Percentile Method Research Articles

Application of quantile methods to estimation of Cauchy distribution parameters

Quantile methods are used for estimation of population parameters when other methods such as the maximum likelihood method and the method of moments cannot be applied. In the paper the percentile method, the quantile least squares method and its two modifications are considered. The proposed methods allow estimators to be obtained with smaller bias and smaller mean squared error than estimators of the quantile least squares method. The considered methods can be applied to estimation of the Cauchy distribution parameters. The results of the simulation analysis of the estimator properties have allowed conclusions to be drawn as concerning the application of the considered methods.

미계측 유역에서 저수량 산정 방법 비교 연구

In this study, the methodologies for evaluating the low-flow at the ungauged watershed are reviewed and assessed. The ungauged watershed can be classified into different situations such as the partially recorded watershed and the completely ungauged watershed. The extension method and the percentile method are used to evaluated the low-flow at the partially recorded watershed. The drainage-area ratio method and the regional regression method are used at the completely ungauged watershed. These four methods are applied and validated based on the hydrological and geometric data acquired from unit watersheds in Han River basin for TMDLs. In case of partially recorded watershed, the values of low-flow evaluated by the extension method are in better agreement with measured flow-rate rather than those by the percentile method. In case of completely ungauged watershed, the drainage-area method is broadly used to estimate the low-flow. It must be paid attention to consider the treated sewage discharge produced at watersheds when applying the method.

An empirical study of the impact of lean construction techniques on sustainable construction in the UK

Purpose– The contribution of lean construction techniques in sustainable construction cannot be over emphasised, as sustainable development is now enshrined in government policy. In addition, lean construction is now faced with the challenges of sustainable development, continuous improvement, waste elimination, a stronger user focus, increased value for money along with high quality management of projects and supply chains, and improved communications. This paper presents an exploratory study from extant literature and the results of the use of questionnaire survey among construction participants to explore the contribution of implementing lean construction techniques in sustainable construction.Design/methodology/approach– Surveys of UK-based construction professional were conducted. The data collected were analysed with SPSS 19.0 version software using the percentile method, Cronbach ' sαreliability test, Kruskal Wallis test, Kendall ' s coefficient of concordance and one samplet-test.Findings– Results from this study indicate that there are several benefits associated with implementation of lean construction and sustainable construction. The overall perspective of professionals within the construction industry, according to questionnaire survey, shows that benefits such as improved corporate image and sustainable competitive advantage, improved process flow and productivity, improvement in environmental quality and increased compliance with customer ' s expectations are realised following integration of principles of lean construction and sustainable construction within construction industry. Just-in-time, visualisation tool, value analysis, daily huddle meetings and value stream mapping are the most common lean tools/techniques for enabling sustainability. This study also identified several areas of linkage between lean and sustainability such as waste reduction, environmental management, value maximisation, and health and safety improvement among others.Originality/value– The originality of this paper lies in its consideration of lean construction principles to better understand its impact on sustainable construction. This research contributes to the awareness of the benefits that can be derived from the implementation of lean construction in sustainable construction within the construction industry.

Development of empirical standard weight equation for Pursak chub Squalius pursakensis, an endemic cyprinid species of Northwest Anatolia

Indices of condition enable the evaluation of the well-being of fish, with the assumption that heavier fish of a given length are in a better condition. Relative weight (Wr) is one of these indices; it is calculated by comparing the actual weight of a specimen with the ideal weight of a specimen in good physiological condition of the same length from the same species, i.e. standard weight (Ws). In this research, length and weight data over the distribution range for Pursak chub Squalius pursakensis, an endemic species distributed in the Sakarya and Porsuk drainages in Northwest Anatolia (Turkey), were used to compute a Ws equation by means of the empirical percentile (EmP) method. The Ws equation obtained was log10 Ws = -4.657 + 2.614 log10 TL + 0.127 (log10 TL)2, and the total length range of application was 80-340 mm. Since the EmP Ws equation was not influenced by length variation, the use of this equation to compute the relative weight (Wr) for S. pursakensis throughout its area of distribution is suggested.

Development of empirical standard weight equation for Pursak chub Squalius pursakensis, an endemic cyprinid species of Northwest Anatolia

Indices of condition enable the evaluation of the well-being of fish, with the assumption that heavier fish of a given length are in a better condition. Relative weight (W_{r}) is one of these indices; it is calculated by comparing the actual weight of a specimen with the ideal weight of a specimen in good physiological condition of the same length from the same species, i.e. standard weight (W_{s}). In this research, length and weight data over the distribution range for Pursak chub Squalius pursakensis, an endemic species distributed in the Sakarya and Porsuk drainages in Northwest Anatolia (Turkey), were used to compute a W_s equation by means of the empirical percentile (EmP) method. The W_s equation obtained was log_{10} W_s = -4.657 + 2.614 log_{10} TL + 0.127 (log_{10} TL)^{2}, and the total length range of application was 80-340 mm. Since the EmP W_s equation was not influenced by length variation, the use of this equation to compute the relative weight (W_r) for S. pursakensis throughout its area of distribution is suggested.

Probabilistic Approach for Evaluating the Capacity Value of Intermittent Generation

SUMMARY Several approaches have been proposed for evaluating the capacity value of intermittent generation. In this paper, we assume that the uncertainty included in demand, existing generation, and intermittent generation, can be treated by means of a normal distribution model. Using a newly developed approximation method similar to the Garver approximation, and the Z-stochastic approach, the effective load carrying capability method is comprehensively surveyed. The percentile method adopted in the higher demand level is also discussed in connection with the probabilistic properties of intermittent generation. Numerical examples and a simulation illustrating the probabilistic approach are included.

Analysis and Extension of the Percentile Method, Estimating a Noise Curve from a Single Image

Given a white Gaussian noise signal on a sampling grid, its variance can be estimated from a small block sample. However, in natural images we observe the combination of the geometry of the scene being photographed and the added noise. In this case, estimating directly the standard deviation of the noise from block samples is not reliable since the measured standard deviation is not explained just by the noise but also by the geometry of the image. The Percentile method tries to estimate the standard deviation of the noise from blocks of a high-passed version of the image and a small p-percentile of these standard deviations. The idea behind is that edges and textures in a block of the image increase the observed standard deviation but they never make it decrease. Therefore, a small percentile (0.5%, for example) in the list of standard deviations of the blocks is less likely to be affected by the edges and textures than a higher percentile (50%, for example). The 0.5%-percentile is empirically proven to be adequate for most natural, medical and microscopy images. The Percentile method is adapted to signal-dependent noise, which is realistic with the Poisson noise model obtained by a CCD device in a digital camera.

Subjective symptoms related to GSM radiation from mobile phone base stations: a cross-sectional study

ObjectivesWe performed a re-analysis of the data from Navarro et al (2003) in which health symptoms related to microwave exposure from mobile phone base stations (BSs) were explored, including data...

Frequency analysis of precipitation extremes in Heihe River basin based on generalized Pareto distribution

Precipitation extremes could cause a series of social, environmental and ecological problems. This paper, taking Heihe River basin, the second largest inland river basin in China, as the study area, focused on the frequency analysis of precipitation extremes based on the historical daily precipitation records (1960–2010) at nine stations. Generalized Pareto distribution (GPD) was employed for fitting the peaks over threshold (POT) series, in which Hill plot, percentile method and the average annual occurrence number were used to select the threshold in GPD. Maximum likelihood estimate and L-moment were used to estimate the parameters. The inherent assumptions for POT series were investigated by auto-correlation coefficient, Mann–Kendall test, Spearman’s ρ test, cumulative deviation test and Worsley likelihood ratio test. 10, 20, 50 and 100 year precipitation extremes for Heihe River basin were calculated and analyzed as well. It was found the POT series derived from several methods involved were approximately independent and stationary, and GPD could give a satisfactory fit to the POT series for each station. For the upper and lower reaches, the frequency of precipitation extremes at long return periods (20, 50 year or longer) presented increasing in recent years, and the intensity of the highest precipitation were getting stronger as well. The intensity of the highest precipitation extremes for the lower reach (21 and 35 %) increased higher than those for the upper reach (10 and 11 %). For the middle reach, the frequency of precipitation extremes (over 20 year return level) was not found to be increased. The uneven spatial and temporal distribution of precipitation extremes for the basin especially for the upper and lower reaches were getting more and more serious, which would bring great challenges for the local water allocation and management.

Assessing floating treatment wetlands nutrient removal performance through a first order kinetics model and statistical inference

A floating treatment wetland (FTW) is an ecological approach which seeks to reduce point and nonpoint source pollution in receiving waters. This technology has received increasing attention recently. Subsequent studies were conducted at worldwide locations; despite these efforts, reliable estimates of the FTW performance remains a significant research gap. This paper describes the development of a robust and simplified integrated FTW (i-FTW) model that includes uncertainty. The performance of FTWs was separated from other treatment processes ongoing within their respective water bodies. This approach facilitates generalization of the model and allowing parameters to adjust to each applied water body characteristic. A bootstrap method was incorporated to estimate uncertainty and generate more robust predictions of performance.Water concentration time series data were described by a first order kinetics i-FTW model that generates an FTW performance parameter: FTW apparent uptake velocity (vf). A comprehensive literature search of i-FTW studies was conducted to collect total phosphorus (TP) and total nitrogen (TN) concentrations data. The vf values were calculated from these studies and estimated using a bootstrap percentile method. The best estimation of median and expected range with 95% confidence interval of the vf were 0.048 (0.018–0.059) and 0.027 (0.016–0.040)m/day for TP and TN, respectively. The goodness of fit (R2) of the i-FTW model on water concentration time series data of the i-FTW experiments was 0.92±0.30 for TP and 0.86±0.38 for TN data (mean±SD). This model provides insights into compartmental treatments of i-FTW systems and serves as a preliminary tool to select extent of FTW coverage when designing an i-FTW system. Further research to resolve limitations of model application is suggested.

The Dimensionality of Contextual and Citizenship Performance in Military Recruits: Support for Nine Dimensions Using Self-, Peer, and Supervisor Ratings

Organizational Citizenship Behavior and Contextual Performance make up a domain that can be referred to as Contextual and Citizenship Performance (CCP). CCP is essential to assess and promote in military and civilian organizations because it defines the “good soldier” prototype. Unfortunately, extant research has led to confusion as to whether CCP consists of one, two, three, six, or nine dimensions. We shed new light on the composition of CCP by evaluating one-, two-, three-, six-, and nine-dimensional theoretical models using supervisor, self-, and peer ratings of military recruits undergoing basic training. We employed Relative Percentile Method ratings to improve distinctions among ratees when the level of CCP is high. Contrary to much recent literature, our results supported a nine-dimensional theoretical model in all three rating sources. Thus, conceptualizing, assessing and promoting the proverbial “good soldier” may require a more highly nuanced perspective of CCP than is generally acknowledged.

Performance evaluation of CIDARS on dengue fever outbreak detection, China

Performance evaluation of CIDARS on dengue fever outbreak detection, China Honglong Zhanga#, Zhongjie Lia#, Shengjie Laia, Archie Clementsb, Wenbiao Hub*, Weizhong Yanga* a Key Laboratory of Surveillance and Early-warning on infectious Disease, Division of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing 102206 b School of Population Health, The University of Queensland, Brisbane 4006 QLD, Australia #: These authors contributed equally *Correspondence? Weizhong Yang: yangwz@chinacdc.cn Wenbiao Hu: w.hu@sph.uq.edu.au Background For more effective prevention and control of dengue fever (DF), a China Infectious Disease Automated-alert and Response System (CIDARS) was used to identify possible early warning signals of DF outbreaks at country level in China. Aims This study aims to evaluate the performance of the CIDARS early warning system for DF. Methods In CIDARS a time series moving percentile method was used to detect the outbreak of DF. If the cases of reported DF are over 50 percentile of historical data, an early warning signal will be generated and sent to the local county CDC staff who are responsible for certifying and investigating the signals. In this study, descriptive analysis was used to display the spatial and temporal patterns of DF reported cases and early warning signals of DF during the study period. Sensitivity, specificity and timeliness were employed to assess the performance of DF early warning in CIDARS. Results There were 651 reported DF cases in China between 1st January 2009 and 31st December 2011. 58 signals were mostly occurred between August and December and distributed in Guangdong (35), Zhejiang (7) and Guangxi (4) provinces. 93.10% signals were responded within 24 hours. There were 9 outbreaks of DF recorded during study period with 8 (88.9%) outbreaks detected by CIDARS. The average time of outbreaks detection by CIDARS was 0.63 day. Conclusions CIDARS is a useful platform to detect the DF outbreak at early stage. More accurate algorithms could be tested to reduce the negative signals.

Performance evaluation of CIDARS on dengue fever outbreak detection, China

Performance evaluation of CIDARS on dengue fever outbreak detection, China HongLong Zhanga#, Zhongjie Lia#, Shengjie Laia, Archie Clementsb, Wenbiao Hub*, Weizhong Yanga* a Key Laboratory of Surveillance and Early-warning on infectious Disease, Division of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing 102206 b School of Population Health, The University of Queensland, Brisbane 4006 QLD, Australia #: These authors contributed equally *Correspondence? Weizhong Yang: yangwz@chinacdc.cn Wenbiao Hu: w.hu@sph.uq.edu.au Background For more effective prevention and control of dengue fever (DF), a China Infectious Disease Automated-alert and Response System (CIDARS) was used to identify possible early warning signals of DF outbreaks at country level in China. Aims This study aims to evaluate the performance of the CIDARS early warning system for DF. Methods In CIDARS a time series moving percentile method was used to detect the outbreak of DF. If the cases of reported DF are over 50 percentile of historical data, an early warning signal will be generated and sent to the local county CDC staff who are responsible for certifying and investigating the signals. In this study, descriptive analysis was used to display the spatial and temporal patterns of DF reported cases and early warning signals of DF during the study period. Sensitivity, specificity and timeliness were employed to assess the performance of DF early warning in CIDARS.Results There were 651 reported DF cases in China between 1st January 2009 and 31st December 2011. 58 signals were mostly occurred between August and December and distributed in Guangdong (35), Zhejiang (7) and Guangxi (4) provinces. 93.10% signals were responded within 24 hours. There were 9 outbreaks of DF recorded during study period with 8 (88.9%) outbreaks detected by CIDARS. The average time of outbreaks detection by CIDARS was 0.63 day. Conclusions CIDARS is a useful platform to detect the DF outbreak at early stage. More accurate algorithms could be tested to reduce the negative signals.

Uncertainty in determining extreme precipitation thresholds

Summary Extreme precipitation events are rare and occur mostly on a relatively small and local scale, which makes it difficult to set the thresholds for extreme precipitations in a large basin. Based on the long term daily precipitation data from 62 observation stations in the Pearl River Basin, this study has assessed the applicability of the non-parametric, parametric, and the detrended fluctuation analysis (DFA) methods in determining extreme precipitation threshold (EPT) and the certainty to EPTs from each method. Analyses from this study show the non-parametric absolute critical value method is easy to use, but unable to reflect the difference of spatial rainfall distribution. The non-parametric percentile method can account for the spatial distribution feature of precipitation, but the problem with this method is that the threshold value is sensitive to the size of rainfall data series and is subjected to the selection of a percentile thus make it difficult to determine reasonable threshold values for a large basin. The parametric method can provide the most apt description of extreme precipitations by fitting extreme precipitation distributions with probability distribution functions; however, selections of probability distribution functions, the goodness-of-fit tests, and the size of the rainfall data series can greatly affect the fitting accuracy. In contrast to the non-parametric and the parametric methods which are unable to provide information for EPTs with certainty, the DFA method although involving complicated computational processes has proven to be the most appropriate method that is able to provide a unique set of EPTs for a large basin with uneven spatio-temporal precipitation distribution. The consistency between the spatial distribution of DFA-based thresholds with the annual average precipitation, the coefficient of variation (CV), and the coefficient of skewness (CS) for the daily precipitation further proves that EPTs determined by the DFA method are more reasonable and applicable for the Pearl River Basin.

Head circumference: The forgotten tool for hydrocephalus management. A reference interval study in the Spanish population

IntroductionIn children, deviations from the normal range of head circumference (HC) have traditionally been related with CSF dynamics abnormalities. In adults, this neglected parameter is helpful in the diagnosis and understanding of the pathophysiology of some CSF abnormalities. It has been demonstrated that HC is related to height. Because humans have increased in stature dramatically during the last 50 years, pediatric charts for head growth physiology and normal HC values in adults should be reevaluated. ObjectivesThe main aim of the present study was to assess HC in a series of 270 normal healthy Spanish adults and to determine any differences between sexes and age groups. A secondary aim was to discuss the relevance of this parameter in the management of hydrocephalus in adult people. MethodsHC measurements were taken using a measuring tape placed over the greatest frontal and occipital protuberances. The reference interval and the upper and lower thresholds for HC were calculated by 3 different methods: normal distribution, the non-parametrical percentile method, and the “robust method”. ResultsThe results were consistent and showed that Spanish adult men with a HC greater than 60cm, and Spanish adult women with a HC greater than 58cm should be considered macrocephalic. Microcephaly should be considered when HC is 53.6cm in men and 51.3cm in women. Adult age groups of either sex do not present any statistically significant differences in HC. ConclusionsHC obtained in Spanish adult people are greater than those reported in the classical Nellhaus graphs in both men and women aged 18. These findings should be considered in the management of hydrocephalus in adults today.

Comparison of Four Bootstrap-Based Interval Estimators of Species Occupancy and Detection Probabilities

Summary: Site occupancy, as estimated by the probability of presence, is used for monitoring species populations. However, the detection of species at individual sites is often subject to errors. In order to accurately estimate occupancy we must simultaneously account for imperfect detectability by estimating the probability of detection. The problem with estimating occupancy arises from not knowing whether a nondetection occurred at an occupied site due to imperfect detectability (sampling zeros), or the nondetection resulting from an unoccupied site (fixed zeros). We evaluated the performance of the basic, normal approximation, studentised and percentile methods for approximating confidence limits for occupancy and detection of species. Using coverage and average interval width, we demonstrated that the studentised estimator was generally superior to the others, except when a small sample of sites are selected. Under this circumstance and when calculating limits for detection, no estimator produced reliable results. The experimental factors we considered include: (i) number of sites; (ii) number of survey occasions; (iii) probabilities of presence (occupancy) and detection; and (iv) overdispersion in the capture matrix. Similar conclusions were reached both for the simulated studies and a case study. Overall, estimation near the boundaries of the probability of occupancy and detectability was difficult. © 2013 Australian Statistical Publishing Association Inc. Published by Wiley Publishing Asia Pty Ltd.

Ultrasonographic dimensions of the common bile duct in Chinese children: Results of 343 cases

BackgroundAt present, the diagnostic criteria of congenital cholangiectasis are still vague. PurposeThe aim of this study was to assess the diameter references of the common bile duct (CBD) in pediatric population in different age groups with ultrasound. MethodsThe diameter of the common bile duct was measured with ultrasound in 343 Chinese Han children aged 1day to 14years (mean: 3.2years, median: 2.8years) who were all free of hepatic and biliary tract disease. The ultrasound records, gender, and age were collected for reviewed analysis. ResultsA total of 343 children were included, and the CBD was clearly detected in 322 cases (93.9%). The mean diameter of this population was 1.58±0.70mm. (ranging from 0.4 to 4.4mm). Spearman correlation analysis showed that the diameter of CBD was positively associated with age (r=0.573, P<0.001). The percentile method demonstrated that the diameter references of CBD was as follows: ≤1years: ≤2.26mm; ≤4years: ≤2.99mm; ≤7years: ≤3.03mm; and ≤14years: ≤4.10mm. ConclusionsThere was a close correlation between CBD width and the age. The range of CBD widths in each age group will be helpful in the diagnosis of biliary dilatation in childhood.

Economic analysis of coronary artery bypass grafting with minimal versus conventional extracorporeal circulation

Background This study aims to develop a methodological framework for the comparative economic evaluation between Minimal Extracorporeal Circulation (MECC) versus conventional Extracorporeal Circulation (CECC) in patients undergoing coronary artery bypass grafting (CABG) in different healthcare systems. In addition, the scope is to evaluate the cost-effectiveness ratio of alternative comparators in the healthcare setting of Greece, Germany, the Netherlands and Switzerland. Methods The effectiveness data utilized were derived from a recent meta-analysis which incorporated 24 randomized clinical trials. Total therapy cost per patient reflects all resources expensed in delivery of therapy and the management of any adverse events, including drugs, diagnostics tests, materials, devices, blood units, the utilization of operating theaters, intensive care units and wards. Perioperative mortality was used as the primary health outcome to estimate life years gained in treatment arms. Bias-corrected uncertainty intervals were calculated using the percentile method of non-parametric Monte-Carlo simulation. Results The MECC circuit was more expensive than CECC, with a difference ranging from €180 to €600 depending on the country. However, in terms of total therapy cost per patient the comparison favoured MECC in all countries. Specifically it was associated with a reduction of €789 in Greece, €511 in Germany, €2,343 in the Netherlands and €1,141 in Switzerland. In terms of effectiveness, the total life-years gained were slightly higher in favor of MECC. Conclusions Surgery with MECC may be dominant (lower cost and higher effectiveness) compared to CECC in coronary revascularization procedures and therefore it represents an attractive new option relative to conventional extracorporeal circulation for CABG.

Extreme precipitation events identified using detrended fluctuation analysis (DFA) in Anhui, China

Extreme weather events include unusual, severe or unseasonal weather, and weather at the extremes of the historical distribution. They have become more frequent and intense under global warming, especially in mid-latitude areas. They bring about great agricultural and economic losses. It is important to define the threshold of extreme weather event because it is the starting point of extreme weather event research, though it has been of seldom concern. Taking extreme precipitation events in Anhui, China as an example, the detrended fluctuation analysis (DFA) method is introduced to define the threshold of extreme weather events. Based on it, the spatial and temporal distributions of extreme precipitation events are analyzed. Compared to the traditional percentile method, DFA is based on the long-term correlation of time series. Thresholds calculated by DFA are much higher than the 99th percentile and the values are higher in the south and lower in the north. This spatial pattern is similar to the annual precipitation spatial pattern. There is an obvious increasing trend in the number of days with extreme precipitation, especially after the 1980s. This observation supports the point that more extreme events happen under global warming.

Coronary artery bypass grafting with minimal versus conventional extracorporeal circulation; an economic analysis

BackgroundThis study aims to develop a methodological framework for the comparative economic evaluation between Minimal Extracorporeal Circulation (MECC) versus conventional Extracorporeal Circulation (CECC) in patients undergoing coronary artery bypass grafting (CABG) in different healthcare systems. Moreover, we evaluate the cost-effectiveness ratio of alternative comparators in the healthcare setting of Greece, Germany, the Netherlands and Switzerland. MethodsThe effectiveness data utilized were derived from a recent meta-analysis which incorporated 24 randomized clinical trials. Total therapy cost per patient reflects all resources expensed in delivery of therapy and the management of any adverse events, including drugs, diagnostics tests, materials, devices, blood units, the utilization of operating theaters, intensive care units, and wards. Perioperative mortality was used as the primary health outcome to estimate life years gained in treatment arms. Bias-corrected uncertainty intervals were calculated using the percentile method of non-parametric Monte-Carlo simulation. ResultsThe MECC circuit was more expensive than CECC, with a difference ranging from €180 to €600 depending on the country. However, in terms of total therapy cost per patient the comparison favored MECC in all countries. Specifically it was associated with a reduction of €635 in Greece, €297 in Germany, €1590 in the Netherlands and €375 in Switzerland. In terms of effectiveness, the total life-years gained were slightly higher in favor of MECC. ConclusionsSurgery with MECC may be dominant (lower cost and higher effectiveness) compared to CECC in coronary revascularization procedures and therefore it represents an attractive new option relative to conventional extracorporeal circulation for CABG.