace as output. It was trained by the existing samples of the scheme design and the experts' experience, and then tested by the other samples so as to develop the evaluation model. As an example, it is found that a good scheme design of blast furnace can be chosen by using the evaluation model proposed.
Mohammad Al-Fayoumi
2010-05-01
Full Text Available E-payment is now one of the most central research areas in e-commerce, mainly regarding online and offline payment scenarios. Customers are generally passive in e-commerce transaction. Relied on a blind signature, this paper introduces an e-payment protocol, in which customers have more initiative, and can terminate the transaction before possible cheats, its security is enhanced. Moreover, the cost of workers and communications falls down considerably while the cost of trusted authority and protecting information is increased. As there is no trusted authority in the proposed scheme, network overcrowding and conspiracy problems can be avoided. Furthermore, the protocol satisfies fairness and non-repudiation. This helps merchant and bank to speed up the financial transaction process and to give user instant services at any time. Also, in this paper, we will discuss an important e-payment protocol namely pay-word scheme and examine its advantages and limitations, which encourages the authors to improve the scheme that keeps all characteristics intact without compromise of the security robustness. The suggested protocol employs the idea of blind signature with the thought of hash chain. We will compare the proposed protocol with pay-word protocol and demonstrate that the proposed protocol offers more security and efficiency, which makes the protocol workable for real world services.
Cambridge community Optometry Glaucoma Scheme.
Keenan, Jonathan; Shahid, Humma; Bourne, Rupert R; White, Andrew J; Martin, Keith R
2015-04-01
With a higher life expectancy, there is an increased demand for hospital glaucoma services in the United Kingdom. The Cambridge community Optometry Glaucoma Scheme (COGS) was initiated in 2010, where new referrals for suspected glaucoma are evaluated by community optometrists with a special interest in glaucoma, with virtual electronic review and validation by a consultant ophthalmologist with special interest in glaucoma. 1733 patients were evaluated by this scheme between 2010 and 2013. Clinical assessment is performed by the optometrist at a remote site. Goldmann applanation tonometry, pachymetry, monoscopic colour optic disc photographs and automated Humphrey visual field testing are performed. A clinical decision is made as to whether a patient has glaucoma or is a suspect, and referred on or discharged as a false positive referral. The clinical findings, optic disc photographs and visual field test results are transmitted electronically for virtual review by a consultant ophthalmologist. The number of false positive referrals from initial referral into the scheme. Of the patients, 46.6% were discharged at assessment and a further 5.7% were discharged following virtual review. Of the patients initially discharged, 2.8% were recalled following virtual review. Following assessment at the hospital, a further 10.5% were discharged after a single visit. The COGS community-based glaucoma screening programme is a safe and effective way of evaluating glaucoma referrals in the community and reducing false-positive referrals for glaucoma into the hospital system. © 2014 Royal Australian and New Zealand College of Ophthalmologists.
A biometric signcryption scheme without bilinear pairing
Wang, Mingwen; Ren, Zhiyuan; Cai, Jun; Zheng, Wentao
2013-03-01
How to apply the entropy in biometrics into the encryption and remote authentication schemes to simplify the management of keys is a hot research area. Utilizing Dodis's fuzzy extractor method and Liu's original signcryption scheme, a biometric identity based signcryption scheme is proposed in this paper. The proposed scheme is more efficient than most of the previous proposed biometric signcryption schemes for that it does not need bilinear pairing computation and modular exponentiation computation which is time consuming largely. The analysis results show that under the CDH and DL hard problem assumption, the proposed scheme has the features of confidentiality and unforgeability simultaneously.
Design of Infusion Schemes for Neuroreceptor Imaging
Feng, Ling; Svarer, Claus; Madsen, Karine;
2016-01-01
for bolus infusion (BI) or programmed infusion (PI) experiments. Steady-state quantitative measurements can be made with one short scan and venous blood samples. The GABAA receptor ligand [(11)C]Flumazenil (FMZ) was chosen for this purpose, as it lacks a suitable reference region. Methods. Five bolus [(11)C......]FMZ-PET scans were conducted, based on which population-based PI and BI schemes were designed and tested in five additional healthy subjects. The design of a PI was assisted by an offline feedback controller. Results. The system could reproduce the measurements in blood and brain. With PI, [(11)C]FMZ steady...... state was attained within 40 min, which was 8 min earlier than the optimal BI (B/I ratio = 55 min). Conclusions. The system can design both BI and PI schemes to attain steady state rapidly. For example, subjects can be [(11)C]FMZ-PET scanned after 40 min of tracer infusion for 40 min with venous...
A random spatial sampling method in a rural developing nation
Michelle C. Kondo; Kent D.W. Bream; Frances K. Barg; Charles C. Branas
2014-01-01
Nonrandom sampling of populations in developing nations has limitations and can inaccurately estimate health phenomena, especially among hard-to-reach populations such as rural residents. However, random sampling of rural populations in developing nations can be challenged by incomplete enumeration of the base population. We describe a stratified random sampling method...
Lee, Ji-Sung; Kim, Jaiyong; Baik, Sei-Hyun; Park, Ie-Byung; Lee, Juneyoung
2009-03-01
An appropriate sampling strategy for estimating an epidemiologic volume of diabetes has been evaluated through a simulation. We analyzed about 250 million medical insurance claims data submitted to the Health Insurance Review & Assessment Service with diabetes as principal or subsequent diagnoses, more than or equal to once per year, in 2003. The database was re-constructed to a 'patient-hospital profile' that had 3,676,164 cases, and then to a 'patient profile' that consisted of 2,412,082 observations. The patient profile data was then used to test the validity of a proposed sampling frame and methods of sampling to develop diabetic-related epidemiologic indices. Simulation study showed that a use of a stratified two-stage cluster sampling design with a total sample size of 4,000 will provide an estimate of 57.04% (95% prediction range, 49.83 - 64.24%) for a treatment prescription rate of diabetes. The proposed sampling design consists, at first, stratifying the area of the nation into "metropolitan/city/county" and the types of hospital into "tertiary/secondary/primary/clinic" with a proportion of 5:10:10:75. Hospitals were then randomly selected within the strata as a primary sampling unit, followed by a random selection of patients within the hospitals as a secondly sampling unit. The difference between the estimate and the parameter value was projected to be less than 0.3%. The sampling scheme proposed will be applied to a subsequent nationwide field survey not only for estimating the epidemiologic volume of diabetes but also for assessing the present status of nationwide diabetes control.
[Individualized, personalized and stratified medicine: a challenge for allergology in ENT?].
Chaker, Adam M; Klimek, L
2015-05-01
Individualized, personalized or stratified medicine approaches offer emerging opportunities in the field of allergy and ENT. Avoidance of side effects, targeted therapy approaches and stratified prevention promise better outcomes and optimal results for patients. Conceptual incongruencies remain with regard to definitions and perceptions of "personalized medicine". Serious ethical considerations have to be taken into account. The development of pharmacogenomics, molecular phenotyping, genomic sequencing and other -omics opens the door to unique mechanistic therapeutic advances. The molecular allergology and recombinant diagnostics available are tools that offer substantial improved diagnostics for the benefit of allergic patients, e. g. in anaphylaxis and food allergy. For stratified therapeutic approaches, however, regulatory affairs will have to keep pace with medical and scientific discovery.
A dynamic subgrid-scale model for the large eddy simulation of stratified flow
刘宁宇; 陆夕云; 庄礼贤
2000-01-01
A new dynamic subgrid-scale (SGS) model, including subgrid turbulent stress and heat flux models for stratified shear flow is proposed by using Yoshizawa’ s eddy viscosity model as a base model. Based on our calculated results, the dynamic subgrid-scale model developed here is effective for the large eddy simulation (LES) of stratified turbulent channel flows. The new SGS model is then applied to the large eddy simulation of stratified turbulent channel flow under gravity to investigate the coupled shear and buoyancy effects on the near-wall turbulent statistics and the turbulent heat transfer at different Richardson numbers. The critical Richardson number predicted by the present calculation is in good agreement with the value of theoretical analysis.
A dynamic subgrid-scale model for the large eddy simulation of stratified flow
无
2000-01-01
A new dynamic subgrid-scale (SGS) model, including subgrid turbulent stress and heat flux models for stratified shear flow is proposed by using Yoshizawa's eddy viscosity model as a base model. Based on our calculated results, the dynamic subgrid-scale model developed here is effective for the large eddy simulation (LES) of stratified turbulent channel flows. The new SGS model is then applied to the large eddy simulation of stratified turbulent channel flow under gravity to investigate the coupled shear and buoyancy effects on the near-wall turbulent statistics and the turbulent heat transfer at different Richardson numbers. The critical Richardson number predicted by the present calculation is in good agreement with the value of theoretical analysis.
A criterion for the onset of slugging in horizontal stratified air-water countercurrent flow
Chun, Moon-Hyun; Lee, Byung-Ryung; Kim, Yang-Seok [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)] [and others
1995-09-01
This paper presents an experimental and theoretical investigation of wave height and transition criterion from wavy to slug flow in horizontal air-water countercurrent stratified flow conditions. A theoretical formula for the wave height in a stratified wavy flow regime has been developed using the concept of total energy balance over a wave crest to consider the shear stress acting on the interface of two fluids. From the limiting condition of the formula for the wave height, a necessary criterion for transition from a stratified wavy flow to a slug flow has been derived. A series of experiments have been conducted changing the non-dimensional water depth and the flow rates of air in a horizontal pipe and a duct. Comparisons between the measured data and the predictions of the present theory show that the agreement is within {plus_minus}8%.
Effect of turbulent fluctuations on the behaviour of fountains in stratified environments
Freire, D.; Cabeza, C.; Pauletti, S.; Sarasúa, G.; Bove, I.; Usera, G.; Martí, A. C.
2010-09-01
The interaction between a turbulent fountain and its stratified environment was studied. A heavy fluid, cold water, was injected vertically upwards into a linearly stratified medium. The round heavy-fluid jet reaches a maximum height before it begins to fall due to the effect of gravity. Because of the effects of friction and mixing, the vertical momentum and density of the jet fluid decrease as it submerges to an intermediate height of zero buoyancy. At this point, the jet fluid spreads as a horizontal front, intruding into the stratified environment. The degree of fluctuation in the proximity of the injection point was studied under both unrestricted- and restricted-flow configurations at the injection, using two differently sized stainless-steel woven-wire screens at the injection port as flow-restricting means. Using visualization and velocimetry techniques, both maximum and spreading heights were found to decrease with increasing turbulence at the point of injection.
Third Annual Open Meeting of the UK Pharmacogenomics and Stratified Medicine Network Conference.
Bradshaw, Elizabeth H
2015-07-01
Third Annual Open Meeting of the UK Pharmacogenetics and Stratified Medicine Network 14 January 2015, Wellcome Trust Genome Campus, Hinxton, Cambridge, UK The third Annual Open Meeting of the UK Pharmacogenetics and Stratified Medicine Network was held on 14 January 2015 in association with the Wellcome Trust on the Wellcome Trust Genome Campus at Hinxton, Cambridge, UK. In the morning, speakers from Cancer Research UK, the Medical Research Council, Genomics England, Innovate UK (formerly TSB) and the Department of Health described the current major projects they are funding. In the afternoon, speakers from various universities around the United Kingdom presented data on pharmacogenetics and stratified medicine research covering diverse disease areas including cancers, warfarin dosing, Gaucher disease and rheumatoid arthritis.
Convective heat transport in stratified atmospheres at low and high Mach number
Anders, Evan H
2016-01-01
Convection in astrophysical systems is stratified and often occurs at high Rayleigh number (Ra) and low Mach number (Ma). Here we study stratified convection in the context of plane-parallel, polytropically stratified atmospheres. We hold the density stratification ($n_{\\rho}$) and Prandtl number (Pr) constant while varying Ma and Ra to determine the behavior of the Nusselt number (Nu), which quantifies the efficiency of convective heat transport. As Ra increases and $\\text{Ma} \\rightarrow 1$, a scaling of Nu $\\propto$ Ra$^{0.45}$ is observed. As Ra increases to a regime where Ma $\\geq 1$, this scaling gives way to a weaker Nu $\\propto$ Ra$^{0.19}$. In the regime of Ma $\\ll 1$, a consistent Nu $\\propto$ Ra$^{0.31}$ is retrieved, reminiscent of the Nu $\\propto$ Ra$^{2/7}$ seen in Rayleigh-B\\'{e}nard convection.
Prediction of Stratified Flow Temperature Profiles in a Fully Insulated Environment
Ahmad S. Awad
2014-07-01
Full Text Available The aim of the study is to present an analytical model to predict the temperature profiles in thermal stratified environment. Thermal stratification is encountered in many situations. The flow of contaminants and hydrocarbons in environment often get stratified. The prediction of temperature profiles and flow characteristics are essential for HVAC applications, environment and energy management. The temperature profiles in the stratified region are successfully obtained, in terms of flow-operating functions. The analytical model agrees well with the published experimental data as well as the related closed-form solutions, which is helpful for HVAC applications. The model will be further developed and incorporated within a numerical model in order to investigate the flow field characteristics and establish correlations for a wide range of parameters.
Abdullah Ahmed Foisal
2016-01-01
Full Text Available MHD free convection over an inclined plate in a thermally stratified high porous medium in the presence of a magnetic field has been studied. The dimensionless momentum and temperature equations have been solved numerically by explicit finite difference technique with the help of a computer programming language Compaq Visual Fortran 6.6a. The obtained results of these studies have been discussed for the different values of well known parameters with different time steps. Also, the stability conditions and convergence criteria of the explicit finite difference scheme has been analyzed for finding the restriction of the values of various parameters to get more accuracy. The effects of various governing parameters on the fluid velocity, temperature, local and average shear stress and Nusselt number has been investigated and presented graphically.
Sample size estimation and sampling techniques for selecting a representative sample
Aamir Omair
2014-01-01
Full Text Available Introduction: The purpose of this article is to provide a general understanding of the concepts of sampling as applied to health-related research. Sample Size Estimation: It is important to select a representative sample in quantitative research in order to be able to generalize the results to the target population. The sample should be of the required sample size and must be selected using an appropriate probability sampling technique. There are many hidden biases which can adversely affect the outcome of the study. Important factors to consider for estimating the sample size include the size of the study population, confidence level, expected proportion of the outcome variable (for categorical variables/standard deviation of the outcome variable (for numerical variables, and the required precision (margin of accuracy from the study. The more the precision required, the greater is the required sample size. Sampling Techniques: The probability sampling techniques applied for health related research include simple random sampling, systematic random sampling, stratified random sampling, cluster sampling, and multistage sampling. These are more recommended than the nonprobability sampling techniques, because the results of the study can be generalized to the target population.
Towards Cost-efficient Sampling Methods
Peng, Luo; Chong, Wu
2014-01-01
The sampling method has been paid much attention in the field of complex network in general and statistical physics in particular. This paper presents two new sampling methods based on the perspective that a small part of vertices with high node degree can possess the most structure information of a network. The two proposed sampling methods are efficient in sampling the nodes with high degree. The first new sampling method is improved on the basis of the stratified random sampling method and selects the high degree nodes with higher probability by classifying the nodes according to their degree distribution. The second sampling method improves the existing snowball sampling method so that it enables to sample the targeted nodes selectively in every sampling step. Besides, the two proposed sampling methods not only sample the nodes but also pick the edges directly connected to these nodes. In order to demonstrate the two methods' availability and accuracy, we compare them with the existing sampling methods in...
Kernel machine testing for risk prediction with stratified case cohort studies.
Payne, Rebecca; Neykov, Matey; Jensen, Majken Karoline; Cai, Tianxi
2016-06-01
Large assembled cohorts with banked biospecimens offer valuable opportunities to identify novel markers for risk prediction. When the outcome of interest is rare, an effective strategy to conserve limited biological resources while maintaining reasonable statistical power is the case cohort (CCH) sampling design, in which expensive markers are measured on a subset of cases and controls. However, the CCH design introduces significant analytical complexity due to outcome-dependent, finite-population sampling. Current methods for analyzing CCH studies focus primarily on the estimation of simple survival models with linear effects; testing and estimation procedures that can efficiently capture complex non-linear marker effects for CCH data remain elusive. In this article, we propose inverse probability weighted (IPW) variance component type tests for identifying important marker sets through a Cox proportional hazards kernel machine (CoxKM) regression framework previously considered for full cohort studies (Cai et al., 2011). The optimal choice of kernel, while vitally important to attain high power, is typically unknown for a given dataset. Thus, we also develop robust testing procedures that adaptively combine information from multiple kernels. The proposed IPW test statistics have complex null distributions that cannot easily be approximated explicitly. Furthermore, due to the correlation induced by CCH sampling, standard resampling methods such as the bootstrap fail to approximate the distribution correctly. We, therefore, propose a novel perturbation resampling scheme that can effectively recover the induced correlation structure. Results from extensive simulation studies suggest that the proposed IPW CoxKM testing procedures work well in finite samples. The proposed methods are further illustrated by application to a Danish CCH study of Apolipoprotein C-III markers on the risk of coronary heart disease. © 2015, The International Biometric Society.
Behtani, A.; Bouazzouni, A.; Khatir, S.; Tiachacht, S.; Zhou, Y.-L.; Abdel Wahab, M.
2017-05-01
In this paper, the problem of using measured modal parameters to detect and locate damage in beam composite stratified structures with four layers of graphite/epoxy [0°/902°/0°] is investigated. A technique based on the residual force method is applied to composite stratified structure with different boundary conditions, the results of damage detection for several damage cases demonstrate that using residual force method as damage index, the damage location can be identified correctly and the damage extents can be estimated as well.
Algebraic K-theory of generalized schemes
Anevski, Stella Victoria Desiree
Nikolai Durov has developed a generalization of conventional scheme theory in which commutative algebraic monads replace commutative unital rings as the basic algebraic objects. The resulting geometry is expressive enough to encompass conventional scheme theory, tropical algebraic geometry...
Wireless Broadband Access and Accounting Schemes
无
2003-01-01
In this paper, we propose two wireless broadband access and accounting schemes. In both schemes, the accounting system adopts RADIUS protocol, but the access system adopts SSH and SSL protocols respectively.
Elliptic Curve Blind Digital Signature Schemes
YOULin; YANGYixian; WENQiaoyan
2003-01-01
Blind signature schemes are important cryptographic protocols in guaranteeing the privacy or anonymity of the users.Three new blind signature schemes and their corresponding generalizations are pro-posed. Moreover, their securities are simply analyzed.
Algebraic K-theory of generalized schemes
Anevski, Stella Victoria Desiree
Nikolai Durov has developed a generalization of conventional scheme theory in which commutative algebraic monads replace commutative unital rings as the basic algebraic objects. The resulting geometry is expressive enough to encompass conventional scheme theory, tropical algebraic geometry...
Secret sharing scheme with inherited characteristic
Ye Zhenjun; Meng Fanzhen
2006-01-01
To assure the shareholders can look for their "legal" attorneys to renew the secret, once the secret sharing scheme is initialized, a secret sharing scheme with inherited characteristic is constructed. In this scheme, each shareholder can produce a new share by his algorithm, which is equivalent to the primary one. Together with other shares, the primary secret can be renewed. Since this scheme is constructed not by replacing the primary share with a new share produced by the dealer in his primitive secret sharing scheme, so no matter how much shares the shareholder produces, these shares can not be gathered together to renew the secret in this scheme. Compared with the existing secret sharing schemes, this scheme provides more agility for the shareholders by investing each of them a function but not affect its security.
Seyfert Galaxies: Radio Continuum Emission Properties and the Unification Scheme
Veeresh Singh; Prajval Shastri; Ramana Athreya
2011-12-01
Seyfert galaxies are classified mainly into type 1 and type 2 depending on the presence and absence of broad permitted emission lines in their optical spectra, respectively. Unification scheme hypothesizes that the observed similarities and differences between the two Seyfert subtypes can be understood as due to the differing orientations of anisotropically distributed obscuring material having a torus-like geometry around the AGN. We investigate the radio continuum emission properties of a sample of Seyfert galaxies in the framework of the unification scheme.
Task analysis of laparoscopic camera control schemes.
Ellis, R Darin; Munaco, Anthony J; Reisner, Luke A; Klein, Michael D; Composto, Anthony M; Pandya, Abhilash K; King, Brady W
2016-12-01
Minimally invasive surgeries rely on laparoscopic camera views to guide the procedure. Traditionally, an expert surgical assistant operates the camera. In some cases, a robotic system is used to help position the camera, but the surgeon is required to direct all movements of the system. Some prior research has focused on developing automated robotic camera control systems, but that work has been limited to rudimentary control schemes due to a lack of understanding of how the camera should be moved for different surgical tasks. This research used task analysis with a sample of eight expert surgeons to discover and document several salient methods of camera control and their related task contexts. Desired camera placements and behaviours were established for two common surgical subtasks (suturing and knot tying). The results can be used to develop better robotic control algorithms that will be more responsive to surgeons' needs. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
Linear multi-secret sharing schemes
XIAO Liangliang; LIU Mulan
2005-01-01
In this paper the linear multi-secret sharing schemes are studied by using monotone span programs. A relation between computing monotone Boolean functions by using monotone span programs and realizing multi-access structures by using linear multisecret sharing schemes is shown. Furthermore, the concept of optimal linear multi-secret sharing scheme is presented and the several schemes are proved to be optimal.
Improvement of publicly verifiable authenticated encryption scheme
LEI Fei-yu; CHEN Wen; MA Chang-she; CHEN Ke-fei
2007-01-01
A weakness of unforgeability is found in Ma and Chen scheme, and the root cause is the susceptive linear design in the scheme. In order to avoid the weakness and susceptive linear design, an improvement by means of two mechanisms including quadratic residue and composite discrete logarithm is proposed, which can defeat the forgery attacks in Ma and Chen scheme. The new scheme remains good confidentiality, public verifiability and efficiency.
A massive momentum-subtraction scheme
Boyle, Peter; Khamseh, Ava
2016-01-01
A new renormalization scheme is defined for fermion bilinears in QCD at non vanishing quark masses. This new scheme, denoted RI/mSMOM, preserves the benefits of the nonexceptional momenta introduced in the RI/SMOM scheme, and allows a definition of renormalized composite fields away from the chiral limit. Some properties of the scheme are investigated by performing explicit one-loop computation in dimensional regularization.
MIRD radionuclide data and decay schemes
Eckerman, Keith F
2007-01-01
For all physicians, scientists, and physicists working in the nuclear medicine field, the MIRD: Radionuclide Data and Decay Schemes updated edition is an essential sourcebook for radiation dosimetry and understanding the properties of radionuclides. Includes CD Table of Contents Decay schemes listed by atomic number Radioactive decay processes Serial decay schemes Decay schemes and decay tables This essential reference for nuclear medicine physicians, scientists and physicists also includes a CD with tabulations of the radionuclide data necessary for dosimetry calculations.
Comparative study of numerical schemes of TVD3, UNO3-ACM and optimized compact scheme
Lee, Duck-Joo; Hwang, Chang-Jeon; Ko, Duck-Kon; Kim, Jae-Wook
1995-01-01
Three different schemes are employed to solve the benchmark problem. The first one is a conventional TVD-MUSCL (Monotone Upwind Schemes for Conservation Laws) scheme. The second scheme is a UNO3-ACM (Uniformly Non-Oscillatory Artificial Compression Method) scheme. The third scheme is an optimized compact finite difference scheme modified by us: the 4th order Runge Kutta time stepping, the 4th order pentadiagonal compact spatial discretization with the maximum resolution characteristics. The problems of category 1 are solved by using the second (UNO3-ACM) and third (Optimized Compact) schemes. The problems of category 2 are solved by using the first (TVD3) and second (UNO3-ACM) schemes. The problem of category 5 is solved by using the first (TVD3) scheme. It can be concluded from the present calculations that the Optimized Compact scheme and the UN03-ACM show good resolutions for category 1 and category 2 respectively.
Population Monotonic Path Schemes for Simple Games
Ciftci, B.B.; Borm, P.E.M.; Hamers, H.J.M.
2006-01-01
A path scheme for a simple game is composed of a path, i.e., a sequence of coalitions that is formed during the coalition formation process and a scheme, i.e., a payoff vector for each coalition in the path.A path scheme is called population monotonic if a player's payoff does not decrease as the pa
A new semi-Lagrangian difference scheme
季仲贞; 陈嘉滨
2001-01-01
A new completely energy-conserving semi-Lagrangian scheme is constructed. The numerical solution of shallow water equation shows that this conservative scheme preserves the total energy in twelve significant digits, while the traditional scheme does only in five significant digits.
Arbitrated quantum signature scheme with message recovery
Lee, Hwayean; Hong, Changho; Kim, Hyunsang; Lim, Jongin; Yang, Hyung Jin
2004-02-16
Two quantum signature schemes with message recovery relying on the availability of an arbitrator are proposed. One scheme uses a public board and the other does not. However both schemes provide confidentiality of the message and a higher efficiency in transmission.
Quantum Signature Scheme with Weak Arbitrator
Luo, Ming-Xing; Chen, Xiu-Bo; Yun, Deng; Yang, Yi-Xian
2012-07-01
In this paper, we propose one quantum signature scheme with a weak arbitrator to sign classical messages. This scheme can preserve the merits in the original arbitrated scheme with some entanglement resources, and provide a higher efficiency in transmission and reduction the complexity of implementation. The arbitrator is costless and only involved in the disagreement case.
Current terminology and diagnostic classification schemes.
Okeson, J P
1997-01-01
This article reviews the current terminology and classification schemes available for temporomandibular disorders. The origin of each term is presented, and the classification schemes that have been offered for temporomandibular disorders are briefly reviewed. Several important classifications are presented in more detail, with mention of advantages and disadvantages. Final recommendations are provided for future direction in the area of classification schemes.
A Model of Hierarchical Key Assignment Scheme
ZHANG Zhigang; ZHAO Jing; XU Maozhi
2006-01-01
A model of the hierarchical key assignment scheme is approached in this paper, which can be used with any cryptography algorithm. Besides, the optimal dynamic control property of a hierarchical key assignment scheme will be defined in this paper. Also, our scheme model will meet this property.
Support Schemes and Ownership Structures
Ropenus, Stephanie; Schröder, Sascha Thorsten; Costa, Ana
In recent years, fuel cell based micro‐combined heat and power has received increasing attention due to its potential contribution to energy savings, efficiency gains, customer proximity and flexibility in operation and capacity size. The FC4Home project assesses technical and economic aspects...... for promoting combined heat and power and energy from renewable sources. These Directives are to be implemented at the national level by the Member States. Section 3 conceptually presents the spectrum of national support schemes, ranging from investment support to market‐based operational support. The choice...
Banks, Tom; Torres, T. J.
2012-10-01
We summarize recent work in which we attempt to make consistent models of LHC physics, from the Pyramid Scheme. The models share much with the NMSSM, in particular, enhanced tree level contributions to the Higgs mass and a preference for small tan β. There are three different singlet fields, and a new strongly coupled gauge theory, so the constraints of perturbative unification are quite different. We outline our general approach to the model, which contains a Kähler potential for three of the low energy fields, which is hard to calculate. Detailed calculations, based on approximations to the Kähler potential, will be presented in a future publication.
Trisjono, Philipp; Kang, Seongwon; Pitsch, Heinz
2016-12-01
The main objective of this study is to present an accurate and consistent numerical framework for turbulent reacting flows based on a high-order finite difference (HOFD) scheme. It was shown previously by Desjardins et al. (2008) [4] that a centered finite difference scheme discretely conserving the kinetic energy and an upwind-biased scheme for the scalar transport can be combined into a useful scheme for turbulent reacting flows. With a high-order spatial accuracy, however, an inconsistency among discretization schemes for different conservation laws is identified, which can disturb a scalar field spuriously under non-uniform density distribution. Various theoretical and numerical analyses are performed on the sources of the unphysical error. From this, the derivative of the mass-conserving velocity and the local Péclet number are identified as the primary factors affecting the error. As a solution, an HOFD stencil for the mass conservation is reformulated into a flux-based form that can be used consistently with an upwind-biased scheme for the scalar transport. The effectiveness of the proposed formulation is verified using two-dimensional laminar flows such as a scalar transport problem and a laminar premixed flame, where unphysical oscillations in the scalar fields are removed. The applicability of the proposed scheme is demonstrated in an LES of a turbulent stratified premixed flame.
Ju, Cheng; Liu, Na; Wang, Dongdong; Zhang, Zhiguo; Chen, Xue
2016-11-01
Scalable transmitter frontend scheme is proposed to reduce the sampling rate of digital-to-analog converter (DAC) and the complexity of digital signal processing (DSP) in intensity modulation and direct detection (IMDD) OFDMA-PON upstream scenarios. The hardware cost of each ONU is substantially decreased. The feasibility of the proposed scheme is experimentally demonstrated.
Javid Shabbir
2012-01-01
Full Text Available In this paper we propose a combined exponential ratio type estimator of finite population mean utilizing information on the auxiliary attribute(s under non-response. Expressions for bias and MSE of the proposed estimator are derived up to first order of approximation. An empirical study is carried out to observe the performances of the estimators.
Yungang He; Shuhua Xu; Chuan Jia; Li Jin
2009-01-01
@@ Dear Editors, More and more genetic variants which contribute to human complex traits were identified recently in genome-wide association studies (GWAS), an approach that shows more efficiency than any other genetic ap-proaches ever before [1].It holds the promise to disclose genetic mechanism underlying the mystery of human diseases, since the most, if not all, of the genetic variants in the human genome could be investigated for their pos-sible association with diseases by comparing the frequen-cies of alleles in the cases (patients) and controls (healthy subjects).
REMINDER: Saved Leave Scheme (SLS)
2003-01-01
Transfer of leave to saved leave accounts Under the provisions of the voluntary saved leave scheme (SLS), a maximum total of 10 days'* annual and compensatory leave (excluding saved leave accumulated in accordance with the provisions of Administrative Circular No 22B) can be transferred to the saved leave account at the end of the leave year (30 September). We remind you that unused leave of all those taking part in the saved leave scheme at the closure of the leave year accounts is transferred automatically to the saved leave account on that date. Therefore, staff members have no administrative steps to take. In addition, the transfer, which eliminates the risk of omitting to request leave transfers and rules out calculation errors in transfer requests, will be clearly shown in the list of leave transactions that can be consulted in EDH from October 2003 onwards. Furthermore, this automatic leave transfer optimizes staff members' chances of benefiting from a saved leave bonus provided that they ar...
Sjoberg, Daniel
2008-01-01
This paper presents an overview of how circuit models can be used for analysing wave propagation in stratified structures. Relatively complex structures can be analysed using models which are accessible to undergraduate students. Homogeneous slabs are modelled as transmission lines, and thin sheets between the slabs are modelled as lumped…
Leung, Chi-Keung; Chang, Hua-Hua; Hau, Kit-Tai
The multistage alpha-stratified computerized adaptive testing (CAT) design advocated a new philosophy of pool management and item selection using low discriminating items first. It has been demonstrated through simulation studies to be effective both in reducing item overlap rate and enhancing pool utilization with certain pool types. Based on…
Experimental investigation on isothermal stratified flow mixing in a horizontal T-junction
Isaev, Alexander; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. fuer Kernenergetik und Energiesysteme (IKE)
2016-10-15
Turbulent and stratified flows can lead to thermal fatigue in piping systems of nuclear power plants (NPP). Such flows can be investigated in the University of Stuttgart Fluid-Structure-Interaction (FSI) facility with a T-Junction at thermal conditions with temperature differences of up to 255 K and at pressures of maximum 75 bars.
Analysing stratified medicine business models and value systems: innovation-regulation interactions.
Mittra, James; Tait, Joyce
2012-09-15
Stratified medicine offers both opportunities and challenges to the conventional business models that drive pharmaceutical R&D. Given the increasingly unsustainable blockbuster model of drug development, due in part to maturing product pipelines, alongside increasing demands from regulators, healthcare providers and patients for higher standards of safety, efficacy and cost-effectiveness of new therapies, stratified medicine promises a range of benefits to pharmaceutical and diagnostic firms as well as healthcare providers and patients. However, the transition from 'blockbusters' to what might now be termed 'niche-busters' will require the adoption of new, innovative business models, the identification of different and perhaps novel types of value along the R&D pathway, and a smarter approach to regulation to facilitate innovation in this area. In this paper we apply the Innogen Centre's interdisciplinary ALSIS methodology, which we have developed for the analysis of life science innovation systems in contexts where the value creation process is lengthy, expensive and highly uncertain, to this emerging field of stratified medicine. In doing so, we consider the complex collaboration, timing, coordination and regulatory interactions that shape business models, value chains and value systems relevant to stratified medicine. More specifically, we explore in some depth two convergence models for co-development of a therapy and diagnostic before market authorisation, highlighting the regulatory requirements and policy initiatives within the broader value system environment that have a key role in determining the probable success and sustainability of these models.
Sjoberg, Daniel
2008-01-01
This paper presents an overview of how circuit models can be used for analysing wave propagation in stratified structures. Relatively complex structures can be analysed using models which are accessible to undergraduate students. Homogeneous slabs are modelled as transmission lines, and thin sheets between the slabs are modelled as lumped…
"Being" Black and Strategizing for Excellence in a Racially Stratified Academic Hierarchy
O'Connor, Carla; Mueller, Jennifer; Lewis, R. L'Heureux; Rivas-Drake, Deborah; Rosenberg, Seneca
2011-01-01
This article reports the findings of an ethnographic study of Black identity and achievement in one predominantly White high school featuring a racially stratified academic hierarchy (RSAH). Foregrounding the experiences of three exceptionally achieving Black girls against those of other high-achieving but less stellar students, the study…
van Aartrijk, M.; Clercx, H.J.H.
2010-01-01
The dispersion of light inertial particles $\\rho_p/\\rho_f = \\mathcal{O}(1)$ in statistically stationary stably stratified turbulence is studied by means of direct numerical simulations. The light particle dispersion behavior is found to be comparable to that of heavy particles when displayed as a
Stratified Flow in a Room with Displacement Ventilation and Wall-Mounted Air Terminal devices
Nielsen, Peter V.
This paper describes experiments with wall-mounted air terminal devices. The stratified flow in the room is analyzed, and the influence of stratification and the influence of room dimensions on the velocity level and on the length scale are proved. The velocity level in the occupied zone can be d...
Carmo, Carolina; Dumont, Olivier; Nielsen, Mads Pagh
2015-01-01
coupled with energy system solutions is limited. In this poster, a discretized model of a stratified tank developed in Modelica is presented. The physical phenoma to be considered are the thermal transfers by conduction and convection – stratification, heat loss to ambient, charging and discharging...
Deal, J. H.
1975-01-01
One approach to the problem of simplifying complex nonlinear filtering algorithms is through using stratified probability approximations where the continuous probability density functions of certain random variables are represented by discrete mass approximations. This technique is developed in this paper and used to simplify the filtering algorithms developed for the optimum receiver for signals corrupted by both additive and multiplicative noise.
Modified Limiting Equilibrium Method for Stability Analysis of Stratified Rock Slopes
Rui Yong
2016-01-01
Full Text Available The stratified rock of Jurassic strata is widely distributed in Three Gorges Reservoir Region. The limit equilibrium method is generally utilized in the stability analysis of rock slope with single failure plane. However, the stratified rock slope cannot be accurately estimated by this method because of different bedding planes and their variable shear strength parameters. Based on the idealized model of rock slope with bedding planes, a modified limiting equilibrium method is presented to determine the potential sliding surface and the factor of safety for the stratified rock slope. In this method, the S-curve model is established to define the spatial variations of the shear strength parameters c and φ of bedding plane and the tensile strength of rock mass. This method was applied in the stability evaluation of typical stratified rock slope in Three Gorges Reservoir Region, China. The result shows that the factor of safety of the case study is 0.973, the critical sliding surface for the potential slip surface appears at bedding plane C, and the tension-controlled failure occurs at 10.5 m to the slope face.
Study on Reform of College English Stratified Teaching Based on School-Based Characteristics
Yang, Liu
2012-01-01
Considering the status quo of college English teaching, we implement stratified teaching, which reflects the idea of stratification in terms of teaching objects, teaching management, teaching process and assessment and evaluation, makes each students get development to the greatest extent in interactive teaching practice of teaching and learning…
Fabiano, B.; Kersten, R.J.A.; Opschoor, G.; Pastorino, R.
2002-01-01
The occurrence of a rapid phase transition, or so-called explosive boiling, when a cold volatile liquid comes into contact with a hot liquid or hot surface is a potential hazard in industry. This study was focused on the explosive boiling potential of thermally stratified liquid-liquid systems that
Measures to assess the prognostic ability of the stratified Cox proportional hazards model
(Tybjaerg-Hansen, A.) The Fibrinogen Studies Collaboration.The Copenhagen City Heart Study; Tybjærg-Hansen, Anne
2009-01-01
Many measures have been proposed to summarize the prognostic ability of the Cox proportional hazards (CPH) survival model, although none is universally accepted for general use. By contrast, little work has been done to summarize the prognostic ability of the stratified CPH model; such measures w...
Developing spatially stratified N{sub 2}O emission factors for Europe
Leip, Adrian, E-mail: adrian.leip@jrc.ec.europa.eu [European Commission-Joint Research Centre, Institute for Environment and Sustainability, Ispra (Italy); Busto, Mirko [International Institute for Applied Systems Analysis, Laxenburg (Austria); Winiwarter, Wilfried [International Institute for Applied Systems Analysis, Laxenburg (Austria); AIT Austrian Institute of Technology, Vienna (Austria)
2011-11-15
We investigate the possibility to replace the - so-called - Tier 1 IPCC approach to estimate soil N{sub 2}O emissions with stratified emissions factors that take into account both N-input and the spatial variability of the environmental conditions within the countries of the European Union, using the DNDC-Europe model. Spatial variability in model simulations is high and corresponds to the variability reported in literature for field data. Our results indicate that (a) much of the observed variability in N{sub 2}O fluxes reflects the response of soils to external conditions, (b) it is likely that national inventories tend to overestimate the uncertainties in their estimated direct N{sub 2}O emissions from arable soils; (c) on average over Europe, the fertilizer-induced emissions (FIE) coincide with the IPCC factors, but they display large spatial variations. Therefore, at scales of individual countries or smaller, a stratified approach considering fertilizer type, soil characteristics and climatic parameters is preferable. - Highlights: > Stratified modelling improves estimates of direct N2O emissions from arable soils. > Large variability between strata (expressed as countries) becomes evident. > Fertilizer-induced emissions of N{sub 2}O differ by N input (manure or mineral fertilizer). > National inventories likely overestimate the uncertainties for direct N2O emissions - Model simulations suggest that stratified country-specific N{sub 2}O emission factors are useful to better describe the soil emission behaviour of the European Union countries.
Masada, Youhei
2016-01-01
We report the first successful simulation of spontaneous formation of surface magnetic structures from a large-scale dynamo by strongly-stratified thermal convection in Cartesian geometry. The large-scale dynamo observed in our strongly-stratified model has physical properties similar to those in earlier weakly-stratified convective dynamo simulations, indicating that the $\\alpha^2$-type mechanism is responsible for it. Additionally to the large-scale dynamo, we find that large-scale structures of the vertical magnetic field are spontaneously formed in the convection zone surface only for the case of strongly-stratified atmosphere. The organization of the vertical magnetic field proceeds in the upper convection zone within tens of convective turn-over time and band-like bipolar structures are recurrently-appeared in the dynamo-saturated stage. We examine possibilities of several candidates as the origin of the surface magnetic structure formation, and then suggest the existence of an as-yet-unknown mechanism ...
ON THE EMBEDDING OF TOP IN THE CATEGORY OF STRATIFIED L-TOPOLOGICAL SPACES
LAI HONGLIANG; ZHANG DEXUE
2005-01-01
Let L be a meet continuous lattice. It is proved that the category Top of topological spaces can be embedded in the category of stratified L-topological spaces as a concretely both reflective and coreflective full subcategory if and only if L is a continuous lattice.
Computational Fluid Dynamics model of stratified atmospheric boundary-layer flow
Koblitz, Tilman; Bechmann, Andreas; Sogachev, Andrey;
2015-01-01
For wind resource assessment, the wind industry is increasingly relying on computational fluid dynamics models of the neutrally stratified surface-layer. So far, physical processes that are important to the whole atmospheric boundary-layer, such as the Coriolis effect, buoyancy forces and heat...
Coherence theory of electromagnetic wave propagation through stratified N-layer media
Hoenders, B.J.; Bertolotti, M.
The theory of second-order coherence in connection with wave propagation through a stratified N-layer (SNL) medium is developed. Especially, the influence of the SNL medium on the propagation of the coherence generated by a given state of coherence at the entrance plane of the medium is considered.
Seasonal cyclogenesis and the role of near-surface stratified layer in the Bay of Bengal
Murty, V.S.N.; Sarma, M.S.S.; Tilvi, V.
The role of the near-surface stratified layer developed due to the spread of low salinity waters under the influence of freshwater influx on the cyclogenesis over the Bay of Bengal is addressed. The seasonal variation of the Effective Oceanic Layer...
Tong, M.S.; Lu, Y.; Chen, Y.
2005-01-01
A planar stratified dielectric slab medium, which is an interesting problem in optics and geophysics, is studied using a pseudo-spectral time-domain (PSTD) algorithm. Time domain electric fields and frequency domain propagation characteristics of both single and periodic dielectric slab...
Pseudorandomness of Camellia-Like Scheme
Wen-Ling Wu
2006-01-01
Luby and Rackoff idealized DES by replacing each round function with one large random function. In this paper, the author idealizes Camellia by replacing each S-box with one small random function, which is named Camellialike scheme. It is then proved that five-round Camellia-like scheme is pseudorandom and eight-round Camellia-like scheme is super-pseudorandom for adaptive adversaries. Further the paper considers more efficient construction of Camellia-like scheme, and discusses how to construct pseudorandom Camellia-like scheme from less random functions.
Modification of QUICK scheme by skew points
Mirzaei, M.; Mohammadi, R.; Malekzadeh, M. [K.N. Toosi Univ. of Technology, Aerospace Engineering Dept., Tehran (Iran, Islamic Republic of)]. E-mail: Mirzaei@kntu.ac.ir
2005-07-01
This paper presents a new method for convective flux approximation based on inclusions of skew points. The scheme uses the truncated terms of QUICK scheme and with the aid of an equation extracted from momentum equations, the skew points will appear in the convective flux formula. The results show that the presented scheme has better accuracy than the other schemes. Diffusion fluxes are approximated using power law scheme and for evaluation of the performance of the presented method several test cases were carried out and the results are compared with the results of other numerical works and experimental data. (author)
A Provably Secure Asynchronous Proactive RSA Scheme
ZHANG Rui-shan; LI Qiang; CHEN Ke-fei
2005-01-01
The drawback of the first asynchronous proactive RSA scheme presented by Zhou in 2001, is that the se curity definition and security proof do not follow the approach of provable security. This paper presented a provably secure asynchronous proactive RSA scheme, which includes three protocols: initial key distribution protocol,signature generation protocol and share refreshing protocol. Taken these protocols together, a complete provably secure proactive RSA scheme was obtained. And the efficiency of the scheme is approximate to that of the scheme of Zhou.
Hash function based secret sharing scheme designs
Chum, Chi Sing
2011-01-01
Secret sharing schemes create an effective method to safeguard a secret by dividing it among several participants. By using hash functions and the herding hashes technique, we first set up a (t+1, n) threshold scheme which is perfect and ideal, and then extend it to schemes for any general access structure. The schemes can be further set up as proactive or verifiable if necessary. The setup and recovery of the secret is efficient due to the fast calculation of the hash function. The proposed scheme is flexible because of the use of existing hash functions.
A New Signature Scheme with Shared Verification
JIA Xiao-yun; LUO Shou-shan; YUAN Chao-wei
2006-01-01
With expanding user demands, digital signature techniques are also being expanded greatly, from single signature and single verification techniques to techniques supporting multi-users. This paper presents a new digital signature scheme vith shared verification based on the fiat-shamir signature scheme. This scheme is suitable not only for digital signatures of one public key, but also for situations where multiple public keys are required. In addition, the scheme can resist all kinds of collusion, making it more practicable and safer. Additionally it is more efficient than other schemes.
Colluding attacks on a group signature scheme
无
2005-01-01
Xie and Yu (2005) proposed a group signature scheme and claimed that it is the most efficient group signature scheme so far and secure. In this paper, we show that two dishonest group members can collude to launch two attacks on the scheme. In the first attack they can derive the group secret key and then generate untraceable group signatures. In the second attack, they can impersonate other group members once they see their signatures. Therefore we conclude that the signature scheme is not secure.We show that some parameters should be carefully selected in the scheme to resist our attacks.
Nonrepudiable Proxy Multi-Signature Scheme
LI JiGuo(李继国); CAO ZhenFu(曹珍富); ZHANG YiChen(张亦辰)
2003-01-01
The concept of proxy signature introduced by Mambo, Usuda, and Okamotoallows a designated person, called a proxy signer, to sign on behalf of an original signer. However,most existing proxy signature schemes do not support nonrepudiation. In this paper, two securenonrepudiable proxy multi-signature schemes are proposed that overcome disadvantages of theexisting schemes. The proposed schemes can withstand public key substitution attack. In addition,the new schemes have some other advantages such as proxy signature key generation and updatingusing insecure channels. This approach can also be applied to other ElGamal-like proxy signatureschemes.
ZHONG; Fengquan(仲峰泉); LIU; Nansheng(刘难生); LU; Xiyun(陆夕云); ZHUANG; Lixian(庄礼贤)
2002-01-01
In the present paper, a new dynamic subgrid-scale (SGS) model of turbulent stress and heat flux for stratified shear flow is proposed. Based on our calculated results of stratified channel flow, the dynamic subgrid-scale model developed in this paper is shown to be effective for large eddy simulation (LES) of stratified turbulent shear flows. The new SGS model is then applied to the LES of the stratified turbulent channel flow to investigate the coupled shear and buoyancy effects on the behavior of turbulent statistics, turbulent heat transfer and flow structures at different Richardson numbers.
Hybrid Transmission Scheme for MIMO Relay Channels
Guangming Xu
2009-11-01
Full Text Available To improve the achievable rate for the MIMO channels, we propose a hybrid transmission (HT scheme that mixes half-duplex decode-and-forward cooperative relaying transmission （DFRH）with direct transmission (DT. In the HT scheme, the source message is divided into two parts: one is transmitted by DFRH scheme and another is transmitted by DT scheme. Precoding and decoding are considered to convert the original MIMO relay channel into several parallel subchannels so that resource allocation can be easily performed. We focus on the spatial subchannel and power allocation problem. The objective of this problem is to maximize the total achievable rate under the constraints of joint total transmission power. Simulation results show that significant capacity gain can be achieved by the HT scheme compared to the DT scheme and the pure DFRH scheme.
High-Order Energy Stable WENO Schemes
Yamaleev, Nail K.; Carpenter, Mark H.
2008-01-01
A new third-order Energy Stable Weighted Essentially NonOscillatory (ESWENO) finite difference scheme for scalar and vector linear hyperbolic equations with piecewise continuous initial conditions is developed. The new scheme is proven to be stable in the energy norm for both continuous and discontinuous solutions. In contrast to the existing high-resolution shock-capturing schemes, no assumption that the reconstruction should be total variation bounded (TVB) is explicitly required to prove stability of the new scheme. A rigorous truncation error analysis is presented showing that the accuracy of the 3rd-order ESWENO scheme is drastically improved if the tuning parameters of the weight functions satisfy certain criteria. Numerical results show that the new ESWENO scheme is stable and significantly outperforms the conventional third-order WENO finite difference scheme of Jiang and Shu in terms of accuracy, while providing essentially nonoscillatory solutions near strong discontinuities.
Reiss, Martin; Chifflard, Peter
2016-04-01
Runoff generation processes in low mountain ranges in middle Europe are strongly influenced by lateral fluxes of soil water caused by periglacial cover beds. Less attention has been paid to the stratification of soils in hydrologic research as a major trigger of lateral slope water paths (REISS & CHIFFLARD 2014) although especially in the low mountain ranges in Middle Europe subsurface stormflow generation is strongly influenced by the periglacial cover beds (MOLDENHAUER et al. 2013) which are a typical example for stratified soils and almost widespread everywhere in the low mountain ranges. By contrast in soil science the Substrate-Oriented-Soil-Evolution-Model (LORZ et al. 2011) underlines the importance of stratified soils and lithological discontinuities (LD) as a key element controlling ecological processes and depth functions of soil properties. Whereas depth distributions of e.g. trace elements in the soil matrix at the point scale have been already detected, investigations of dissolved trace metal concentrations in the soil pore water and their depth distribution depending on soil stratification are scarce. Based on a typical depth distribution of trace metal concentrations in soil pore water depending on lithological discontinuities these depth functions may indicate zones of preferential transport. Additionally, there is still a missing link of investigations at different scales regarding the impacts of the geochemical barriers and the pronounced depth distributions on the chemical composition of the subsurface stormflow and consequently the hillslope runoff. Therefore, we validated the hypotheses that LDs act as geochemical barriers for their vertical distribution at the point and hillslope scale and that this typical depth functions of trace elements can be used to identify sources of subsurface stormflow at the catchment scale. To address these objectives, our research and sampling design is based on a multi-scale approach combining experimental
Diamessis, Peter J.; Gurka, Roi; Liberzon, Alex
2010-08-01
Proper orthogonal decomposition (POD) has been applied to two-dimensional transects of vorticity obtained from numerical simulations of the stratified turbulent wake of a towed sphere at a Reynolds number Re=(UD)/ν =5×103 and Froude number Fr=2U/(ND)=4 (U and D are characteristic velocity and length scales and N is the stratification frequency). At 231 times during the interval 12
Current practice with regard to short-term incentive schemes for middle managers
Chrisilla Grigoiadis
2007-01-01
Full Text Available This study aimed to determine what the current practice is with regard to short-term incentive schemes for middle managers. This was done by means of a quantitative study through a structured research survey completed by a sample of forty-eight organisations. The design elements, performance measures and payout practices of the various schemes in use were surveyed, as well as the participants’ view on the perceived effectiveness of their short-term incentive schemes. Evidence shows that the majority of organisations have a short-term incentive scheme in place for middle managers, and that the type of scheme used in most of the organisations is a performance-related bonus scheme, introduced mainly to drive business performance and reward superior performance.
Garaud, Pascale; Gagnier, Damien; Verhoeven, Jan
2017-03-01
Shear-induced turbulence could play a significant role in mixing momentum and chemical species in stellar radiation zones, as discussed by Zahn. In this paper we analyze the results of direct numerical simulations of stratified plane Couette flows, in the limit of rapid thermal diffusion, to measure the turbulent viscosity and the turbulent diffusivity of a passive tracer as a function of the local shear and the local stratification. We find that the stability criterion proposed by Zahn, namely that the product of the gradient Richardson number and the Prandtl number must be smaller than a critical values {(J\\Pr )}c for instability, adequately accounts for the transition to turbulence in the flow, with {(J\\Pr )}c≃ 0.007. This result recovers and confirms the prior findings of Prat et al. Zahn’s model for the turbulent diffusivity and viscosity, namely that the mixing coefficient should be proportional to the ratio of the thermal diffusivity to the gradient Richardson number, does not satisfactorily match our numerical data. It fails (as expected) in the limit of large stratification where the Richardson number exceeds the aforementioned threshold for instability, but it also fails in the limit of low stratification where the turbulent eddy scale becomes limited by the computational domain size. We propose a revised model for turbulent mixing by diffusive stratified shear instabilities that properly accounts for both limits, fits our data satisfactorily, and recovers Zahn’s model in the limit of large Reynolds numbers.
Scheme of thinking quantum systems
Yukalov, V I
2009-01-01
A general approach describing quantum decision procedures is developed. The approach can be applied to quantum information processing, quantum computing, creation of artificial quantum intelligence, as well as to analyzing decision processes of human decision makers. Our basic point is to consider an active quantum system possessing its own strategic state. Processing information by such a system is analogous to the cognitive processes associated to decision making by humans. The algebra of probability operators, associated with the possible options available to the decision maker, plays the role of the algebra of observables in quantum theory of measurements. A scheme is advanced for a practical realization of decision procedures by thinking quantum systems. Such thinking quantum systems can be realized by using spin lattices, systems of magnetic molecules, cold atoms trapped in optical lattices, ensembles of quantum dots, or multilevel atomic systems interacting with electromagnetic field.
Electrical injection schemes for nanolasers
Lupi, Alexandra; Chung, Il-Sug; Yvind, Kresten
2013-01-01
The performance of injection schemes among recently demonstrated electrically pumped photonic crystal nanolasers has been investigated numerically. The computation has been carried out at room temperature using a commercial semiconductor simulation software. For the simulations two electrical...... of 3 InGaAsP QWs on an InP substrate has been chosen for the modeling. In the simulations the main focus is on the electrical and optical properties of the nanolasers i.e. electrical resistance, threshold voltage, threshold current and wallplug efficiency. In the current flow evaluation the lowest...... threshold current has been achieved with the lateral electrical injection through the BH; while the lowest resistance has been obtained from the current post structure even though this model shows a higher current threshold because of the lack of carrier confinement. Final scope of the simulations...
Fragment separator momentum compression schemes
Bandura, Laura, E-mail: bandura@anl.gov [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); National Superconducting Cyclotron Lab, Michigan State University, 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Erdelyi, Bela [Argonne National Laboratory, Argonne, IL 60439 (United States); Northern Illinois University, DeKalb, IL 60115 (United States); Hausmann, Marc [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Kubo, Toshiyuki [RIKEN Nishina Center, RIKEN, Wako (Japan); Nolen, Jerry [Argonne National Laboratory, Argonne, IL 60439 (United States); Portillo, Mauricio [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Sherrill, Bradley M. [National Superconducting Cyclotron Lab, Michigan State University, 1 Cyclotron, East Lansing, MI 48824-1321 (United States)
2011-07-21
We present a scheme to use a fragment separator and profiled energy degraders to transfer longitudinal phase space into transverse phase space while maintaining achromatic beam transport. The first order beam optics theory of the method is presented and the consequent enlargement of the transverse phase space is discussed. An interesting consequence of the technique is that the first order mass resolving power of the system is determined by the first dispersive section up to the energy degrader, independent of whether or not momentum compression is used. The fragment separator at the Facility for Rare Isotope Beams is a specific application of this technique and is described along with simulations by the code COSY INFINITY.
Fragment separator momentum compression schemes.
Bandura, L.; Erdelyi, B.; Hausmann, M.; Kubo, T.; Nolen, J.; Portillo, M.; Sherrill, B.M. (Physics); (MSU); (Northern Illinois Univ.); (RIKEN)
2011-07-21
We present a scheme to use a fragment separator and profiled energy degraders to transfer longitudinal phase space into transverse phase space while maintaining achromatic beam transport. The first order beam optics theory of the method is presented and the consequent enlargement of the transverse phase space is discussed. An interesting consequence of the technique is that the first order mass resolving power of the system is determined by the first dispersive section up to the energy degrader, independent of whether or not momentum compression is used. The fragment separator at the Facility for Rare Isotope Beams is a specific application of this technique and is described along with simulations by the code COSY INFINITY.
Network Regulation and Support Schemes
Ropenus, Stephanie; Schröder, Sascha Thorsten; Jacobsen, Henrik
2009-01-01
-in tariffs to market-based quota systems, and network regulation approaches, comprising rate-of-return and incentive regulation. National regulation and the vertical structure of the electricity sector shape the incentives of market agents, notably of distributed generators and network operators....... This article seeks to investigate the interactions between the policy dimensions of support schemes and network regulation and how they affect the deployment of distributed generation. Firstly, a conceptual analysis examines how the incentives of the different market agents are affected. In particular......, it will be shown that there frequently exists a trade-off between the creation of incentives for distributed generators and for distribution system operators to facilitate the integration of distributed generation. Secondly, the interaction of these policy dimensions is analyzed, including case studies based...
Scheme of thinking quantum systems
Yukalov, V. I.; Sornette, D.
2009-11-01
A general approach describing quantum decision procedures is developed. The approach can be applied to quantum information processing, quantum computing, creation of artificial quantum intelligence, as well as to analyzing decision processes of human decision makers. Our basic point is to consider an active quantum system possessing its own strategic state. Processing information by such a system is analogous to the cognitive processes associated to decision making by humans. The algebra of probability operators, associated with the possible options available to the decision maker, plays the role of the algebra of observables in quantum theory of measurements. A scheme is advanced for a practical realization of decision procedures by thinking quantum systems. Such thinking quantum systems can be realized by using spin lattices, systems of magnetic molecules, cold atoms trapped in optical lattices, ensembles of quantum dots, or multilevel atomic systems interacting with electromagnetic field.
Network Regulation and Support Schemes
Ropenus, Stephanie; Schröder, Sascha Thorsten; Jacobsen, Henrik
2009-01-01
-in tariffs to market-based quota systems, and network regulation approaches, comprising rate-of-return and incentive regulation. National regulation and the vertical structure of the electricity sector shape the incentives of market agents, notably of distributed generators and network operators....... This article seeks to investigate the interactions between the policy dimensions of support schemes and network regulation and how they affect the deployment of distributed generation. Firstly, a conceptual analysis examines how the incentives of the different market agents are affected. In particular......, it will be shown that there frequently exists a trade-off between the creation of incentives for distributed generators and for distribution system operators to facilitate the integration of distributed generation. Secondly, the interaction of these policy dimensions is analyzed, including case studies based...
Improvement of Some Proxy Signature Schemes
LIJiguo; LIANGZhenghe; ZHUYuelong; HANGYichen
2005-01-01
In 1996, Mambo et al. introduced the concept of proxy signature. Proxy signature can be applied to mobile agent, e-vote etc. Recently, Sun and Hsieh showed that Lee et al's strong proxy signature scheme and its application to multi-proxy signature scheme, Shum and Wei's privacy-protected strong proxy signature scheme, and Park and Lee's nominative proxy signature scheme were all insecure against the original signer's forgery attack. In this paper, we show those proxy signature schemes don't withstand public key substitution attack and give some slight but important modifications for those proxy signature schemes such that the resulting schemes are secure against the original signer's forgery attack and public key substitution attack. In addition, we show that Park and Lee's nominative proxy signature scheme don't satisfy strong nonrepudiation and strong identifiability. Improved schemes satisfy all properties of strong proxy signature scheme, and doesn't use secure channel between the original signer and the proxy signer.
Numerical modeling of mixing in large stably stratified enclosures using TRACMIX++
Christensen, Jakob
This PhD dissertation focuses on the numerical modeling of stably stratified large enclosures. In stably stratified volumes, the distribution of temperature, species concentration etc become essentially 1-D throughout most of the enclosure. When the fluid in an enclosure is stratified, wall boundary buoyant jets, forced buoyant jets (injection of fluid) and natural convection plumes become the primary sources of mixing. The time constants for the buoyant jets may be considered as much smaller than the time constant for the mixing of the stratified ambient fluid, provided the combined volume occupied by the buoyant jets is small compared to the volume of the enclosure. Therefore, fluid transport by the buoyant jets may be considered as occurring instantaneously. For this reason this work focuses on deriving a numerical method which is able to solve the 1-D vertical fluid conservation equations, as given in Peterson (1994). Starting with the Eulerian fluid conservation equations given in Peterson (1994), a set of Lagrangian fluid conservation equations were derived. Combining the Lagrangian approach with operator splitting such that the convective step and the diffusive step is separated renders a very efficient, accurate, and stable numerical method as it is shown in this text. Since the stratified flow field frequently exhibits very strong gradients or so-called fronts, the generation of these fronts has to be accurately detected and tracked by the numerical method. Flow in stably stratified large enclosure has typically been modeled in the past using 1- or 2-zone models. The present model is new in that it belongs to the K-zone models where the number of zones is arbitrarily large and depends on the complexity of the solution and the accuracy requirement set by the user. Because fronts are present in the flow field, a Lagrangian type numerical method is used. A Lagrangian method facilitates front tracking and prevents numerical diffusion from altering the shape of
Flow and transport within a coastal aquifer adjacent to a stratified water body
Oz, Imri; Yechieli, Yoseph; Eyal, Shalev; Gavrieli, Ittai; Gvirtzman, Haim
2016-04-01
The existence of a freshwater-saltwater interface and the circulation flow of saltwater beneath the interface is a well-known phenomenon found at coastal aquifers. This flow is a natural phenomenon that occurs due to density differences between fresh groundwater and the saltwater body. The goals of this research are to use analytical, numerical, and physical models in order to examine the configuration of the freshwater-saltwater interface and the density-driven flow patterns within a coastal aquifer adjacent to long-term stratified saltwater bodies (e.g. meromictic lake). Such hydrological systems are unique, as they consist of three different water types: the regional fresh groundwater, and low and high salinity brines forming the upper and lower water layers of the stratified water body, respectively. This research also aims to examine the influence of such stratification on hydrogeological processes within the coastal aquifer. The coastal aquifer adjacent to the Dead Sea, under its possible future meromictic conditions, serves as an ideal example to examine these processes. The results show that adjacent to a stratified saltwater body three interfaces between three different water bodies are formed, and that a complex flow system, controlled by the density differences, is created, where three circulation cells are developed. These results are significantly different from the classic circulation cell that is found adjacent to non-stratified water bodies (lakes or oceans). In order to obtain a more generalized insight into the groundwater behavior adjacent to a stratified water body, we used the numerical model to perform sensitivity analysis. The hydrological system was found be sensitive to three dimensionless parameters: dimensionless density (i.e. the relative density of the three water bodies'); dimensionless thickness (i.e. the ratio between the relative thickness of the upper layer and the whole thickness of the lake); and dimensionless flux. The results
Gurka, R.; Diamessis, P.; Liberzon, A.
2009-04-01
The characterization of three-dimensional space and time-dependent coherent structures and internal waves in stratified environment is one of the most challenging tasks in geophysical fluid dynamics. Proper orthogonal decomposition (POD) is applied to 2-D slices of vorticity and horizontal divergence obtained from 3-D DNS of a stratified turbulent wake of a towed sphere at Re=5x103 and Fr=4. The numerical method employed solves the incompressible Navier-Stokes equations under the Boussinesq approximation. The temporal discretization consists of three fractional steps: an explicit advancement of the nonlinear terms, an implicit solution of the Poisson equation for the pseudo-pressure (which enforces incompressibility), and an implicit solution of the Helmholtz equation for the viscous terms (where boundary conditions are imposed). The computational domain is assumed to be periodic in the horizontal direction and non-periodic in the vertical direction. The 2-D slices are sampled along the stream-depth (Oxz), span-depth (Oyz) and stream-span planes (Oxy) for 231 times during the interval, Nt ∈ [12,35] (N is the stratification frequency). During this interval, internal wave radiation from the wake is most pronounced and the vorticity field in the wake undergoes distinct structural transitions. POD was chosen amongst the available statistical tools due to its advantage in characterization of simulated and experimentally measured velocity gradient fields. The computational procedure, applied to any random vector field, finds the most coherent feature from the given ensemble of field realizations. The decomposed empirical eigenfunctions could be referred to as "coherent structures", since they are highly correlated in an average sense with the flow field. In our analysis, we follow the computationally efficient method of 'snapshots' to find the POD eigenfunctions of the ensemble of vorticity field realizations. The results contains of the separate POD modes, along with
Increasing cancer detection yield of breast MRI using a new CAD scheme of mammograms
Tan, Maxine; Aghaei, Faranak; Hollingsworth, Alan B.; Stough, Rebecca G.; Liu, Hong; Zheng, Bin
2016-03-01
Although breast MRI is the most sensitive imaging modality to detect early breast cancer, its cancer detection yield in breast cancer screening is quite low (women) to date. The purpose of this preliminary study is to test the potential of developing and applying a new computer-aided detection (CAD) scheme of digital mammograms to identify women at high risk of harboring mammography-occult breast cancers, which can be detected by breast MRI. For this purpose, we retrospectively assembled a dataset involving 30 women who had both mammography and breast MRI screening examinations. All mammograms were interpreted as negative, while 5 cancers were detected using breast MRI. We developed a CAD scheme of mammograms, which include a new quantitative mammographic image feature analysis based risk model, to stratify women into two groups with high and low risk of harboring mammography-occult cancer. Among 30 women, 9 were classified into the high risk group by CAD scheme, which included all 5 women who had cancer detected by breast MRI. All 21 low risk women remained negative on the breast MRI examinations. The cancer detection yield of breast MRI applying to this dataset substantially increased from 16.7% (5/30) to 55.6% (5/9), while eliminating 84% (21/25) unnecessary breast MRI screenings. The study demonstrated the potential of applying a new CAD scheme to significantly increase cancer detection yield of breast MRI, while simultaneously reducing the number of negative MRIs in breast cancer screening.
Rapid Parameterization Schemes for Aircraft Shape Optimization
Li, Wu
2012-01-01
A rapid shape parameterization tool called PROTEUS is developed for aircraft shape optimization. This tool can be applied directly to any aircraft geometry that has been defined in PLOT3D format, with the restriction that each aircraft component must be defined by only one data block. PROTEUS has eight types of parameterization schemes: planform, wing surface, twist, body surface, body scaling, body camber line, shifting/scaling, and linear morphing. These parametric schemes can be applied to two types of components: wing-type surfaces (e.g., wing, canard, horizontal tail, vertical tail, and pylon) and body-type surfaces (e.g., fuselage, pod, and nacelle). These schemes permit the easy setup of commonly used shape modification methods, and each customized parametric scheme can be applied to the same type of component for any configuration. This paper explains the mathematics for these parametric schemes and uses two supersonic configurations to demonstrate the application of these schemes.
On Optimal Designs of Some Censoring Schemes
Dr. Adnan Mohammad Awad
2016-03-01
Full Text Available The main objective of this paper is to explore suitability of some entropy-information measures for introducing a new optimality censoring criterion and to apply it to some censoring schemes from some underlying life-time models. In addition, the paper investigates four related issues namely; the effect of the parameter of parent distribution on optimal scheme, equivalence of schemes based on Shannon and Awad sup-entropy measures, the conjecture that the optimal scheme is one stage scheme, and a conjecture by Cramer and Bagh (2011 about Shannon minimum and maximum schemes when parent distribution is reflected power. Guidelines for designing an optimal censoring plane are reported together with theoretical and numerical results and illustrations.
A Signature Scheme with Non-Repudiation
XIN Xiangjun; GUO Xiaoli; XIAO Guozhen
2006-01-01
Based on the Schnorr signature scheme, a new signature scheme with non-repudiation is proposed. In this scheme, only the signer and the designated receiver can verify the signature signed by the signer, and if necessary, both the signer and the designated receiver can prove and show the validity of the signature signed by the signer. The proof of the validity of the signature is noninteractive and transferable. To verify and prove the validity of the signature, the signer and the nominated receiver needn't store extra information besides the signature. At the same time, neither the signer nor the designated receiver can deny a valid signature signed. Then, there is no repudiation in this new signature scheme. According to the security analysis of this scheme, it is found the proposed scheme is secure against existential forgery on adaptive chosen message attack.
Hassanzadeh, Pedram
Large coherent vortices are abundant in geophysical and astrophysical flows. They play significant roles in the Earth's oceans and atmosphere, the atmosphere of gas giants, such as Jupiter, and the protoplanetary disks around forming stars. These vortices are essentially three-dimensional (3D) and baroclinic, and their dynamics are strongly influenced by the rotation and density stratification of their environments. This work focuses on improving our understanding of the physics of 3D baroclinic vortices in rotating and continuously stratified flows using 3D spectral simulations of the Boussinesq equations, as well as simplified mathematical models. The first chapter discusses the big picture and summarizes the results of this work. In Chapter 2, we derive a relationship for the aspect ratio (i.e., vertical half-thickness over horizontal length scale) of steady and slowly-evolving baroclinic vortices in rotating stratified fluids. We show that the aspect ratio is a function of the Brunt-Vaisala frequencies within the vortex and outside the vortex, the Coriolis parameter, and the Rossby number of the vortex. This equation is basically the gradient-wind equation integrated over the vortex, and is significantly different from the previously proposed scaling laws that find the aspect ratio to be only a function of the properties of the background flow, and independent of the dynamics of the vortex. Our relation is valid for cyclones and anticyclones in either the cyclostrophic or geostrophic regimes; it works with vortices in Boussinesq fluids or ideal gases, and non-uniform background density gradient. The relation for the aspect ratio has many consequences for quasi-equilibrium vortices in rotating stratified flows. For example, cyclones must have interiors more stratified than the background flow (i.e., super-stratified), and weak anticyclones must have interiors less stratified than the background (i.e., sub-stratified). In addition, this equation is useful to