scholarly journals Comparison of estimators in one-phase two-stage Poisson sampling in forest inventories

2012 ◽  
Vol 42 (10) ◽  
pp. 1865-1871 ◽  
Author(s):  
Daniel Mandallaz ◽  
Alexander Massey
Keyword(s):  
Small Area ◽  
Two Stage ◽  
Random Sample Size ◽  
Poisson Sampling ◽  
Second Stage ◽  
Forest Inventories ◽  
Unbiased Estimates ◽  
The Mean ◽  
Concentric Circles ◽  
Better Than

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.

A Two-Stage Combination Model for Wind Power Forecasting

2015 ◽  
Vol 737 ◽  
pp. 9-13
Author(s):  
Jun Zhang ◽  
Yuan Hao Wang ◽  
Ying Yi Li ◽  
Feng Guo
Keyword(s):  
Neural Network ◽  
Bp Neural Network ◽  
Wind Farm ◽  
General Trend ◽  
Two Stage ◽  
Combination Model ◽  
Second Stage ◽  
Combination Forecasting ◽  
The Mean ◽  
Power Sequence

With the wind farm data from the southeast coast this paper builds a two-stage combination forecasting model of output power based on data preprocessing which include filling up missing data and pre-decomposition. The first stage is a composite prediction of decomposed power sequence in which a time series and optimized BP neural network predict the general trend and the correlation of various factors respectively. The second stage is BP neural network with its input is the results of first stage. The effectiveness and accuracy of the two-stage combination model are verified by comparing the mean square error of the combination model and other models.

scholarly journals Evidence for a two-stage model of microbial infection

1968 ◽  
Vol 66 (2) ◽  
pp. 273-280 ◽  
Author(s):  
G. G. Meynell ◽  
Joan Maw
Keyword(s):  
Standard Error ◽  
Stage Model ◽  
Microbial Infection ◽  
Two Stage ◽  
Second Stage ◽  
Initial Stage ◽  
The Mean ◽  
Pass Through

SUMMARYColony counts on mice given the same number ofSalmonellaalways differ considerably. However, the standard error of the mean log count does not increase after the first 1·5 hr. of infection until the 8th or 10th day. These infections therefore appear to pass through an initial stage lasting a few hours, in which a varying proportion of the inoculum is killed, followed by a prolonged second stage in which the scatter in individual colony counts remains constant.

scholarly journals Design and Analysis of a Split Deswirl Vane in a Two-Stage Refrigeration Centrifugal Compressor

2014 ◽  
Vol 6 ◽  
pp. 130925 ◽  
Author(s):  
Jeng-Min Huang ◽  
Yue-Hann Tsai
Keyword(s):  
Centrifugal Compressor ◽  
Rotation Angle ◽  
Guide Vane ◽  
Low Flow ◽  
Working Fluid ◽  
Inlet Guide Vane ◽  
Two Stage ◽  
Double Row ◽  
Second Stage ◽  
Better Than

This study numerically investigated the influence of using the second row of a double-row deswirl vane as the inlet guide vane of the second stage on the performance of the first stage in a two-stage refrigeration centrifugal compressor. The working fluid was R134a, and the turbulence model was the Spalart-Allmaras model. The parameters discussed included the cutting position of the deswirl vane, the staggered angle of two rows of vane, and the rotation angle of the second row. The results showed that the performance of staggered angle 7.5° was better than that of 15° or 22.5°. When the staggered angle was 7.5°, the performance of cutting at 1/3 and 1/2 of the original deswirl vane length was slightly different from that of the original vane but obviously better than that of cutting at 2/3. When the staggered angle was 15°, the cutting position influenced the performance slightly. At a low flow rate prone to surge, when the second row at a staggered angle 7.5° cutting at the half of vane rotated 10°, the efficiency was reduced by only about 0.6%, and 10% of the swirl remained as the preswirl of the second stage, which is generally better than other designs.

scholarly journals One-Stage Multiple Comparisons with the Control for Exponential Median Lifetimes under Heteroscedasticity

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1405 ◽  
Author(s):  
Shu-Fei Wu
Keyword(s):  
Lung Cancer ◽  
Chemotherapeutic Agent ◽  
Multiple Comparisons ◽  
Central Tendency ◽  
Second Stage ◽  
One Stage ◽  
Pharmaceutical Industries ◽  
The Mean ◽  
Additional Sample ◽  
Better Than

When the additional sample for the second stage may not be available, one-stage multiple comparisons for exponential median lifetimes with the control under heteroscedasticity including one-sided and two-sided confidence intervals are proposed in this paper since the median is a more robust measure of central tendency compared to the mean. These intervals can be used to identify treatment populations that are better than the control or worse than the control in terms of median lifetimes in agriculture, stock market, pharmaceutical industries. Tables of critical values are obtained for practical use. An example of comparing the survival days for four categories of lung cancer in a standard chemotherapeutic agent is given to demonstrate the proposed procedures.

scholarly journals Two-stage sector sampling for estimating small woodlot attributes

2011 ◽  
Vol 41 (9) ◽  
pp. 1819-1826 ◽  
Author(s):  
Piermaria Corona ◽  
Lorenzo Fattorini ◽  
Sara Franceschi
Keyword(s):  
Large Scale ◽  
Sampling Strategy ◽  
Sampling Variance ◽  
Sampling Strategies ◽  
Fixed Size ◽  
Two Stage ◽  
Sampling Schemes ◽  
Second Stage ◽  
Forest Inventories ◽  
Plot Sampling

A two-stage sampling strategy is proposed to assess small woodlots outside the forests scattered on extensive territories. The first stage is performed to select a sample of small woodlots using fixed-size sampling schemes, and the second stage is performed to sample trees within woodlots selected at first stage. Usually, fixed- or variable-area plots are adopted to sample trees. However, the use of plot sampling in small patches such as woodlots is likely to induce a relevant amount of bias owing to edge effects. In this framework, sector sampling proves to be particularly effective. The present paper investigates the statistical properties of two-stage sampling strategies for estimating forest attributes of woodlot populations when sector sampling is adopted at the second stage. A two-stage estimator of population totals is derived together with a conservative estimator of its sampling variance. By means of a simulation study, the performance of the proposed estimator is checked and compared with that achieved using traditional plot sampling with edge corrections. Simulation results prove the adequacy of sector sampling and provide some guidelines for the effective planning of the strategy. In some countries, the proposed strategy can be performed with few modifications within the framework of large-scale forest inventories.

Wastewater Minimisation Using a Heuristic Procedure

2004 ◽  
Vol 2 (1) ◽  
Author(s):  
Zhi-Yong Liu ◽  
Zisheng Jason Zhang ◽  
Linna Hu ◽  
Zhaoliang Wu
Keyword(s):  
Mass Balance ◽  
Heuristic Procedure ◽  
Heuristic Rules ◽  
Two Stage ◽  
Flow Rates ◽  
Second Stage ◽  
Better Than

A two-stage procedure is proposed for the minimisation of wastewater. In the first stage, heuristic rules are used to find the initial feasible flowsheet; in the second stage, the flow rates of streams in the initial flowsheet are determined by mass balance of the contaminants. The operations considered in this work include re-use, regeneration, mixing and bypassing of water streams. The proposed procedure is simple and the results of the examples studied are comparable with or better than those found in the literature.

scholarly journals Effect of C/N Ratio on the Removal of Nitrogen and Microbial Characteristics in the Water Saturated Denitrifying Section of a Two-Stage Constructed Rapid Infiltration System

2018 ◽  
Vol 15 (7) ◽  
pp. 1469 ◽  
Author(s):  
Qinglin Fang ◽  
Wenlai Xu ◽  
Gonghan Xia ◽  
Zhicheng Pan
Keyword(s):  
Extracellular Polymeric Substances ◽  
Oxygen Demand ◽  
Denitrifying Bacteria ◽  
Major Constituent ◽  
Two Stage ◽  
Second Stage ◽  
Microbial Characteristics ◽  
The Mean ◽  
Water Saturated ◽  
Nitrogen Pollutants

The aim of this study was to improve the removal of nitrogen pollutants from artificial sewage by a modeled two-stage constructed rapid infiltration (CRI) system. The C/N ratio of the second stage influent was elevated by addition of glucose. When the C/N ratio was increased to 5, the mean removal efficiency of total nitrogen (TN) reached up to 75.4%. Under this condition, the number of denitrifying bacteria in the permanently submerged denitrifying section (the second stage) was 22 times higher than that in the control experiment without added glucose. Elevation of the C/N ratio resulted in lower concentrations of nitrate and TN in the second stage effluent, without impairment of chemical oxygen demand removal. The concentration of nitrate and TN in effluent decreased as the abundance of denitrifying bacteria increased. Moreover, the bacterial biofilms that had formed in the sand of the second stage container were analyzed. The secretion of extracellular polymeric substances, a major constituent of biofilms, was enhanced as a result of the elevated C/N ratio, which lead to the improved protection of the bacteria and enhanced the removal of pollutants.

Treatment of Leachate by Aged-Refuse Reactor in Natural Ventilation during Autumn and Winter

2011 ◽  
Vol 374-377 ◽  
pp. 821-825
Author(s):  
Jie Yu Luo ◽  
Xiao Jie Sun ◽  
Dun Qiu Wang ◽  
Yi Nian Zhu
Keyword(s):  
Natural Ventilation ◽  
Removal Rate ◽  
Effect Of Temperature ◽  
Two Stage ◽  
Second Stage ◽  
Treated Effluent ◽  
Aged Refuse ◽  
Cod Removal Rate ◽  
Autumn And Winter ◽  
Better Than

The effect of temperature on two stage aged-refuse-based reactor which treats leachate in natural ventilation was investigated in autumn and winter. Results indicate that the average concentrations of COD in treated effluent increase from 726 mg/L in autumn to 2000 mg/L in winter in the first stage reactor while they are 246 mg/L and 1010 mg/L respectively in the second stage reactor. The average concentrations of NH3-N in treated effluent increase from 123.7 mg/L in autumn to 620 mg/L in winter in the first stage reactor while they are 123.7 mg/L and 620 mg/L respectively in the second stage reactor. Accordingly, the average removal rates of COD decrease from 81.7% of autumn to 73% of winter in the first stage reactor and decrease from 64.7% to 52% in the second stage reactor, and finally, the total COD removal rate in this system drops from 92.7% in autumn to 85.8% in winter. So we can conclude that the effect of temperature on the first stage aged refuse reactor is better than that on the second stage aged refuse reactor.

scholarly journals Inequitable wages and tax evasion

2020 ◽  
Author(s):  
Linda Dezső ◽  
James Alm ◽  
Erich Kirchler
Keyword(s):  
Tax Evasion ◽  
Tax Compliance ◽  
Lab Experiment ◽  
Two Stage ◽  
Second Stage ◽  
Human Choice ◽  
Income Ratio ◽  
Group Members ◽  
The Mean ◽  
Per Se

In a two-stage, preregistered lab experiment (aspredcited.com #36099), weexamine whether wage inequity has a greater impact on tax compliance and onthe beliefs about prevailing compliance norms among the wronged when it results from intentional human choice versus a random mechanism. Subjects areorganized into groups of six. In the ?the first stage, we perform a wage inequity manipulation by assigning equitable or inequitable wages to subjects as remuneration for a trivial, real-e?ort task. In the second stage, subjects are prompted to report their incomes, of which a certain percent is deducted but not redistributedbetween them. Next, subjects state their incentivized beliefs about the mean ofthe declared-to-true income ratio among their group members. We ?nd that taxcompliance and beliefs about the prevailing compliance norms are eroded whenwage inequity stems from intentional human choice but not when the same wageis randomly chosen. Consequently, it is not the wage inequity per se that reducestax compliance and corrupts beliefs about the norms, but rather the inequity dueto human choice. Our results demonstrate that incidental unfairness in the formof intentional wage inequity adversely spills over onto tax compliance and beliefsabout the prevailing compliance norms. In conclusion, intentional wage inequitycan be harmful for the society as a whole.

scholarly journals Tips and Tricks in surgical reduction of the posterior column of AO/OTA C3 pilon fractures

2022 ◽  
Vol 23 (1) ◽  
Author(s):  
Moran Huang ◽  
Qiuke Wang ◽  
Junjie Guan ◽  
Kexin Liu ◽  
Yunfeng Chen ◽  
...  
Keyword(s):  
Posterior Column ◽  
Posterolateral Approach ◽  
Foot And Ankle ◽  
Two Stage ◽  
Aofas Score ◽  
Second Stage ◽  
Controversial Topic ◽  
The Mean ◽  
Ankle Function ◽  
Pilon Fractures

Abstract Background Accurate posterior column reduction remains a challenging and controversial topic in the management of complex pilon fractures (AO/OTA C3). We aim to report the outcomes of surgical treatment for 22 AO/OTA C3 pilon fracture cases between January 2015 and May 2017 and highlight some traps and tips. Methods Three patients underwent two-stage early plating on the posterior column through a posterolateral approach. The remaining 19 patients were treated with two-stage delayed plating on the posterior column: 11 patients were treated with a posterolateral approach, five patients with a modified posteromedial approach, and three patients with a single anterior approach. The reduction of the posterior column was evaluated according to the Burwell-Charnley’s radiographic criteria, and functional outcomes were assessed using the American Orthopedic Foot and Ankle Society (AOFAS) scores. Results Posterior column malreduction occurred in five cases, including in one case that was re-adjusted immediately and in another case that was re-adjusted during a two-staged delayed operation. According to Burwell-Charnley’s criteria, the satisfactory rate of fracture reduction was 81.8%. After 1 year, the mean AOFAS score was 81.9 (81.9 ± 9.9); the outcome was excellent in three (20.0%), good in nine (60.0%), and fair in three (20.0%). Excellent or good outcomes were noted in 12 patients (80.0%). Conclusions The combined anterior and posterior approach is suggested in the second stage of plating so that the posterior column fragments can be re-adjusted intraoperatively, if necessary. Following these procedures, satisfactory reduction and recovery of good ankle function can be anticipated.

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