Intervals Of Different Length Research Articles

Influence of External Factors on the Strength of Firefighting Hoses Used in Fire Protection Units

Aim: The purpose of this article is to review information on firefighting hoses in terms of their division and the materials used in their production, and to determine if and how external factors affect their strength and durability. Introduction: Firefighting hoses are one of the most important products of technical equipment of Fire Protection Units. Since they are an indispensable element during rescue and firefighting operations, conducting research on the strength of fire hoses is needed and extremely important from the point of view of fire protection. Project and methods: Technological advances in the area of using various types of materials for fire hoses over time have had (and continue to have) a significant impact on the undertaking of rescue and firefighting operations, the speed with which these operations are carried out, as well as their effectiveness. Therefore, at the beginning of the article, a historical outline of the fire hoses used for firefighting in various countries around the world over the years was made. In the following part of the article, the influence of external factors on the adhesive strength of firefighting hoses used in fire protection units in Poland was analysed. The effect of exposure to a 3% foam solution of a fire extinguishing agent on hose tape samples placed in this solution was tested, depending on the time of direct contact of the samples with this agent. The effect of UV exposure (under wetting and drying conditions) on the hose tape samples was also studied, with time intervals of different lengths. Results: When testing the exposure of the hose tape samples to UV light (for 90 minutes, at 38 ± 3°C, without water spray, followed by water exposure for 30 minutes, at 50 ± 10% humidity), decreasing trends were observed for the average values of delamination strengths. Tests were also made on a series of samples exposed to a 3% solution of aqueous foam extinguishing agent on the hose tape, both externally and internally. Declining trends were observed for the mean values of adhesive strengths (after 3 and 6 weeks). The impact of factors such as exposure to UV radiation, as well as the impact of the foam extinguishing agent solution negatively affects the hose tape, reducing its strength. The article was prepared on the basis of the authors’ own research results, as well as available sources, both national and foreign, based on the available literature on the raised issues. Keywords: firefighting hose, fire hose strength, adhesion, UV, foam extinguishing agent

Determining interval lengths for fuzzy time series forecasting model based on index of fuzzy sets by combining hedge algebra and particle swarm optimization

Researchers frequently use fuzzy time series (FTS) forecasting models to estimate future values since they do not rely on the same rigid assumptions as traditional forecasting techniques. There are generally four factors that determine the performance of the FTS forecasting model (1) determining the length of intervals in the universe of discourse, (2) fuzzification rules or feature representation of crisp time series, (3) establishing fuzzy relation groups (FRGs) and (4) creating defuzzification rule to get crisp forecasted value. Considering the first factor and the fourth factor, we propose the hybrid FTS forecasting model combining particle swarm optimization (PSO) and hedge algebra (HA) to improve forecasting accuracy. Where the hedge algebra is utilized as a tool for partitioning the universe of discourse into intervals of different lengths. Then, the times series data are fuzzified into fuzzy sets, the fuzzy relationship groups are established and forecasting output value based on the index of fuzzy sets is calculated. Ultimately, the suggested model collaborates with PSO to obtain the optimal intervals determined by HA. To test the proposed model, we conduct a simulated study on two widely used real-time series and compare the performance with some recently developed models. Error statistics, such as MSE and RMSE show that the proposed model performs better than the comparing models.

Consistent development patterns

Traditional claim estimation in general insurance works with accident year cohorts and development patterns. For the impending International Financial Reporting Standard (IFRS) 17 Insurance Contracts and often for reinsurance purposes, claim estimates must be split by contract year. This paper proposes to add contract year as a cohort classifier and to adjust the development patterns accordingly. To this end, we use the continuous time models of Hesselager and Norberg. Having contract year as an additional cohort classifier, display of claim estimates by contract year and/or accident year becomes a simple matter of summation across the appropriate dimensions. The continuous time model also enables us to derive mutually consistent development patterns for discrete time intervals of different length, such as years and quarters. In addition to delivering consistent development patterns in discrete time, continuous time modelling offers the advantage of requiring only a fixed number of model parameters. Although most of the derivations in this paper are explained in terms of claim numbers, the mechanics can also be applied to claim payments.

A unified system for tree- and stand-level predictions

The unified system developed in this study comprises two components, one to predict survival and the other to predict diameter, both at tree and stand levels. The tree survival model defaults to the stand survival model when tree diameter reaches a certain value. Similarly, the tree diameter growth model defaults to the quadratic mean diameter model when tree diameter is equal to quadratic mean diameter. The annual growth approach was used to accommodate growth intervals of different lengths. Parameters of the unified system can be estimated together (Simultaneous Estimation) or separately in two phases (Sequential Estimation). Also investigated was the Disaggregation method in which tree attributes (survival probabilities and diameters) were adjusted to match outputs from the stand-level models (number of trees and basal area per unit area).Results indicated that, overall, the Disaggregation approach gave a better performance than did the Unadjusted approach. On the other hand, the Sequential Estimation narrowly surpassed the Simultaneous Estimation method (overall rank of 1.00 versus 1.10). Parameters of the unified system should be estimated by use of the Sequential Estimation method because it is a simpler method which involves only a subset of the parameters at each estimation phase.

Composite Estimators for Forest Growth Derived from Symmetric, Varying-Length Observation Intervals

Estimates of growth or change in a forest population parameter for a specific length of time, such as cubic meters of wood per hectare per year, are often made from sample observation intervals of different lengths of time. For instance, a basic building block of growth estimators in forest inventory systems is often the annual mean of the first differences of all observations for a particular year, regardless of observation interval length. The aggregate differences between successive observations on re-measured forest sample plots can be viewed as a linear combination, while forest growth is usually assumed to be non-linear. Bias can be assumed to exist whenever a linear combination is used to estimate a specific segment of an underlying non-linear trend. The amount of bias will depend upon the relationship of the intended estimation interval relative to the set of observation intervals. Here, three specific segments, relative to each year of interest, form the bases for a standard set of three estimands. Bias-ratio-adjusted composite estimators for use with observations made on alternative sets of symmetric interval lengths are compared in a simulation against this standard set of estimands. The first estimand has a one-year basis, the second has a five-year mid-interval basis, and the third has a five-year end-of-period basis. For the first and second bases, the initial results clearly show a logical ordering of bias and mean-squared error by observation interval length relative to the target interval length. As expected, some deviance from these clear trends are shown for the end-of-period basis. In the presence of three simple distributions of symmetric measurement intervals, the bias-ratio adjustments and subsequent composite estimators are shown to usually be effective in reducing bias and mean-squared error, while being most obviously effective for the most disparate distribution of intervals and for the end-of-period basis.

Time processing in children with mathematical difficulties

Time processing is a fundamental ability in everyday living that improves with age. It has been suggested that time processing may be related to the representation of quantity and therefore with mathematical difficulties, but the relationship and, in particular, the implications of different time intervals are still unclear. In the present study, we investigated the relationship between mathematical abilities and the ability to reproduce time intervals of different lengths to test whether children with mathematical difficulties would also exhibit temporal impairment especially when long time intervals are involved. Twenty children with mathematical difficulties and twenty matched children without difficulties were administered a time reproduction task using short standard intervals (500ms, 1000ms, and 1500ms) and long standard intervals (4s, 9s, and 14s). Results showed lower temporal abilities in children with mathematical difficulties, which were particularly evident when the standard intervals were long, thus supporting the hypotheses of a relationship between mathematical and time processing abilities and of distinct systems to process time.

Longitudinal Study of Mammographic Density Measures That Predict Breast Cancer Risk.

Background: After adjusting for age and body mass index (BMI), mammographic measures-dense area (DA), percent dense area (PDA), and nondense area (NDA)-are associated with breast cancer risk. Our aim was to use longitudinal data to estimate the extent to which these risk-predicting measures track over time.Methods: We collected 4,320 mammograms (age range, 24-83 years) from 970 women in the Melbourne Collaborative Cohort Study and the Australian Breast Cancer Family Registry. Women had on average 4.5 mammograms (range, 1-14). DA, PDA, and NDA were measured using the Cumulus software and normalized using the Box-Cox method. Correlations in the normalized risk-predicting measures over time intervals of different lengths were estimated using nonlinear mixed-effects modeling of Gompertz curves.Results: Mean normalized DA and PDA were constant with age to the early 40s, decreased over the next two decades, and were almost constant from the mid-60s onward. Mean normalized NDA increased nonlinearly with age. After adjusting for age and BMI, the within-woman correlation estimates for normalized DA were 0.94, 0.93, 0.91, 0.91, and 0.91 for mammograms taken 2, 4, 6, 8, and 10 years apart, respectively. Similar correlations were estimated for the age- and BMI-adjusted normalized PDA and NDA.Conclusions: The mammographic measures that predict breast cancer risk are highly correlated over time.Impact: This has implications for etiologic research and clinical management whereby women at increased risk could be identified at a young age (e.g., early 40s or even younger) and recommended appropriate screening and prevention strategies. Cancer Epidemiol Biomarkers Prev; 26(4); 651-60. ©2017 AACR.

Experimental reduction in interaction intensity strongly affects biotic selection.

The link between biotic interaction intensity and strength of selection is of fundamental interest for understanding biotically driven diversification and predicting the consequences of environmental change. The strength of selection resulting from biotic interactions is determined by the strength of the interaction and by the covariance between fitness and the trait under selection. When the relationship between trait and absolute fitness is constant, selection strength should be a direct function of mean population interaction intensity. To test this prediction, we excluded pollinators for intervals of different length to induce five levels of pollination intensity within a single plant population. Pollen limitation (PL) increased from 0 to 0.77 across treatments, accompanied by a fivefold increase in the opportunity for selection. Trait-fitness covariance declined with PL for number of flowers, but varied little for other traits. Pollinator-mediated selection on plant height, corolla size, and spur length increased by 91%, 34%, and 330%, respectively, in the most severely pollen-limited treatment compared to open-pollinated plants. The results indicate that realized biotic selection can be predicted from mean population interaction intensity when variation in trait-fitness covariance is limited, and that declines in pollination intensity will strongly increase selection on traits involved in the interaction.

Geostatistical Data Fusion of Multiple Type Observations to Improve Land Subsidence Monitoring Resolution in the Choushui River Fluvial Plain, Taiwan

Precise leveling, global positioning system (GPS), and interferometric synthetic aperture radar (InSAR) have had marked influences on the geodesy field. Many studies have applied these techniques to land subsidence monitoring and predictions. Land subsidence in the Choushui River Fluvial Plain (CRFP) in western central Taiwan is severe, primarily because of excessive groundwater pumping. Exploiting various observational techniques this study employed a geostatistical cokriging algorithm to integrate multiple types of observations for mapping land subsidence in the CRFP between 1993 and 2008 to effectively reduce the regional effects and interpolation biases in InSAR observations. Precise leveling data and persistent scatterer InSAR results were first assessed through variogram analysis, the results of which revealed similar directional variograms and no nugget effect for the experimental variograms. All observed sill values decreased with increasing temporal intervals and the ranges of the same type of observations tended to be stable for time intervals of different lengths. The accuracy of a cokriged land subsidence map was verified using continuous GPS data at the same cell locations and was significantly improved compared to when the precise leveling data were used. The cokriging interpolations of land subsidence in the CRFP indicated that the severe subsidence areas had moved from the coastal area to the central CRFP. An obvious critical subsidence migration point for the southern CRFP occurred in 1998. Overall subsidence rate trends increased in the early periods (1993 - 1998 and 1998 - 2003) and decreased in the most recent period (2005 - 2008).

Temporal patterns of broadcast calls in the corncrake encode information arbitrarily

By combining different vocalizations, in different ways, animals have the potential to vastly increase the range of information that can be encoded in acoustic signals. Although such a mechanism is hard to apply in species having small repertoires, individuals can increase the amount of information by separating vocalizations with intervals of different length, that is, with vocalizations functioning as commas and intervals as carriers of information. Nevertheless, there has been little study of information encoding using temporal arrangement of single call types. We have recently shown that male corncrakes (Crex crex) produce such temporal patterns in correlation to their aggressive motivation and these elicit the according behavior in the receivers. In this study, we report that the design of these patterns is arbitrarily related to their function. The aggressive information is encoded in the syntactic pattern itself, not in the absolute length of intervals, and thus signal variants appear to transfer different kinds of information without any association with the structure of signal variants. The finding of such coding in acoustic signaling in species with innately programmed call structures implies a much larger flexibility and complexity of communication systems of animals in general and in species with low repertoires of genetically coded vocalizations in particular. Key wor ds: coding scheme, conventional communication, corncrake, Cr ex crex, signal function. [Behav Ecol]

Measurement characteristics of finite heart rate plots

We present a comparative analysis of the measurement characteristics of finite real and virtual heart rate plots based on data from 176 serial electrocardiogram recordings, with the aim of comparing data obtained from digital series of R–R intervals of different lengths using the parameters: mean-square value of the standard deviation, quantity of information, and information entropy. We describe a procedure for normalization of the heart rate plots and we explain the role of the excess entropy production parameter.

Dominant speaker identification for multipoint videoconferencing

A multi-point conference is an efficient and cost effective substitute for a face to face meeting. It involves three or more participants placed in separate locations, where each participant employs a single microphone and camera. The routing and processing of the audiovisual information is very demanding on the network. This raises a need for reducing the amount of information that flows through the system. One solution is to identify the dominant speaker and partially discard information originating from non-active participants. We propose a novel method for dominant speaker identification using speech activity information from time intervals of different lengths. The proposed method processes the audio signal of each participant independently and computes speech activity scores for the immediate, medium and long time-intervals. These scores are compared and the dominant speaker is identified. In comparison to other speaker selection methods, experimental results demonstrate reduction in the number of false speaker switches and improved robustness to transient audio interferences.

Momentum trading strategy and investment horizon: an experimental study

PurposeExisting empirical studies that document momentum trading strategies do not provide any insight on how investors choose the time horizon that is used to compute the past stock returns. Indeed, since past returns over overlapping time periods are positively correlated, it is hard to identify the exact historical time period on which investors base their trading strategies and to investigate whether such a period is unique. The purpose of this paper is to investigate this and reach some conclusions.Design/methodology/approachIn this paper the author uses experimental setting to analyze how investors choose which of the past returns to use as a basis for their trading strategies and whether this choice depends on their investment horizon. The advantage of this experimental setting over the existing empirical research is the ability to control for the investment horizon of the subjects and the ability to provide the subjects with a hand‐picked set of stocks with uncorrelated past returns over overlapping time periods. In the study subjects were asked to make short‐term investment decisions based on historical short‐term realized returns over two time intervals of different lengths. In each treatment the subjects were divided into two groups based on the lengths of their investment horizons, which were set to match the lengths of time intervals used to compute the historical returns.FindingsIt was found that subjects followed momentum trading strategies based on both historical returns provided to them and paid more attention to the historical returns over the shorter time period. In addition, some evidence was found that subjects with longer investment horizons rely less on momentum strategies.Originality/valueA wide sample was used to create an original set of observations and conclusions.

Fuzzy Forecasting Based on Fuzzy-Trend Logical Relationship Groups

In this paper, we present a new method to predict the Taiwan Stock Exchange Capitalization Weighted Stock Index (TAIEX) based on fuzzy-trend logical relationship groups (FTLRGs). The proposed method divides fuzzy logical relationships into FTLRGs based on the trend of adjacent fuzzy sets appearing in the antecedents of fuzzy logical relationships. First, we apply an automatic clustering algorithm to cluster the historical data into intervals of different lengths. Then, we define fuzzy sets based on these intervals of different lengths. Then, the historical data are fuzzified into fuzzy sets to derive fuzzy logical relationships. Then, we divide the fuzzy logical relationships into FTLRGs for forecasting the TAIEX. Moreover, we also apply the proposed method to forecast the enrollments and the inventory demand, respectively. The experimental results show that the proposed method gets higher average forecasting accuracy rates than the existing methods.

Forecasting enrollments using automatic clustering techniques and fuzzy logical relationships

In recent years, some researchers focused on the research topic of using fuzzy time series to handle forecasting problems. In this paper, we present a new method to forecast enrollments based on automatic clustering techniques and fuzzy logical relationships. First, we present an automatic clustering algorithm for clustering historical enrollments into intervals of different lengths. Then, each obtained interval will be divided into p sub-intervals, where p ⩾ 1 . Based on the new obtained intervals and fuzzy logical relationships, we present a new method for forecasting the enrollments of the University of Alabama. The proposed method gets a higher average forecasting accuracy rate than the existing methods.

NEST MONITORING DOES NOT INCREASE NEST PREDATION IN OPEN-NESTING SONGBIRDS: INFERENCE FROM CONTINUOUS NEST-SURVIVAL DATA

Abstract The disturbance associated with nest monitoring raises concerns about the validity of the estimated nest success and the well-being of the populations under study. Observer activity may attract or deter predators to or from bird nests, thus decreasing or increasing nest success. Results of previous studies related nest success to frequency of nest visits or estimated survival over rechecking intervals of different length. Such studies usually cannot reveal the underlying mechanism through which predation rate is influenced, because the timing of predation remains unknown. I measured, using data loggers, the exact survival times of 747 nests of 11 songbird species in fragmented woodland in the Czech Republic in 2001–2003 and analyzed the temporal relationship between predation and observer visits. I found only a short-term observer effect that lowered the hazard of predation during 2 h after a visit but did not appreciably affect the overall nest success. The timing of nest visits and the short du...

Cyclicities and clusters in the lacustrine sequence of Heqing basin (SW China): Its use for dating and palaeoenvironmental reconstruction

Himalayan Journal of Sciences Vol.2(4) Special Issue 2004 pp.145

The characterestics of the equally weighted market index and the value weighted market index and their implications for market based accounting research: The case of ase

This study examines empirically the characteristics of the two market indices developed by Amman Stock Exchange (ASE) and their related returns: the equally weighted index (EWI) and the value weighted index (VWI). The monthly‐prices for each index are obtained from ASE for the entire nine‐year period (1992‐2000) to compute market returns for both indices. The study period is divided into seven intervals of different lengths. The results of the test and the nonparametric (Wilcoxon) test indicate that the value weighted market return (VWR) tends to be significantly higher than the equally‐weighted market return (EWR). The variances of the two market returns tend to decrease as the length of the time intervals increases. Inconsistent with prior research findings, the differences between the two market returns variances failed to be significant at the 0.05 level. The study findings may have implications for capital market research that apply the market model in emerging markets, in general, and in ASE in particular.

Possible origin of the non-linear long-term autocorrelations within the Gaussian regime

In this work we extend the recently considered toy model of Weierstrass or Lévy walks with varying velocity of the walker (Quantitative Finance 3 (2003) 201; Chem. Phys. 284 (2002) 481; Comp. Phys. Comm. 147 (2002) 565; Phys. A 264 (1999) 84; Phys. A 264 (1999) 107) by introducing a more realistic possibility that the walk can be occasionally intermitted by its momentary localization; the localizations themselves are again described by the Weierstrass or Lévy process. The direct empirical motivation for developing this combined model is, for example, the dynamics of financial high-frequency time series or hydrological and even meteorological ones where variations of the index are randomly intermitted by flat intervals of different length exhibiting no changes in the activity of the system. This combined Weierstrass walks was developed in the framework of the non-separable generalized continuous-time random walk formalism developed very recently (Lecture Notes Comput. Sci. 2657 (2003) 407; Eur. Phys. J. B 33 (2003) 495). This non-Markovian two-state (walking-localization) model makes possible to cover by the unified treatment a broad band of known up to now types of non-biased diffusion from the dispersive one over the normal, enhanced, ballistic, and hyperdiffusion up to the Richardson law of diffusion which defines here a part of the borderline which separates the latter from the ‘Lévy ocean’ where the total mean-square displacement of the walker diverges. We observed that anomalous diffusion is characterized here by three fractional exponents: one (temporal) characterizing the localized state and two (temporal and spatial) characterizing the walking one. By considering successive dynamic (even) exponents we constructed a series of different diffusion phase diagrams on the plane defined by the temporal and spatial (partial) fractional (dynamic) exponents characterizing the walking state. To adapt the model to the description of empirical data (the discrete time series), which are collected with a discrete time step, we used in the continuous-time series produced by the model a discretization procedure. We observed that such a procedure generates, in general, long-range non-linear autocorrelations even in the Gaussian regime, which appear to be similar to those observed, e.g., in the financial time series (Phys. A 287 (2000) 396; Phys. A 299 (2001) 1; Phys. A 299 (2001) 16; Phys. A 299 (2001) 16), although single steps of the walker within continuous time are, by definition, uncorrelated. This suggests a suprising origin of long-range non-linear autocorrelations alternative to the one proposed very recently (cf. Mosaliver et al. (Phys. Rev. E 67 (2003) 021112) and refs. therein) although both approaches involve related variants of the well-known continuous-time random walk formalism applied yet in many different branches of knowledge (Phys. Rep. 158 (1987) 263; Phys. Rep. 195 (1990) 127; in: A. Bunde, S. Havlin (Eds.), Fractals in Science, Springer, Berlin, 1995, p. 1).

Study of the non-linear autocorrelations within the Gaussian regime

In this work we extend the recently considered toy model of Weierstrass or Levy walks with varying velocity of the walker [1] by introducing a more realistic possibility that the walk can be occasionally intermitted by its momentary localization; the localizations themselves are again described by the Weierstrass or Levy process. The direct empirical motivation for developing this combined model is, for example, the dynamics of financial high-frequency time series or hydrological and even meteorological ones where variations of the index are randomly intermitted by flat intervals of different length exhibiting no changes in the activity of the system. This combined Weierstrass walks was developed in the framework of the non-separable generalized continuous-time random walk (GCTRW) formalism developed recently [2]. This approach makes it possible to study by stochastic simulations the whole spatial-temporal range while analytically we can study only the initial, pre-asymptotic and asymptotic regions (but not the intermediate one). Our approach is possible since the Weierstrass walks is a geometric superposition of regular random walks each of which can be simply treated by stochastic simulations. This non-Markovian two-state (walking-localization) model makes possible to cover by the unified treatment a broad band of known up to now types of non-biased diffusion from the dispersive one over the normal, enhanced, ballistic, and hyperdiffusion up to the Richardson law of diffusion which defines here a part of the borderline which separates the latter from the `Levy ocean' where the total mean-square displacement of the walker diverges. We observed that anomalous diffusion is characterized here by three fractional exponents: temporal one characterizing the localized state and two, temporal and spatial ones, characterizing the walking state. By considering successive dynamic (even) exponents we constructed a series of different diffusion phase diagrams on the plane defined by the spatial and temporal fractional dimensions of the walking state. To adapt the model to the description of empirical data (or discrete time series) which are collected with a discrete time-step we used in the continuous-time series produced by the model a discretization procedure. We observed that such a procedure generates, in general, long-range non-linear autocorrelations even in the Gaussian regime, which appear to be similar to those observed, e.g., in the financial time series [3–6], although single steps of the walker within continuous time are, by definition, uncorrelated. This suggests a surprising explanation alternative to the one proposed very recently (cf. [7] and Refs. therein) although both approaches involve related variants of the well-known CTRW formalism applied yet in many different branches of knowledge [8–10].