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Matrix Approach (matrix + approach)
Selected AbstractsVoltinism flexibility of a riverine dragonfly along thermal gradientsGLOBAL CHANGE BIOLOGY, Issue 3 2008ERIK BRAUNE Abstract Potential effects of future warming should be reflected in life history patterns of aquatic organisms observed in warmer climates or in habitats that are different in ambient temperature. In the special case of the dragonfly Gomphus vulgatissimus (L.) (Odonata: Gomphidae) previous research suggests that voltinism decreases from south to north. We analysed data on voltinism from 11 sample sites along a latitudinal gradient from about 44°N to 53°N, comprising small streams to medium-sized rivers. Furthermore, to simulate different conditions and to allow projections for future climate change scenarios, we developed a population dynamic model based on a projection matrix approach. The parameters of the model are dependent on temperature and day length. Our field results indicate a decrease in voltinism along the latitudinal gradient from southern to northern Europe and a corresponding increase of voltinism with higher temperatures. An increase in voltinism with width of the running water implies an effect of varying habitat temperature. Under the impact of global warming, our model predicts an increased development speed, particularly in the northern part of the latitudinal gradient, an extension of the northern range limit and changes in phenology of G. vulgatissimus, leading to an extension of the flight season in certain regions along the gradient. [source] Impact of Simulation Model Solver Performance on Ground Water Management ProblemsGROUND WATER, Issue 5 2008David P. Ahlfeld Ground water management models require the repeated solution of a simulation model to identify an optimal solution to the management problem. Limited precision in simulation model calculations can cause optimization algorithms to produce erroneous solutions. Experiments are conducted on a transient field application with a streamflow depletion control management formulation solved with a response matrix approach. The experiment consists of solving the management model with different levels of simulation model solution precision and comparing the differences in optimal solutions obtained. The precision of simulation model solutions is controlled by choice of solver and convergence parameter and is monitored by observing reported budget discrepancy. The difference in management model solutions results from errors in computation of response coefficients. Error in the largest response coefficients is found to have the most significant impact on the optimal solution. Methods for diagnosing the adequacy of precision when simulation models are used in a management model framework are proposed. [source] ,Part of the family': sources of job satisfaction amongst a group of community-based dementia care workersHEALTH & SOCIAL CARE IN THE COMMUNITY, Issue 2 2004Tony Ryan MA BSc Abstract The development of community-based services for people with dementia brings new challenges for health and social care providers, not least that of sustaining an enthusiastic workforce who are motivated to provide care and support under potentially isolating and difficult conditions. The present paper, based on interview data gathered from a group of community-based dementia care workers, seeks to identify their sources of job satisfaction and reward. Interviews were conducted with seven workers at two points in time and the data were analysed using a case by theme matrix approach. The results indicate that there were high levels of job satisfaction amongst the group, which were enhanced by several factors, including: good organisational support; day-to-day autonomy; the ability to maintain relationships with people with dementia and their families; and staffs' feelings of contributing to and improving the status and quality of life of people with dementia. Implications for workforce development are briefly considered. [source] A forward-only recursion algorithm for MAP decoding of linear block codesINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2002Hans-Jürgen Zepernick Abstract The evolution of digital mobile communications along with the increase of integrated circuit complexity has resulted in frequent use of error control coding to protect information against transmission errors. Soft decision decoding offers better error performance compared to hard decision decoding but on the expense of decoding complexity. The maximum a posteriori (MAP) decoder is a decoding algorithm which processes soft information and aims at minimizing bit error probability. In this paper, a matrix approach is presented which analytically describes MAP decoding of linear block codes in an original domain and a corresponding spectral domain. The trellis-based decoding approach belongs to the class of forward-only recursion algorithms. It is applicable to high rate block codes with a moderate number of parity bits and allows a simple implementation in the spectral domain in terms of storage requirements and computational complexity. Especially, the required storage space can be significantly reduced compared to conventional BCJR-based decoding algorithms. Copyright © 2002 John Wiley & Sons, Ltd. [source] Exponential H, filtering for switched linear systems with interval time-varying delayINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 5 2009Dong Wang Abstract This paper deals with the problem of exponential H, filtering for a class of continuous-time switched linear system with interval time-varying delay. The time delay under consideration includes two cases: one is that the time delay is differentiable and bounded with a constant delay-derivative bound, whereas the other is that the time delay is continuous and bounded. Switched linear filters are designed to ensure that the filtering error systems under switching signal with average dwell time are exponentially stable with a prescribed H, noise attenuation level. Based on the free-weighting matrix approach and the average dwell technology, delay-dependent sufficient conditions for the existence of such a filter are derived and formulated in terms of linear matrix inequalities (LMIs). By solving that corresponding LMIs, the desired filter parameterized matrices and the minimal average dwell time are obtained. Finally, two numerical examples are presented to demonstrate the effectiveness of the developed results. Copyright © 2008 John Wiley & Sons, Ltd. [source] A slow-wave structure with Koch fractal slot loopsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2002Jung-Hyo Kim Abstract In this Letter, a Koch slot loop in the ground plane has been utilized to obtain slow-wave characteristics, and its electrical performances are analyzed with the use of the ABCD matrix approach. The validity of this approach has been verified through experimental results, and this technique was then applied to microstrip patch antennas in order to obtain a small antenna size. The cross-sectional areas of this type of antenna are 47% to 65% smaller than those of conventional square patches. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 87,88, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10381 [source] Probing cosmology and galaxy cluster structure with the Sunyaev,Zel'dovich decrement versus X-ray temperature scaling relationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009Cien Shang ABSTRACT Scaling relations among galaxy cluster observables, which will become available in large future samples of galaxy clusters, could be used to constrain not only cluster structure, but also cosmology. We study the utility of this approach, employing a physically motivated parametric model to describe cluster structure and applying it to the expected relation between the Sunyaev,Zel'dovich decrement (S,) and the emission-weighted X-ray temperature (Tew). The slope and normalization of the entropy profile, the concentration of the dark matter potential, the pressure at the virial radius and the level of non-thermal pressure support as well as the mass and redshift dependence of these quantities are described by free parameters. With a suitable choice of fiducial parameter values, the cluster model satisfies several existing observational constraints. We employ a Fisher matrix approach to estimate the joint errors on cosmological and cluster structure parameters from a measurement of S, versus Tew in a future survey. We find that different cosmological parameters affect the scaling relation differently: predominantly through the baryon fraction (,m and ,b), the virial overdensity (w0 and wa for low- z clusters) and the angular diameter distance (w0 and wa for high- z clusters; ,DE and h). We find that the cosmology constraints from the scaling relation are comparable to those expected from the number counts (dN/dz) of the same clusters. The scaling-relation approach is relatively insensitive to selection effects and it offers a valuable consistency check; combining the information from the scaling relation and dN/dz is also useful to break parameter degeneracies and help disentangle cluster physics from cosmology. Our work suggests that scaling relations should be a useful component in extracting cosmological information from large future cluster surveys. [source] Applicability of electrical resistivity tomography monitoring to coarse blocky and ice-rich permafrost landformsPERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2009C. Hilbich Abstract The inversion and interpretation of electrical resistivity tomography (ERT) data from coarse blocky and ice-rich permafrost sites are challenging due to strong resistivity contrasts and high contact resistances. To assess temporal changes during ERT monitoring (ERTM), corresponding inversion artefacts have to be separated from true subsurface changes. Appraisal techniques serve to analyse an ERTM data set from a rockglacier, including synthetic modelling, the depth of investigation index technique and the so-called resolution matrix approach. The application of these methods led step by step to the identification of unreliable model regions and thus to the improvement in interpretation of temporal resistivity changes. An important result is that resistivity values of model regions with strong resistivity contrasts and highly resistive features are generally of critical reliability, and resistivity changes within or below the ice core of a rockglacier should therefore not be interpreted as a permafrost signal. Conversely, long-term degradation phenomena in terms of warming of massive ground ice at the permafrost table are detectable by ERTM. Copyright © 2009 John Wiley & Sons, Ltd. [source] Optical properties of delta poly-type quasiregular dielectric structures made of porous siliconPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007V. Agarwal Abstract To investigate the reflection of light in quasi-regular dielectrics, we study here the optical properties of porous-silicon-based Fibonacci, Thue-Morse and Period Doubling heterostructures. The multilayered systems are fabricated in such a way that each element in the two-block substitutional sequence has a poly-type structure. Both delta-like and traditional configurations are considered. The results for the optical transmittance are analyzed and compared with the classical periodic structure. Numerical simulation for the transmittance along the lines of the transfer matrix approach is also presented. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Two-step mean-field renormalization group results for the large square Ising clustersPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003G. Kamieniarz Abstract A transfer matrix approach has been worked out to test the predictions of the improved three-step mean-field renormalization group approach to square Ising clusters with linear size up to L = 11. Performing the asymptotic analysis, the convergence of the finite-size critical couplings and the critical exponents towards the exact values is shown. [source] Simultaneous measurement of 13C- and 15N-isotopic enrichments of threonine by mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009Jean-Philippe Godin Under conditions of high isotopic dilution, e.g. in a tracer study, the ability to determine accurately and quantitatively small variations in isotopic enrichments of differently labelled chemical compounds (e.g. 13C and 15N in threonine) in a single run by gas chromatography/mass spectrometry (GC/MS) is desirable but remains a technological challenge. Here, we report a new, rapid and simple GC/MS method for simultaneously measuring the isotopic enrichments of doubly labelled threonine ([U13C] and 15N) with isotopic enrichment lower than 1.5 Molar Percent Excess (MPE). The long-term reproducibility measured was around 0.09 MPE for both tracers (throughout a 6 week period). The intra-day repeatability was lower than 0.05 and 0.06 MPE for [U13C]-Thr and 15N-Thr, respectively. To calculate both isotopic enrichments, two modes of calculations were used: one based on work by Rosenblatt et al. in 1992 and the other one using a matrix approach. Both methods gave similar results (ANOVA, P >0.05) with close precision for each mode of calculation. The GC/MS method was then used to investigate the differential utilization of threonine in different organs according to its route of administration in minipigs after administration of both tracers. In plasma samples, the lowest isotopic enrichment measured between two successive time points was at 0.01 and 0.02 MPE for [U13C]-Thr and 15N-Thr, respectively. Moreover, the accuracy of GC/MS 13C-isotopic enrichment measured was validated by analyzing the same plasma samples by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Statistical analysis showed that both techniques gave the same results (ANOVA, P >0.05). This new GC/MS method offers the possibility to measure 13C- and 15N-isotopic enrichments with higher throughput, and using a lower amount of sample, than using GC/C/IRMS. Copyright © 2009 John Wiley & Sons, Ltd. [source] A construct validity study of clinical competence: A multitrait multimethod matrix approachTHE JOURNAL OF CONTINUING EDUCATION IN THE HEALTH PROFESSIONS, Issue 1 2010Lubna Baig MBBS, PhD Managing Director, Professor of Community Medicine Abstract Introduction: The purpose of the study was to adduce evidence for estimating the construct validity of clinical competence measured through assessment instruments used for high-stakes examinations. Methods: Thirty-nine international physicians (mean age = 41 + 6.5 y) participated in high-stakes examination and 3-month supervised clinical practice to determine the practice readiness of physicians. Three traits,doctor,patient relationship, clinical competence, and communication skills,were assessed with objective structured clinical examinations, in-training evaluation reports, and clinical assessments. These traits were intercorrelated in a multitrait multimethod matrix (MTMM). Results: The reliability of assessments ranged from moderate to high (Cronbach's ,: 0.58,0.98; Ep2 = 0.79). There is evidence for both convergent and divergent validity for clinical competence, followed by doctor,patient relationships, and communications (validity coefficients = 0.12,0.85). The correlations between the same methods but different traits indicate that there is substantial method specificity in the assessment accounting for nearly one-quarter of the variance (23.7%). Discussion: There is evidence for the construct validity of all 3 traits across 3 methods. The MTMM approach, currently underutilized, could be used to estimate the degree of evidence for validating complex constructs, such as clinical competence. [source] | ||||||||||||||||