Journal articles: 'Second phase sampling'

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Delmelle, Eric M., and Pierre Goovaerts. "Second-phase sampling designs for non-stationary spatial variables." Geoderma 153, no. 1-2 (October 2009): 205–16. http://dx.doi.org/10.1016/j.geoderma.2009.08.007.

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Li, H. G., H. T. Schreuder, D. D. Van Hooser, and G. E. Brink. "Estimating Strata Means in Double Sampling with Corrections Based on Second-Phase Sampling." Biometrics 48, no. 1 (March 1992): 189. http://dx.doi.org/10.2307/2532749.

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Kamba, Adamu Isah, Amos Adedayo Adewara, and Audu Ahmed. "Modified product estimator under two–phase sampling." Global Journal of Pure and Applied Sciences 25, no. 2 (September 6, 2019): 201–8. http://dx.doi.org/10.4314/gjpas.v25i2.10.

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In this paper, modification of product estimator under two-phase sampling was suggested. The modified product estimator was obtained through transformation in two cases using sample mean of auxiliary variables. Case one was when the second sample was drawn from the first sample while case two was when the second sample was drawn from the population. The bias and mean square error (MSE) of the modified product estimator was obtained. The theoretical and numerical validity of the modified product estimator under the two cases were determined to show it superiority to some considered existing product estimators. Numerical results shows that the modified product estimator under the two cases were more efficient than the considered existing estimators.Keywords: Product estimator, Two-Phase Sampling, Bias, Mean Square Error

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Singh, Rajesh, and Prayas Sharma. "Efficient Estimators Using Auxiliary Variable under Second Order Approximation in Simple Random Sampling and Two-Phase Sampling." Advances in Statistics 2014 (September 3, 2014): 1–9. http://dx.doi.org/10.1155/2014/974604.

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This paper suggests some estimators for population mean of the study variable in simple random sampling and two-phase sampling using information on an auxiliary variable under second order approximation. Bahl and Tuteja (1991) and Singh et al. (2008) proposed some efficient estimators and studied the properties of the estimators to the first order of approximation. In this paper, we have tried to find out the second order biases and mean square errors of these estimators using information on auxiliary variable based on simple random sampling and two-phase sampling. Finally, an empirical study is carried out to judge the merits of the estimators over others under first and second order of approximation.

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Ji, Chao, James D. Englehardt, and Cynthia Juyne Beegle-Krause. "Design of Real—Time Sampling Strategies for Submerged Oil Based on Probabilistic Model Predictions." Journal of Marine Science and Engineering 8, no. 12 (December 3, 2020): 984. http://dx.doi.org/10.3390/jmse8120984.

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Locating and tracking submerged oil in the mid depths of the ocean is challenging during an oil spill response, due to the deep, wide-spread and long-lasting distributions of submerged oil. Due to the limited area that a ship or AUV can visit, efficient sampling methods are needed to reveal the real distributions of submerged oil. In this paper, several sampling plans are developed for collecting submerged oil samples using different sampling methods combined with forecasts by a submerged oil model, SOSim (Subsurface Oil Simulator). SOSim is a Bayesian probabilistic model that uses real time field oil concentration data as input to locate and forecast the movement of submerged oil. Sampling plans comprise two phases: the first phase for initial field data collection prior to SOSim assessments, and the second phase based on the SOSim assessments. Several environmental sampling techniques including the systematic random, modified station plans as well zig-zag patterns are evaluated for the first phase. The data using the first phase sampling plan are then input to SOSim to produce submerged oil distributions in time. The second phase sampling methods (systematic random combined with the kriging-based sampling method and naive zig-zag sampling method) are applied to design the sampling plans within the submerged oil area predicted by SOSim. The sampled data obtained using the second phase sampling methods are input to SOSim to update the model’s assessments. The performance of the sampling methods is evaluated by comparing SOSim predictions using the sampled data from the proposed sampling methods with simulated submerged oil distributions during the Deepwater Horizon spill by the OSCAR (oil spill contingency and response) oil spill model. The proposed sampling methods, coupled with the use of the SOSim model, are shown to provide an efficient approach to guide oil spill response efforts.

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Sang, Hailin, Kenneth K. Lopiano, Denise A. Abreu, Andrea C. Lamas, Pam Arroway, and Linda J. Young. "Adjusting for Misclassification: A Three-Phase Sampling Approach." Journal of Official Statistics 33, no. 1 (March 1, 2017): 207–22. http://dx.doi.org/10.1515/jos-2017-0011.

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Abstract The United States Department of Agriculture’s National Agricultural Statistics Service (NASS) conducts the June Agricultural Survey (JAS) annually. Substantial misclassification occurs during the prescreening process and from field-estimating farm status for nonresponse and inaccessible records, resulting in a biased estimate of the number of US farms from the JAS. Here, the Annual Land Utilization Survey (ALUS) is proposed as a follow-on survey to the JAS to adjust the estimates of the number of US farms and other important variables. A three-phase survey design-based estimator is developed for the JAS-ALUS with nonresponse adjustment for the second phase (ALUS). A design-unbiased estimator of the variance is provided in explicit form.

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Mandallaz, Daniel. "A three-phase sampling extension of the generalized regression estimator with partially exhaustive information." Canadian Journal of Forest Research 44, no. 4 (April 2014): 383–88. http://dx.doi.org/10.1139/cjfr-2013-0449.

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We consider three-phase sampling schemes in which one component of the auxiliary information is known in the very large sample of the so-called null phase and the second component is available only in the large sample of the first phase, whereas the second phase provides the terrestrial inventory data. We extend to three-phase sampling the generalized regression estimator that applies when the null phase is exhaustive, for global and local estimation, and derive its asymptotic design-based variance. The new three-phase regression estimator is particularly useful for reducing substantially the computing time required to treat exhaustively very large data sets generated by modern remote sensing technology such as LiDAR.

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Fischer, Christoph, and Joachim Saborowski. "Variance estimation for mean growth from successive double sampling for stratification." Canadian Journal of Forest Research 50, no. 12 (December 2020): 1405–11. http://dx.doi.org/10.1139/cjfr-2020-0058.

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Double sampling for stratification (2SS) is a sampling design that is widely used for forest inventories. We present the mathematical derivation of two appropriate variance estimators for mean growth from repeated 2SS with updated stratification on each measurement occasion. Both estimators account for substratification based on the transition of sampling units among the strata due to the updated allocation. For the first estimator, sizes of the substrata were estimated from the second-phase sample (sample plots), whereas the respective sizes in the second variance estimator relied on the larger first-phase sample. The estimators were empirically compared with a modified version of Cochran’s well-known 2SS variance estimator that ignores substratification. This was done by performing bootstrap resampling on data from two German forest districts. The major findings were as follows: (i) accounting for substratification, as implemented in both new estimators, has substantial impact in terms of significantly smaller variance estimates and bias compared with the estimator without substratification, and (ii) the second estimator with substrata sizes being estimated from the first-phase sample shows a smaller bias than the first estimator.

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Šmelková, Ľ. "Inventory of plant material in forest nurseries by combining an ocular estimate and sampling measurements." Journal of Forest Science 48, No. 4 (May 17, 2019): 156–65. http://dx.doi.org/10.17221/11869-jfs.

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Two procedures of the plant material inventories in forest nurseries, used until now, are evaluated: ocular estimate and sampling. A new two-phase sampling procedure has been proposed on the basis of a suitable combination of estimation and counting and/or measurement of seedlings and plants. The optimum size of the sampling unit (length of bed segment) has been defined. The necessary number of bed segments on which the ocular estimation should be performed in the first phase (n1), and subsequently a more exact assessment of the number of individuals and/or their other qualitative and quantitative traits should be done in the second phase (n2), to achieve the required precision of results of ± 2 to 10% with reliability of 95%. A theoretical justification of the proposal as well as a detailed procedure of the accomplishment is presented. The frames have been specified where the proposed method is economically twice as beneficial as the classic sampling method.

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Mandallaz, Daniel, Jochen Breschan, and Andreas Hill. "New regression estimators in forest inventories with two-phase sampling and partially exhaustive information: a design-based Monte Carlo approach with applications to small-area estimation." Canadian Journal of Forest Research 43, no. 11 (November 2013): 1023–31. http://dx.doi.org/10.1139/cjfr-2013-0181.

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We consider two-phase sampling schemes where one component of the auxiliary information is known in every point (“wall-to-wall”) and a second component is available only in the large sample of the first phase, whereas the second phase yields a subsample with the terrestrial inventory. This setup is of growing interest in forest inventory thanks to the recent advances in remote sensing, in particular, the availability of LiDAR data. We propose a new two-phase regression estimator for global and local estimation and derive its asymptotic design-based variance. The new estimator performs better than the classical regression estimator. Furthermore, it can be generalized to cluster sampling and two-stage tree sampling within plots. Simulations and a case study with LiDAR data illustrate the theory.

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Mandallaz, Daniel, and Adrian Lanz. "Forest inventory: further results for optimal sampling schemes based on the anticipated variance." Canadian Journal of Forest Research 31, no. 10 (October 1, 2001): 1845–53. http://dx.doi.org/10.1139/x01-099.

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This work presents optimal allocation rules for two-phase, two-stage sampling schemes in which the sampling density and the costs of the second phase can vary over domains. The optimality criterion is based on the anticipated variance. It also gives an improved version of discrete approximation for the resulting inclusion probabilities. An example illustrates the theory.

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Zeeshan, S. M., and G. K. Vishwakarma. "Improved strategy for computation of population mean under double stratified sampling framework." Journal of Applied Mathematics, Statistics and Informatics 17, no. 2 (December 1, 2021): 91–102. http://dx.doi.org/10.2478/jamsi-2021-0011.

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Abstract The article contains a new technique to estimate the mean of the variate of the interest of the finite population with the help of two auxiliary variates. The technique complies well with the stratified population in which each strata proportion is predicted by taking an initial sample called the first phase sample. When the first phase sample is taken, a second sample is taken from the first sample which is called the second phase sample which is used to estimate the mean of the variate of the interest. In our study, we have considered the population which has two correlated auxiliary variates that pass almost through the origin. In such a situation ratio estimation technique and product estimation technique that provides improved estimates of the mean of the variate of the interest. Our technique considers a ratio-product type exponential estimator of which we have established efficiency theoretically as well as empirically.

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Yang, Haitao, Zongwu Xie, Cao Li, Xiaoyu Zhao, and Minghe Jin. "Path optimization of excavating manipulator in lunar soil sampling." Industrial Robot: An International Journal 43, no. 1 (January 18, 2016): 65–76. http://dx.doi.org/10.1108/ir-06-2015-0119.

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Purpose – The purpose of this paper is to study the path optimization method of the manipulator in the lunar soil excavation and sampling process. The current research is a practical need for the excavation and sampling of the lunar soil in the lunar exploration project. Design/methodology/approach – This paper proposes the objective function and constraints for path optimization during the excavation process of the lunar soil, regarding excavation time and energy consumption as the two key fitness indexes by analyzing the whole excavation process of the lunar soil. Specifically, the optimization is divided into two consecutive phases, one for the excavation path and the other one for joint motions. In the first phase, the Bézier polynomial is adopted to get the optimal excavation angle and reduce energy consumption. In the second phase, a method based on convex optimization, variable conversion and dynamic process discretization, is used to reduce excavation time and energy consumption. Findings – Controlled experiments on the fine sand and the simulant lunar soil were conducted to verify the feasibility and effectiveness of the two phases of the optimization method, respectively. Originality/value – The optimization method of the excavation tasks in this paper is of great value in theoretical and practical engineering, and it can be applied in other robotic operational tasks as well.

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Mandallaz, Daniel, and Alexander Massey. "Comparison of estimators in one-phase two-stage Poisson sampling in forest inventories." Canadian Journal of Forest Research 42, no. 10 (October 2012): 1865–71. http://dx.doi.org/10.1139/x2012-110.

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In the context of Poisson sampling, numerous adjustments to classical estimators have been proposed that are intended to compensate for inflated variance due to random sample size. However, such adjustments have never been applied to extensive forest inventories. This work investigates the performances of four estimators for the timber volume in one-phase two-stage forest inventories, where trees in the first stage are selected, at the plot level, by concentric circles or angle-count methods and a subset thereof are selected by Poisson sampling for further measurements to get a better estimation. The original two-stage estimator is the sum of two components: the first is the mean of Horwitz–Thompson estimators using simple volume approximations, based on diameter and species alone, of all first-stage trees in each inventory plot, and the second is the mean of Horwitz–Thompson estimators based on the differences between the simple volume approximations and refined volume determinations based on further diameter and height measurements on the second-stage trees within each inventory plot. This two-stage estimator is particularly useful because it provides unbiased estimates even if the simple prediction model is not correct, which is particularly important for small area estimation. The other three estimators rely on adjustments of the second component of the original estimator that are adapted from estimators proposed in the literature by L.R. Grosenbaugh and C.-E. Särndal. It turns out that these adjustments introduce a negligible bias and that the original simple estimator performs just as well or even better than the new estimators with respect to the variance.

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Grastien, Alban, and Enrico Scala. "Sampling Strategies for Conformant Planning." Proceedings of the International Conference on Automated Planning and Scheduling 28 (June 15, 2018): 97–105. http://dx.doi.org/10.1609/icaps.v28i1.13894.

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We present a generalisation of CPCES, a conformant planner that uses two procedures: candidate plan generation and sampling of the initial belief state. The new CPCES better distinguishes these two procedures and therefore provides a clearer framework for the resolution of conformant planning problems. We study CPCES theoretically by analysing the sampling phase through the lens of tags, width and basis. The benefit of this new interpretation is twofold: firstly it allows us to bound the maximum number of iterations required by CPCES, and second it allows us to individuate sampling strategies that guarantee the discovery of subsets of minimal bases. An experimental analysis reported in the paper shows that the greedy sampling (the original version of CPCES) is the more effective strategy, coverage wise. However, when either the quality of the plans or the size of the resulting samples is important a more sophisticated sampling is more effective.

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Baek, Jein. "Design of the Optimal Phase for the Interpolant Filter in the Second-order Bandpass Sampling System." Journal of the Institute of Electronics and Information Engineers 53, no. 3 (March 25, 2016): 132–39. http://dx.doi.org/10.5573/ieie.2016.53.3.132.

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Abou Ali, Hala, Reda Mazloum, and Sara Osama Ahmed. "A second phase sampling design for monitoring the nitrogen dioxide in Greater Cairo and Delta, Egypt." International Journal of Global Environmental Issues 19, no. 4 (2020): 295. http://dx.doi.org/10.1504/ijgenvi.2020.10039021.

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Ahmed, Sara Osama, Reda Mazloum, and Hala Abou Ali. "A second phase sampling design for monitoring the nitrogen dioxide in Greater Cairo and Delta, Egypt." International Journal of Global Environmental Issues 19, no. 4 (2020): 295. http://dx.doi.org/10.1504/ijgenvi.2020.115902.

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MILLER-IHLI, N. J. "Slurry Sampling Electrothermal Atomic Absorption Spectrometry: Results From the Second Phase of an International Collaborative Study." Journal of Analytical Atomic Spectrometry 12, no. 2 (1997): 205–12. http://dx.doi.org/10.1039/a606058g.

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Agarwal, Gaajendra K., Sira M. Allende, and Carlos N. Bouza. "Double Sampling with Ranked Set Selection in the Second Phase with Nonresponse: Analytical Results and Monte Carlo Experiences." Journal of Probability and Statistics 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/214959.

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This paper is devoted to the study of the behavior of the use of double sampling for dealing with nonresponses, when ranked set sample is used. The characteristics of the sampling strategies are derived. The structure of the errors generated the need of studying of the optimality of the strategies by performing a set Monte Carlo experiments.

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Fatima, Syeda Aliya, Syeda Tasneem Fatima, and S. Khurram Khan Alwi. "Major Causes of Female Dropouts at Different Educational Levels in Karachi." Global Educational Studies Review VI, no. I (March 30, 2021): 293–305. http://dx.doi.org/10.31703/gesr.2021(vi-i).30.

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This research revolves around the causes of female dropouts in Karachi at different educational levels, including primary, secondary, high school and university levels. In this research exploratory sequential mixed method has been used. After the literature review, the phenomenological research method for the qualitative phase of research has been adopted. In this regard, the interviews have been taken by different educationalists in Karachi on the basis of their experience and age via the convenience sampling method. All the hypotheses have been tested and accepted at this stage. Under the umbrella of results of the first phase, the questionnaire has been designed for quantitative research, i.e. the second phase of the research. The sample size for the second phase is 200; the data has been collected via quota sampling. The frequency of every element included in the quantitative phase has been detected separately by using descriptive analysis through SPSS. Finally, conclusions have been made on the basis of data analysis.

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Szatmári, Gábor, Péter László, Katalin Takács, József Szabó, Zsófia Bakacsi, Sándor Koós, and László Pásztor. "Optimization of second-phase sampling for multivariate soil mapping purposes: Case study from a wine region, Hungary." Geoderma 352 (October 2019): 373–84. http://dx.doi.org/10.1016/j.geoderma.2018.02.030.

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Mandallaz, D. "Optimal sampling schemes based on the anticipated variance with lack of fit." Canadian Journal of Forest Research 32, no. 12 (December 1, 2002): 2236–43. http://dx.doi.org/10.1139/x02-145.

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This note presents an important improvement for optimal sampling schemes based on the anticipated variance. The anticipated variance is defined as the average of the design-based variance under a simple stochastic model in which the trees are assumed to be uniformly and independently distributed within a given number of so-called Poisson strata. We consider two-phase two-stage cluster sampling schemes in which costs and terrestrial second-phase sampling density can vary over domains. The estimation procedure is based on post-stratification with respect to so-called working strata that do not need to be identical with the Poisson strata, usually unknown, which induces a lack of fit. It is then possible to derive analytically the optimal sampling schemes. Data from the Swiss National Inventory illustrates the method.

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Liu, Yiyang, Yang Zhao, Shuaihua Yan, Chunhe Song, and Fei Li. "A Sampling-Based Algorithm with the Metropolis Acceptance Criterion for Robot Motion Planning." Sensors 22, no. 23 (November 26, 2022): 9203. http://dx.doi.org/10.3390/s22239203.

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Motion planning is one of the important research topics of robotics. As an improvement of Rapidly exploring Random Tree (RRT), the RRT* motion planning algorithm is widely used because of its asymptotic optimality. However, the running time of RRT* increases rapidly with the number of potential path vertices, resulting in slow convergence or even an inability to converge, which seriously reduces the performance and practical value of RRT*. To solve this issue, this paper proposes a two-phase motion planning algorithm named Metropolis RRT* (M-RRT*) based on the Metropolis acceptance criterion. First, to efficiently obtain the initial path and start the optimal path search phase earlier, an asymptotic vertex acceptance criterion is defined in the initial path estimation phase of M-RRT*. Second, to improve the convergence rate of the algorithm, a nonlinear dynamic vertex acceptance criterion is defined in the optimal path search phase, which preferentially accepts vertices that may improve the current path. The effectiveness of M-RRT* is verified by comparing it with existing algorithms through the simulation results in three test environments.

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Anieting, Akan. "Two- Phase Stratified Sampling Estimator for Population Mean in The Presence of Nonresponse Using Single Auxiliary Variable." Mathematical Journal of Interdisciplinary Sciences 8, no. 2 (March 30, 2020): 49–56. http://dx.doi.org/10.15415/mjis.2020.82006.

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In this article, a new estimator for population mean in two-phase stratified sampling in the presence of nonresponse using single auxiliary variable has been proposed. The bias and Mean Squared Error (MSE) of the proposed estimator has been given using large sample approximation. The empirical study shows that the MSE of the proposed estimator is more efficient than existing estimators. The optimum values of first and second phase sample have been determined.

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Barral, Julien, and Stéphane Seuret. "RANDOM SPARSE SAMPLING IN A GIBBS WEIGHTED TREE AND PHASE TRANSITIONS." Journal of the Institute of Mathematics of Jussieu 19, no. 1 (May 9, 2018): 65–116. http://dx.doi.org/10.1017/s1474748017000433.

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Let $\unicode[STIX]{x1D707}$ be the projection on $[0,1]$ of a Gibbs measure on $\unicode[STIX]{x1D6F4}=\{0,1\}^{\mathbb{N}}$ (or more generally a Gibbs capacity) associated with a Hölder potential. The thermodynamic and multifractal properties of $\unicode[STIX]{x1D707}$ are well known to be linked via the multifractal formalism. We study the impact of a random sampling procedure on this structure. More precisely, let $\{{I_{w}\}}_{w\in \unicode[STIX]{x1D6F4}^{\ast }}$ stand for the collection of dyadic subintervals of $[0,1]$ naturally indexed by the finite dyadic words. Fix $\unicode[STIX]{x1D702}\in (0,1)$, and a sequence $(p_{w})_{w\in \unicode[STIX]{x1D6F4}^{\ast }}$ of independent Bernoulli variables of parameters $2^{-|w|(1-\unicode[STIX]{x1D702})}$. We consider the (very sparse) remaining values $\widetilde{\unicode[STIX]{x1D707}}=\{\unicode[STIX]{x1D707}(I_{w}):w\in \unicode[STIX]{x1D6F4}^{\ast },p_{w}=1\}$. We study the geometric and statistical information associated with $\widetilde{\unicode[STIX]{x1D707}}$, and the relation between $\widetilde{\unicode[STIX]{x1D707}}$ and $\unicode[STIX]{x1D707}$. To do so, we construct a random capacity $\mathsf{M}_{\unicode[STIX]{x1D707}}$ from $\widetilde{\unicode[STIX]{x1D707}}$. This new object fulfills the multifractal formalism, and its free energy is closely related to that of $\unicode[STIX]{x1D707}$. Moreover, the free energy of $\mathsf{M}_{\unicode[STIX]{x1D707}}$ generically exhibits one first order and one second order phase transition, while that of $\unicode[STIX]{x1D707}$ is analytic. The geometry of $\mathsf{M}_{\unicode[STIX]{x1D707}}$ is deeply related to the combination of approximation by dyadic numbers with geometric properties of Gibbs measures. The possibility to reconstruct $\unicode[STIX]{x1D707}$ from $\widetilde{\unicode[STIX]{x1D707}}$ by using the almost multiplicativity of $\unicode[STIX]{x1D707}$ and concatenation of words is discussed as well.

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Huang, Ying. "Evaluating and comparing biomarkers with respect to the area under the receiver operating characteristics curve in two-phase case–control studies." Biostatistics 17, no. 3 (February 16, 2016): 499–522. http://dx.doi.org/10.1093/biostatistics/kxw003.

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Abstract Two-phase sampling design, where biomarkers are subsampled from a phase-one cohort sample representative of the target population, has become the gold standard in biomarker evaluation. Many two-phase case–control studies involve biased sampling of cases and/or controls in the second phase. For example, controls are often frequency-matched to cases with respect to other covariates. Ignoring biased sampling of cases and/or controls can lead to biased inference regarding biomarkers' classification accuracy. Considering the problems of estimating and comparing the area under the receiver operating characteristics curve (AUC) for a binary disease outcome, the impact of biased sampling of cases and/or controls on inference and the strategy to efficiently account for the sampling scheme have not been well studied. In this project, we investigate the inverse-probability-weighted method to adjust for biased sampling in estimating and comparing AUC. Asymptotic properties of the estimator and its inference procedure are developed for both Bernoulli sampling and finite-population stratified sampling. In simulation studies, the weighted estimators provide valid inference for estimation and hypothesis testing, while the standard empirical estimators can generate invalid inference. We demonstrate the use of the analytical variance formula for optimizing sampling schemes in biomarker study design and the application of the proposed AUC estimators to examples in HIV vaccine research and prostate cancer research.

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Tiwari, Ashish, Manish Kumar, and Sarvesh Kumar Dubey. "A Generalized Approach for Estimation of a Finite Population Mean in Two-Phase Sampling." Asian Journal of Probability and Statistics 21, no. 3 (March 13, 2023): 45–58. http://dx.doi.org/10.9734/ajpas/2023/v21i3467.

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The present paper deals with the formulation of a generalized class of ratio-cum-product estimators for the estimation of a finite population mean in two-phase sampling. The mathematical expressions for the mean square errors (MSEs) of the preliminary and proposed estimators are derived. It has been established that the proposed class encompasses a wide range of estimators for specific choices of the scalars. The relative performance of the proposed class, as compared to the preliminary estimators, is evaluated using the MSE criterion. In addition, optimum sample sizes of the first-phase and second-phase samples are obtained using a specified cost function. The theoretical findings are empirically assessed by computing MSEs and percent relative efficiencies (PREs) of various estimators based on real population datasets. The findings of the study reveal that the proposed class of estimators are superior as compared to the preliminary estimators for the estimation of mean.

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Dudney, C. S., D. L. Wilson, R. B. Gammage, and H. L. Scott. "The Department of Energy's Radon Testing Programme." Radiation Protection Dosimetry 56, no. 1-4 (December 1, 1994): 247–50. http://dx.doi.org/10.1093/oxfordjournals.rpd.a082463.

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Abstract The US Department of Energy (DOE) conducted an initial study of indoor radon in buildings under its control in response to Public Law 100-551, the Indoor Radon Abatement Act, enacted by the US Congress in 1988. Other federal agencies have also conducted radon surveys. This paper presents an overview of the results from radon testing of several thousand buildings ranging from 100 m2 to over 10,000 m2 in size. In addition, results from groups of buildings have been examined, classified according to ventilation and usage characteristics. So far, there is no apparent difference among building classes. The paper also discusses a proposal for phased radon surveys. It is suggested that first-phase results can be used to identify facilities with radon problems. In the second phase, measurements can be made at a much higher sampling density at facilities with radon problems. The results of the second phase are expected to identify all buildings in need of mitigation.

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Meadseena, Arun, and Jiraporn Chano. "Enhancing English Language Skills of Upper Secondary Students through Content and Language Integrated Learning." Journal of Educational Issues 9, no. 1 (January 30, 2023): 72. http://dx.doi.org/10.5296/jei.v9i1.20597.

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The purposes of this research aimed to enhance English language skills of upper secondary students through content and language integrated learning. The research procedures involved three phases as following: the first phase studied fundamental information. The second phase designed and developed the instructional strategies. The third phase implemented instructional model to enhance English language skills through content and language integrated learning. Forty of 11th grade students, second semester of academic year of 2018 selected through cluster random sampling. The assessment tools were a questionnaire, an achievement test, an English language skills test, and a satisfaction questionnaire. The result showed that students improved their listening and speaking skills. Achievement learning from the students is a result that has been achieved by students who obtain listening and speaking skills. At the 0.5 level of statistical significance, Students who were taught using content and language integrated learning outperformed those who were taught using traditional methods. CLIL learning provided students with a high level of learning satisfaction.

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Cho, Chihyun, Hyunji Koo, Jae-Yong Kwon, and Joo-Gwang Lee. "Phase calibration and uncertainty evaluation for a RF comb generator." Measurement and Control 53, no. 3-4 (January 29, 2020): 698–703. http://dx.doi.org/10.1177/0020294019901301.

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In this paper, we present calibration and uncertainty evaluation methods for the phase of a radio-frequency comb generator using a calibrated sampling oscilloscope. In addition, we present many solutions that are indispensable for the precise calibration of phase up to 50 GHz. First, we correct the sampling time error, which is the systematic error of the equivalent time sampling system. Second, the frequency response of the oscilloscope is de-convoluted from the measured pulse, and the impedance mismatch between the radio-frequency comb generator and the oscilloscope is calibrated. Finally, we present the calibrated phase of the radio-frequency comb generator and the measurement uncertainty, which demonstrated 95% confidence intervals within ±4.4° up to 50 GHz. The calibrated radio-frequency comb generator, which is traceable to SI units, is used to calibrate a nonlinear vector network analyzer, vector signal analyzer, and oscilloscope. Uncertainties are easily propagated to the measurement uncertainty of other apparatus since it is obtained in the form of covariance.

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Takeuchi, Makoto, and Haruo Saito. "Absolute measurement of sampling jitter in audio equipment." Journal of the Acoustical Society of America 154, no. 1 (July 1, 2023): 443–53. http://dx.doi.org/10.1121/10.0020291.

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This study proposes a method for analyzing sampling jitter in audio equipment based on the time-domain analysis, considering the temporal fluctuations of the zero-crossing points in the recorded sinusoidal waves to characterize the jitter. This method enabled the separate evaluation of jitter in an audio player from those in audio recorders when the same playback signal is simultaneously fed into two audio recorders. The experiments were conducted using commercially available portable devices with a maximum sampling rate of 192 000 samples per second. The results demonstrated that jitter values on the order of a few tens of picoseconds can be identified in an audio player. Moreover, the proposed method enabled the separation of jitter from phase-independent noise utilizing the left and right channels of the audio equipment. As such, this method is applicable for performance evaluation of audio equipment, signal generators, and clock sources.

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Nunemaker, Craig S., David H. Wasserman, Owen P. McGuinness, Ian R. Sweet, Jeanette C. Teague, and Leslie S. Satin. "Insulin secretion in the conscious mouse is biphasic and pulsatile." American Journal of Physiology-Endocrinology and Metabolism 290, no. 3 (March 2006): E523—E529. http://dx.doi.org/10.1152/ajpendo.00392.2005.

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Islets in most species respond to increased glucose with biphasic insulin secretion, marked by a sharp first-phase peak and a slowly rising second phase. Mouse islets in vitro, however, lack a robust second phase. To date, this observation has not been extended in vivo. We thus compared insulin secretion from conscious mice with isolated mouse islets in vitro. The arterial plasma insulin response to a hyperglycemic clamp was measured in conscious mice 1 wk after surgical implantation of carotid artery and jugular vein catheters. Mice were transfused using clamps with blood from a donor mouse to maintain blood volume, allowing frequent arterial sampling. When plasma glucose in vivo was raised from ∼5 to ∼13 mM, insulin rose to a first-phase peak of 403 ± 73% above basal secretion ( n = 5), followed by a rising second phase of mean 289 ± 41%. In contrast, perifused mouse islets (∼75 islets/trial) responded with a similar first phase of 508 ± 94% ( n = 4) but a smaller and virtually flat second phase of 169 ± 9% ( n = 4, P < 0.05). Furthermore, the slope of the second-phase response differed significantly from zero in mice (2.63 ± 0.39%/min, P < 0.01), in contrast to perifused islets (0.18 ± 0.14%/min, P > 0.30). Mice also displayed pulsatile patterns in insulin concentration (period: 4.2 ± 0.4 min, n = 8). Conscious mice thus responded to increased glucose with biphasic and pulsatile insulin secretion, as in other species. The robust second phase observed in vivo suggests that the processes needed to generate second-phase insulin secretion may be abrogated by islet isolation.

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Cahyadi, Ani, Hendryadi Hendryadi, and Suryani Suryani. "Thoughts on Incivility: A Preliminary Study to Identify Uncivil Behavior in Indonesian Higher Education." Journal of Ethnic and Cultural Studies 8, no. 1 (December 1, 2020): 129. http://dx.doi.org/10.29333/ejecs/593.

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This preliminary study aims to identify an item list of uncivil behaviors in the Indonesian educational environment. The study comprises three phases: first, a panel of experts assessed each item to ensure their content validity for items pool. The second phase used a cross-sectional design and convenience sampling to recruit 524 students and faculty members in seven provinces in Indonesia using an online survey. The third phase involved ten students from the second phase and several faculty representatives were randomly selected to complete the open-ended questionnaire. Principal component analysis (PCA) identified four factors, including disregard for instructors/annoyances, disrespect for others (verbal and non-verbal), misconduct and integrity violation, and use of cell phones. Furthermore, the results indicate that "getting up during a class,leaving and returning,” “arriving late and/or leaving early," “not paying attention in the class,” “texting,” “packing books before the class is dismissed,” “cheating during an exam,” and “sleeping during the class” were the top seven highest recurring behaviors. This study provides tentative support for a preliminary scale in identifying uncivil behavior among college populations in Indonesia.

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Batool, Faiza, Dr Najma Sadiqa, and Dr Ume Laila. "Second Screen Phenomena and News Consumption in Pakistan." Journal of Peace, Development & Communication Volume 4, Issue 3 (December 31, 2020): 63–88. http://dx.doi.org/10.36968/jpdc-v04-i03-05.

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The second screen phenomenon is a hybrid media process referring to the complementary and simultaneous use of television and a second web-connected screen for media consumption. The present study examined the impact of demographic characteristics (i.e. gender, age, education, and income) on audience activity for second screen news consumption in Pakistan. An online survey based on snowball sampling was conducted from 400 respondents. The results showed that gender only plays a role in usage during post exposure. The age was comparatively a strong predictor of audience activity. It has a positive relationship with involvement during exposure and usage during post exposure phase of second screen news consumption. Our study contributes to the existing literature by identifying the predictors for changing news consumption patterns in the new media eco-system and helps in a better understanding of contemporary media audiences.

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Ngo, Linh Dan, Dumitru Duca, Yvain Carpentier, Jennifer A. Noble, Raouf Ikhenazene, Marin Vojkovic, Cornelia Irimiea, et al. "Chemical discrimination of the particulate and gas phases of miniCAST exhausts using a two-filter collection method." Atmospheric Measurement Techniques 13, no. 2 (February 28, 2020): 951–67. http://dx.doi.org/10.5194/amt-13-951-2020.

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Abstract. Combustion of hydrocarbons produces both particulate- and gas-phase emissions responsible for major impacts on atmospheric chemistry and human health. Ascertaining the impact of these emissions, especially on human health, is not straightforward because of our relatively poor knowledge of how chemical compounds are partitioned between the particle and gas phases. Accordingly, we propose coupling a two-filter sampling method with a multi-technique analytical approach to fully characterize the particulate- and gas-phase compositions of combustion by-products. The two-filter sampling method is designed to retain particulate matter (elemental carbon possibly covered in a surface layer of adsorbed molecules) on a first quartz fiber filter while letting the gas phase pass through and then trap the most volatile components on a second black-carbon-covered filter. All samples thus collected are subsequently subjected to a multi-technique analytical protocol involving two-step laser mass spectrometry (L2MS), secondary ion mass spectrometry (SIMS), and micro-Raman spectroscopy. Using the combination of this two-filter sampling–multi-technique approach in conjunction with advanced statistical methods, we are able to unravel distinct surface chemical compositions of aerosols generated with different set points of a miniCAST burner. Specifically, we successfully discriminate samples by their volatile, semi-volatile, and non-volatile polycyclic aromatic hydrocarbon (PAH) contents and reveal how subtle changes in combustion parameters affect particle surface chemistry.

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Zacks, Shelemyahu. "Two-stage and sequential sampling for estimation and testing with prescribed precision." Encyclopedia with Semantic Computing and Robotic Intelligence 01, no. 01 (March 2017): 1650004. http://dx.doi.org/10.1142/s2425038416500048.

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Statistical data analysis includes several phases. First, there is the phase of data collection. Second, there is the phase of analysis and inference. The two phases are interconnected. There are two types of data analysis. One type is called parametric and the other type is nonparametric. In the present paper, we discuss parametric inference. In parametric inference, we model the results of a given experiment as realization of random variables having a particular distribution, which is specified by its parameters. A random sample is a sequence of independent and identically distributed (i.i.d.) random variables. Statistics are functions of the data in the sample, which do not involve unknown parameters. A statistical inference is based on statistics of a given sample. We discuss two kinds of parametric inference. Estimating the values of parameters, or testing hypotheses concerning the parameters in either kind of inference, we are concerned with the accuracy and precision of the results. In estimation of parameters, the results are precise if, with high probability, they belong to a specified neighborhoods of the parameters. In testing hypotheses, one has to decide which one of two or several hypotheses should be accepted. Hypotheses which are not accepted are rejected. We distinguish between two types of errors. Type I error is the one committed by rejecting a correct hypothesis. Type II is that of accepting a wrong hypothesis. It is desired that both types of errors will occur simultaneously with small probabilities. Both precision in estimation or small error probabilities in testing depend on the statistics used (estimators or test functions) and on the sample size. In this paper, we present sampling procedures that attain the desired objectives. In Sec. 2, we discuss estimation of the parameters of a binomial distribution. In Sec. 3, more general results about estimation of expected values are presented. In Sec. 4, we discuss the Wald Sequential Probability Ratio Test (SPRT), which has optimal properties for testing two simple hypotheses.

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Agusti, Fardatil Aini, Afifah Zafirah, Engkizar Engkizar, Fuady Anwar, Zainul Arifin, and Syafrimen Syafril. "THE IMPLANTATION OF CHARACTER VALUES TOWARD STUDENTS THROUGH CONGKAK GAME FOR MATHEMATICS INSTRUCTIONAL MEDIA." Jurnal Penelitian Pendidikan 35, no. 2 (December 17, 2018): 132–42. http://dx.doi.org/10.15294/jpp.v35i2.13947.

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This research aims to investigate character values that can be applied on students through congkak game as it is used as a media of mathematics learning. This study used qualitative and quantitative combination or (Exploratory mixed methods designs). The first phase of qualitative data was taken through in-depth interviews to 5 selected informants using purposive sampling technique. The first phase of the data retrieval was intended to gather information related to the content of character values contained in congkak game. All data interviews were analyzed thematically using NVivo qualitative analysis tool 10. Then, the second phase of the data was taken using a questionnaire to 46 students who were studying in grade V and VI in an elementary school (SD). The second phase of the data retrieval was intended to support the first phase of the research results, the entire data of the second phase analyzed descriptively using quantitative analysis tools SPSS Windows 18.0. Overall, the results of the two phases indicated that there were nine character values contained in the game congkak once it was used as a medium of mathematics learning. The nine-character values were honesty, discipline, hard working, creativity, curiosity, independent, communicativeness, responsibility and appreciation for achievements. The results also proved that the use of instructional media such as traditional game congkak can be used as an intermediary that can be used by teachers in mathematics learning process. In addition, this study shows that even though congkak game belongs to a traditional game among middle societies, in fact, there were characters values as it was investigated scientifically.

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Hernández-Sánchez, Mónica, Francisco-Shu Kitaura, Metin Ata, and Claudio Dalla Vecchia. "Higher order Hamiltonian Monte Carlo sampling for cosmological large-scale structure analysis." Monthly Notices of the Royal Astronomical Society 502, no. 3 (January 21, 2021): 3976–92. http://dx.doi.org/10.1093/mnras/stab123.

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ABSTRACT We investigate higher order symplectic integration strategies within Bayesian cosmic density field reconstruction methods. In particular, we study the fourth-order discretization of Hamiltonian equations of motion (EoM). This is achieved by recursively applying the basic second-order leap-frog scheme (considering the single evaluation of the EoM) in a combination of even numbers of forward time integration steps with a single intermediate backward step. This largely reduces the number of evaluations and random gradient computations, as required in the usual second-order case for high-dimensional cases. We restrict this study to the lognormal-Poisson model, applied to a full volume halo catalogue in real space on a cubical mesh of 1250 h−1 Mpc side and 2563 cells. Hence, we neglect selection effects, redshift space distortions, and displacements. We note that those observational and cosmic evolution effects can be accounted for in subsequent Gibbs-sampling steps within the COSMIC BIRTH algorithm. We find that going from the usual second to fourth order in the leap-frog scheme shortens the burn-in phase by a factor of at least ∼30. This implies that 75–90 independent samples are obtained while the fastest second-order method converges. After convergence, the correlation lengths indicate an improvement factor of about 3.0 fewer gradient computations for meshes of 2563 cells. In the considered cosmological scenario, the traditional leap-frog scheme turns out to outperform higher order integration schemes only when considering lower dimensional problems, e.g. meshes with 643 cells. This gain in computational efficiency can help to go towards a full Bayesian analysis of the cosmological large-scale structure for upcoming galaxy surveys.

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Bogard, D. G., and W. G. Tiederman. "Characteristics of ejections in turbulent channel flow." Journal of Fluid Mechanics 179 (June 1987): 1–19. http://dx.doi.org/10.1017/s002211208700140x.

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Quantitative measurements of the structure of ejections from the wall region have been made using conditional-sampling techniques. Discrete ejections from a burst event were identified using fluorescent-dye flow visualization simultaneously with streamwise, u, and normal, v, velocity measurements. These velocity measurements, at y+ = 15, were conditionally sampled based on different phases of the ejection event. Features of the ejection which were educed from the conditional sampling were found to be very sensitive to the phase alignment. Results showed that ejections were characterized by a rapid deceleration at the leading edge followed by a strong positive velocity gradient at the trailing edge. An intense second-quadrant uv spike occurred immediately following the leading edge. This uv peak was highly correlated with a positive peak in the v velocity. The first ejection which occurred in a burst was found to be significantly more intense than the following ejections. Many characteristics of bursts which have been obtained from previous conditional-sampling studies were found to correspond to different phases of the ejection event.

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Ahmed, Ishfaq, and Muhammad Musarrat Nawaz. "An exploration of students’ knowledge and understanding of Istihalah." Journal of Islamic Marketing 7, no. 2 (June 13, 2016): 213–31. http://dx.doi.org/10.1108/jima-09-2014-0059.

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Purpose The purpose of this study is to investigate the level of understanding of Muslim students about Istihalah. It compares the understanding of students of various departments about Istihalah and changes in their knowledge after a workshop. Design/methodology/approach The study is conducted in two phases. In the first phase, a comparison is made between students of three departments: Islamic studies, business studies and food sciences. These departments were selected using purposive sampling. In the second phase, students with a lack of awareness about Istihalah were given a one-day training workshop on the concept of Istihalah. Data were collected through a personally administrated questionnaire. Findings The results of the first phase revealed that students from business studies and food sciences were not familiar with the concept and application of Istihalah, whereas students from Islamic studies were well-aware of it. The findings of the second phase revealed that after the provision of training (workshop), students were at par with the students of Islamic studies. All the students were further willing to know about Istihalah and its implications in their personal and professional lives. Originality/value The main contribution of this study is to highlight the area where information about Islamic concepts should be disseminated and applied.

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Stellingwerf, D. A., and A. de Gier. "Monitoring changes in timber volume using aerial photo plots and field plots in a two-phase sampling design." Netherlands Journal of Agricultural Science 36, no. 2 (May 1, 1988): 119–25. http://dx.doi.org/10.18174/njas.v36i2.16685.

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Standing timber volume and mean periodic volume increment (of Norway spruce - Picea abies - age 40-100 yr) were determined over a period of 10 yr (1974-84) in a 3000 ha forest area in Austria. The results of a Two-Phase Linear Regression Sampling (TPLRS) method (using 112 circular photo plots in the first phase, and 55 dependent field plots in the second phase, each covering 0.05 ha) were compared with those of a Simple Random Sample (SRS) of only field plots (112). The crown cover percentages per plot were taken as independent variables in the TPLRS. They were stereoscopically determined on 1:10 000 scale black and white infrared aerial photographs of 1974 and 1984. Results from TPLRS were comparable to those from SRS and did not require re-enumeration of the field plots in 1984. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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Yao, Guo Zhong, Li Si Ai, Li Zhong Shen, and Gui Yong Wang. "Research on the High-Speed Data Acquisition System Based on Clock Distribution." Advanced Materials Research 834-836 (October 2013): 1039–46. http://dx.doi.org/10.4028/www.scientific.net/amr.834-836.1039.

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In order to digitize the signal of high frequency or ultra-high frequency, clock distribution technology with the same frequency but different phase is utilized as a solution to this difficulty. The principles of high-speed analog-to-digit converter (ADC) by the lower rate ADC module, key technology and key module of the data acquisition systems are studied. From the aspects of system architecture, clock distribution module based on the AD9520, ADC module based on the AD9480 and data processing, the design method of ultra-high-speed ADC by clock distribution mode are explored. The results show that: driving many ADC modules with serial clocks of the same frequency but different phase in parallel to sample the same signal, the sampling frequency of the ADC system is the sum of each ADC sampling frequency. Four AD9480 modules are driven by four-way 250MHz clocks with phase fault 90°, respectively. And 1GHz samples per second can be attained, which is four times of the sampling frequency by monolithic AD9480.

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Jantakun, Thiti, Kitsadaporn Jantakun, and Thada Jantakoon. "STEAM Education Using Design Thinking Process Through Virtual Communities of Practice (STEAM-DT-VCoPs)." Journal of Educational Issues 7, no. 1 (April 23, 2021): 249. http://dx.doi.org/10.5296/jei.v7i1.18420.

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These objectives of the study are 1) to design STEAM education using Design Thinking Process through Virtual Communities of Practice (STEAM-DT-VCoPs), and 2) to evaluate the designed STEAM-DT-VCoPs. It divides the research procedures into two phases. The first phase is to design STEAM-DT-VCoPs, and the second phase is to evaluate the STEAM-DT-VCoPs. The sample group of this study comprises fourteen experts selected by purposive sampling. The arithmetic mean and standard deviation analyzed data. The research findings are: 1) The STEAM-DT-VCoPs comprise three steps are 1.1) the role of virtual communities of STEAM practice 1.2) Design Thinking Process through Virtual Communities of Practice, and 1.3) the various disciplines in STEAM education. 2) The experts agree that STEAM-DT-VCoPs is the highest level of appropriateness.

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Perreault, Andrea M. J., Nan Zheng, and Noel G. Cadigan. "Estimation of growth parameters based on length-stratified age samples." Canadian Journal of Fisheries and Aquatic Sciences 77, no. 3 (March 2020): 439–50. http://dx.doi.org/10.1139/cjfas-2019-0129.

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Response-selective stratified sampling (RSSS) has been well studied in the statistical literature; however, the application of the resulting statistical theories and methods to a specific case of RSSS in fisheries studies, namely length-stratified age sampling (LSAS), is inadequate. We review nine estimation approaches for RSSS found in the statistical and fisheries science literature in terms of three sampling components: the first phase length composition sample, the second phase age composition sample, and the sampling scheme. We compare the performance in terms of RRMSE (relative root mean squared error) for von Bertalanffy (vonB) growth model parameter estimation using an extensive simulation study. We further demonstrate methods by applying the two best-performing and the most popular methods to estimate the vonB model parameters for American plaice (Hippoglossoides platessoides) in NAFO Divisions 3LNO. Our simulations demonstrated that mis-specifying one or more of the three sampling components increases the RRMSEs, and this effect is magnified when the age distribution is incorrectly specified. The optimal approach for data based on LSAS is the empirical proportion approach, and we recommend this method for growth parameter estimation based on LSAS data.

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Li, Shuying, Shaowei Wang, and Qiang Li. "Joint Posterior Probability Active Learning for Hyperspectral Image Classification." Remote Sensing 15, no. 16 (August 9, 2023): 3936. http://dx.doi.org/10.3390/rs15163936.

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Active learning (AL) is an approach that can reduce the dependence on the labeled set significantly. However, most current active-learning methods are only concerned with the first two columns of the posterior probability matrix during the sampling phase. When the difference between the first and second-largest posterior probabilities of several samples is proximate, these approaches fail to distinguish them further. To improve these deficiencies, we propose an active-learning algorithm, joint posterior probabilistic active learning combined with conditional random field (JPPAL_CRF). In the active-learning sampling phase, a new sampling decision function is built by jointing all the information in the posterior probability matrix. By doing so, the variability between different samples is refined, which makes the selected samples more meaningful for classification. Then, a conditional random field (CRF) approach is applied to mine the regional spatial information of the hyperspectral image and optimize the classification results. Experiments on two common hyperspectral datasets validate the effectiveness of JPPAL_CRF.

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Jalali, Yousef, Hossein Eskandari, Ahmad Borjali, Faramarz Sohrabi, and Mohammad Asgari. "The identity of Iranian male adolescents in the context of master narrative of their lives: A qualitative study." Shenakht Journal of Psychology and Psychiatry 8, no. 5 (November 27, 2021): 13–26. http://dx.doi.org/10.32598/shenakht.8.5.13.

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Introduction: There is not in-depth knowledge about the master narrative of identity and its quiddity in current generation of Iranian adolescents. Aim: The aim of this study was to identify and validate the master narrative model of identity of Iranian adolescents. Method: This study was a basic research with a mixed approach. In the qualitative phase, the population consisted of male adolescents aged 15-20 years old, as well as psychologists and sociologists in Tehran in 2020. Nineteen adolescents were selected by convenience sampling and six specialists by purposive sampling. In the quantitative phase, the population consisted of adolescents aged 15-20 years old in Tehran in 2020, from which 218 people were selected by convenience sampling. In the qualitative phase, data were collected through the life story interview (McAdams, 1995) and in the quantitative phase by a researcher-made questionnaire. In the qualitative phase, data were analyzed through the content analysis method and in the quantitative phase through the confirmatory factor analysis. Results: The results of content analysis in addition to factor analysis indicated the master narrative model of adolescents includes components such as family belonging, adherence to religious values and obedience to parents. Results of second-order factor analysis also indicated the obedience to parents (Z=1.32) has the most contribution in the model. Conclusion: Despite the development of modern values in Iranian society, traditional values still play a significant role in the master narrative of identity of Iranian male adolescents.

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Zhao, Yuan, Bingliang Hu, Zhen-An He, Wenjia Xie, and Xiaohui Gao. "Generation and coherent detection of QPSK signal using a novel method of digital signal processing." Modern Physics Letters B 32, no. 04 (February 9, 2018): 1850103. http://dx.doi.org/10.1142/s0217984918501038.

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We demonstrate an optical quadrature phase-shift keying (QPSK) signal transmitter and an optical receiver for demodulating optical QPSK signal with homodyne detection and digital signal processing (DSP). DSP on the homodyne detection scheme is employed without locking the phase of the local oscillator (LO). In this paper, we present an extracting one-dimensional array of down-sampling method for reducing unwanted samples of constellation diagram measurement. Such a novel scheme embodies the following major advantages over the other conventional optical QPSK signal detection methods. First, this homodyne detection scheme does not need strict requirement on LO in comparison with linear optical sampling, such as having a flat spectral density and phase over the spectral support of the source under test. Second, the LabVIEW software is directly used for recovering the QPSK signal constellation without employing complex DSP circuit. Third, this scheme is applicable to multilevel modulation formats such as M-ary PSK and quadrature amplitude modulation (QAM) or higher speed signals by making minor changes.

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Jørgensen, J. S., and E. Y. Sidky. "How little data is enough? Phase-diagram analysis of sparsity-regularized X-ray computed tomography." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2043 (June 13, 2015): 20140387. http://dx.doi.org/10.1098/rsta.2014.0387.

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We introduce phase-diagram analysis, a standard tool in compressed sensing (CS), to the X-ray computed tomography (CT) community as a systematic method for determining how few projections suffice for accurate sparsity-regularized reconstruction. In CS, a phase diagram is a convenient way to study and express certain theoretical relations between sparsity and sufficient sampling. We adapt phase-diagram analysis for empirical use in X-ray CT for which the same theoretical results do not hold. We demonstrate in three case studies the potential of phase-diagram analysis for providing quantitative answers to questions of undersampling. First, we demonstrate that there are cases where X-ray CT empirically performs comparably with a near-optimal CS strategy, namely taking measurements with Gaussian sensing matrices. Second, we show that, in contrast to what might have been anticipated, taking randomized CT measurements does not lead to improved performance compared with standard structured sampling patterns. Finally, we show preliminary results of how well phase-diagram analysis can predict the sufficient number of projections for accurately reconstructing a large-scale image of a given sparsity by means of total-variation regularization.

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Ahmed, Mohammed, Cyrus Daneshvar, and David Breen. "Routine neck ultrasound by respiratory physicians in the diagnosis and staging of patients with lung cancer and mediastinal lymphadenopathy: a prospective pilot study." ERJ Open Research 6, no. 1 (January 2020): 00180–2019. http://dx.doi.org/10.1183/23120541.00180-2019.

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IntroductionCervical lymphadenopathy in lung cancer indicates advanced disease. The presence of mediastinal lymphadenopathy is commonly associated with involvement of neck lymph nodes and some studies suggest routine neck ultrasound (NUS) in this group of patients. We conducted a two-phase study looking at training a respiratory physician to perform ultrasound-guided neck lymph node aspiration in patients with suspected lung cancer.MethodsIn the first phase of the study, one of the authors underwent training in NUS according to predetermined criteria. The adequacy of sampling was prospectively recorded. In the second phase, consecutive patients with suspected lung cancer and mediastinal lymphadenopathy underwent NUS and sampling of abnormal lymph nodes. The outcomes were the adequacy of samples for pathological analysis and molecular analysis, prevalence of cervical lymphadenopathy, and change in stage.ResultsFollowing the period of training, 35 patients underwent neck node sampling with an overall adequacy of 88.6% (95% CI 78.1–99.1%). Cervical lymph node involvement was confirmed in 13 out of 30 patients with lung cancer (43.3%, 95% CI 25.5–62.6%). Further immunohistochemistry and molecular studies were possible in all patients when it was required (nine cases). NUS led to nodal upstaging in four out of 30 (13.3%) cases.ConclusionTraining a respiratory physician to perform NUS and needle sampling to an acceptable level is feasible. Benefits of embedding this procedure in lung cancer diagnosis and pathway staging need to be explored in further studies.

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Journal articles on the topic 'Second phase sampling'

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