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Parameter K (parameter + k)
Selected AbstractsA comparison of techniques for hydrograph recession analysisHYDROLOGICAL PROCESSES, Issue 3 2004Joko Sujono Abstract A comparison between commonly used techniques for hydrograph recession analysis, namely the semi-logarithmic plot of a single recession segment, the master recession and a relatively new approach based on wavelet transform was carried out. These methods were applied to a number of flood hydrograph events of two catchments in West Java, Indonesia. The results show that all the methods tested produce reasonable and comparable results. However, problems arise in the semi-logarithmic plot and the master recession, i.e. determining the recession parameter K is not an easy task especially where the plotted data on a semi-logarithmic plot is not a linear but a curved line. On a curved line, the end of direct flow or starting point of baseflow is not clear and it is quite difficult to identify. Hence, the best line as a basis for computing the recession parameter K becomes uncertain. The wavelet transform approach, however, produces promising results and minimizes a number of problems associated with hydrograph recession analysis. The end of direct flow and the location of the baseflow component are easily determined through the wavelet maps. Copyright © 2004 John Wiley & Sons, Ltd. [source] Measures, perceptions and scaling patterns of aggregated species distributionsECOGRAPHY, Issue 1 2010Cang Hui Non-random (aggregated) species distributions arise from habitat heterogeneity and nonlinear biotic processes. A comprehensive understanding of the concept of aggregation, as well as its measurement, is pivotal to our understanding of species distributions and macroecological patterns. Here, using an individual-based model, we analyzed opinions on the concept of aggregation from the public and experts (trained ecologists), in addition to those calculated from a variety of aggregation indices. Three forms of scaling patterns (logarithmic, power-law and lognormal) and four groups of scaling trajectories emerged. The experts showed no significant difference from the public, although with a much lower deviation. The public opinion was partially influenced by the abundance of individuals in the spatial map, which was not found in the experts. With the increase of resolution (decrease of grain), aggregation indices showed a general trend from significantly different to significantly similar to the expert opinion. The over-dispersion index (i.e. the clumping parameter k in the negative binomial distribution) performed, at certain scales, as the closest index to the expert opinion. Examining performance of aggregation measures from different groups of scaling patterns was proposed as a practical way of analyzing spatial structures. The categorization of the scaling patterns of aggregation measures, as well as their over- and in-sensitivity towards spatial structures, thus not only provides a potential solution to the modifiable areal unit problem, but also unveils the interrelationship among the concept, measures and perceptions of aggregated species distributions. [source] Soil organic carbon stocks in Flemish grasslands: how accurate are they?GRASS & FORAGE SCIENCE, Issue 4 2004I. Mestdagh Abstract Articles 3·3 and 3·4 of the Kyoto protocol provide Annex I countries the possibility to reduce greenhouse gas emissions through the sequestration of carbon (C) in their terrestrial ecosystems. For such accounting, the 1990 flux is needed and, therefore, a correct knowledge of the baseline (1990) C stocks is necessary. In addition, a correct methodology should be used to investigate the capacity of ecosystems to sequester C through changes in land use or management by the end of the first commitment period (2008,2012). At national and regional scales, formulation of baseline C stocks in terrestrial ecosystems is difficult and uncertain. Differences in method of analysis, sampling depth of soil, lack of sufficient C data and the necessity to extrapolate C data to total soil organic C stocks, provide problems when comparing databases with each other. In this study, three extrapolation models were compared with the classical layer-based method to determine the model with the best fit. The model with the best predictions, in relation to the classical layer-based model, uses recent soil C profiles for estimating the parameter k, which represents the decrease in the proportion of soil organic C with depth, and for extrapolating the C data available for 1990 and 2000 to a depth of 1 m. The other two models gave large underestimates. [source] Simplified estimation of seismically induced settlementsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2003E. Vincens Abstract This paper proposes a predictive expression of settlements for a dry sand deposit overlying a bedrock and subjected to a seismic motion. The proposed formula combines geometrical and mechanical properties of the soil profile with classical characteristics of the input motion. One of the main concepts developed herein consists in regarding the input motion and the dynamical response as samples of random processes; another key concept consists in the common densification curve from Sawicki. The model introduces a parameter k identified by means of an extensive set of accelerograms. The main advantage of the proposed method consists in allowing fast comparisons of earthquake induced settlements for different soil and motion characteristics and therefore quantifying the damage power of a time-history input motion. Copyright © 2003 John Wiley & Sons, Ltd. [source] Determination of Weibull parameters for wind energy analysis of ,zmir, TurkeyINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2002K. Ulgen Abstract In this study, the two Weibull parameters of the wind speed distribution function, the shape parameter k (dimensionless) and the scale parameter c (ms,1), were computed from the wind speed data for ,zmir. Wind data, consisting of hourly wind speed records over a 5-year period, 1995,1999, were measured in the Solar/Wind-Meteorological Station of the Solar Energy Institute at Ege University. Based on the experimental data, it was found that the numerical values of both Weibull parameters (k and c) for ,zmir vary over a wide range. The yearly values of k range from 1.378 to 1.634 with a mean value of 1.552, while those of c are in the range of 2.956,3.444 with a mean value of 3.222. The average seasonal Weibull distributions for ,zmir are also given. The wind speed distributions are represented by Weibull distribution and also by Rayleigh distribution, with a special case of the Weibull distribution for k=2. As a result, the Weibull distribution is found to be suitable to represent the actual probability of wind speed data for ,zmir (at annual average wind speeds up to 3 ms,1). Copyright © 2002 John Wiley & Sons, Ltd. [source] Timing of Depolarization and Contraction in the Paced Canine Left Ventricle:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2003Experiment, Model Introduction: For efficient pump function, contraction of the heart should be as synchronous as possible. Ventricular pacing induces asynchrony of depolarization and contraction. The degree of asynchrony depends on the position of the pacing electrode. The aim of this study was to extend an existing numerical model of electromechanics in the left ventricle (LV) to the application of ventricular pacing. With the model, the relation between pacing site and patterns of depolarization and contraction was investigated. Methods and Results: The LV was approximated by a thick-walled ellipsoid with a realistic myofiber orientation. Propagation of the depolarization wave was described by the eikonal-diffusion equation, in which five parameters play a role: myocardial and subendocardial velocity of wave propagation along the myofiber cm and ce; myocardial and subendocardial anisotropy am and ae; and parameter k, describing the influence of wave curvature on wave velocity. Parameters cm, ae, and k were taken from literature. Parameters am and ce were estimated by fitting the model to experimental data, obtained by pacing the canine left ventricular free wall (LVFW). The best fit was found with cm= 0.75 m/s, ce= 1.3 m/s, am= 2.5, ae= 1.5, and k= 2.1 × 10,4 m2/s. With these parameter settings, for right ventricular apex (RVA) pacing, the depolarization times were realistically simulated as also shown by the wavefronts and the time needed to activate the LVFW. The moment of depolarization was used to initiate myofiber contraction in a model of LV mechanics. For both pacing situations, mid-wall circumferential strains and onset of myofiber shortening were obtained. Conclusion: With a relatively simple model setup, simulated depolarization timing patterns agreed with measurements for pacing at the LVFW and RVA in an LV. Myocardial cross-fiber wave velocity is estimated to be 0.40 times the velocity along the myofiber direction (0.75 m/s). Subendocardial wave velocity is about 1.7 times faster than in the rest of the myocardium, but about 3 times slower than as found in Purkinje fibers. Furthermore, model and experiment agreed in the following respects. (1) Ventricular pacing decreased both systolic pressure and ejection fraction relative to natural sinus rhythm. (2) In early depolarized regions, early shortening was observed in the isovolumic contraction phase; in late depolarized regions, myofibers were stretched in this phase. Maps showing timing of onset of shortening were similar to previously measured maps in which wave velocity of contraction appeared similar to that of depolarization. (J Cardiovasc Electrophysiol, Vol. 14, pp. S188-S195, October 2003, Suppl.) [source] A new upper bound on the cyclic chromatic number,JOURNAL OF GRAPH THEORY, Issue 1 2007O. V. Borodin Abstract A cyclic coloring of a plane graph is a vertex coloring such that vertices incident with the same face have distinct colors. The minimum number of colors in a cyclic coloring of a graph is its cyclic chromatic number ,c. Let ,* be the maximum face degree of a graph. There exist plane graphs with ,c = ,3/2 ,*,. Ore and Plummer [5] proved that ,c , 2, ,*, which bound was improved to ,9/5, ,*, by Borodin, Sanders, and Zhao [1], and to ,5/3,,*, by Sanders and Zhao [7]. We introduce a new parameter k*, which is the maximum number of vertices that two faces of a graph can have in common, and prove that ,c , max {,* + 3,k* + 2, ,* + 14, 3, k* + 6, 18}, and if ,* , 4 and k* , 4, then ,c , ,* + 3,k* + 2. © 2006 Wiley Periodicals, Inc. J Graph Theory [source] Blind equalization of space-time-turbo trellis coded/continuous phase modulation over Rician fading channelsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2004Osman N. Ucan In this paper, to improve bit error performance and bandwidth efficiency, we combine space-time block codes (STBC), turbo trellis codes and continuous phase modulation and denote space-time-turbo trellis coded/continuous phase modulation (ST-TTC/CPM). For high data transmission over wireless fading channels, STBC provide the maximal possible diversity advantage for multiple decoding algorithms. We present continuous phase modulation (CPM) for ST-TTC signals, since CPM provides low-spectral occupancy and is suitable for power and bandwidth-limited channels. In our model, to utilize STBC efficiently, we need to estimate the channel parameters, which influence the signals having continuity property. Therefore, we develop a blind maximum likelihood channel estimation algorithm for signals propagating through a Rician fading channel. Here, Baum-Welch (BW) algorithm, based on hidden Markov model (HMM), is modified to provide computationally efficient channel parameter estimation. We also investigate the performance of ST-TTC/CPM in the case of no channel state information (CSI) for various Rician parameters K and Doppler frequency. Copyright © 2004 AEI. [source] Lipophilicity determination of N -( benzothiazol-2-yl )-,-amino alkyl phosphonic diesters by RP-HPLC and RP-HPTLCCHINESE JOURNAL OF CHEMISTRY, Issue 6 2000Luig Zhang Abstract Using methanol-water mixtures as the mobile phase, the chromatographic retention parameters k' and Rf were determined by reversed-phase high-performance liquid chromatography (RP-HPLC) and reversed-phase high-performance thin-layer chromatography (RP-HPTLC) for N- (benzothiazol-2-yl)-,-amino alkyl phosphoric diesters and the correlation with lipophilicity parameter (Clog P) was established. Log Kw values obtained from RP-HPLC and Rm values obtained from RP-HPTLC can be used to evaluate the lipophilicity of this kind of compounds. Chromatographic method is a good alternative for lipophilicity measurement. [source] | ||||||||||