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Novel Approach in sampling and Tensile Strength Evaluation of Roots to Enhance Soil for Preventing Erosion

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Open Journal of Soil Science 2018年第12期8卷 330-349页

作者： Shaurav Alam Ashlesh Banjara Jay Wang William B. Patterson Sujan Baral Program of Civil Engineering Louisiana Tech University Ruston LA USA School of Agricultural Sciences and Forestry Louisiana Tech University Ruston LA USA

This paper presents novel approaches to address the complex issues associated with preservation, transportation, and tensile testing of the vegetation root samples needed for the enhancement of soil and prevent erosion. Readily availability of no equipment for in-situ assessment of the roots’ contribution to soil strength forces the researchers to transport the root samples to the lab for testing and estimating the contribution to the soil shear strength. Moreover, the standard procedures and apparatuses available in the public domain are regrettably suitable for testing of relatively stiffer materials. Therefore, conducting the tensile test of roots using off-the-shelf equipment often causes premature failure of the soft tissues and produces an erratic result, which ultimately leads to unrealistic soil shear strength. The experimental work replaced the traditional jaw type grips by innovative 3D-printed mold or metal ring with silicone, epoxy, and hot-glue to ensure a minimal degree of damage to the roots. Other scopes of the study include a comparison between fresh and refrigerated samples, the effect of sample storage temperature, pH, and Optimum Effective Root Area (OERA) per unit area of soil. Initial study conducted on the Bermuda grass (Cynodon dactylon) roots involved comparison for different approaches based on the gripping technic to select the best method. Finally, the paper included the results of tensile strength test performed on Spartina alterniflora root samples following the suggested guidelines thus helping better evaluation of root embedded soil shear strength, enhancing the resistance against soil erosion, and conserving the ecosystem.

关键词： Root sampling Root Tensile Strength Soil Shear Strength Soil Erosion Prevention Protocol Development Restore Ecosystem

Standardization of Leaf sampling Technique in Jackfruit Nutrient Status Diagnosis

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Agricultural Sciences 2015年第2期6卷 232-237页

作者： Yan Sun Jianfeng Yang Hua Wang Chao Zu Lehe Tan Gang Wu Spice and Beverage Research Institute Chinese Academy of Tropical Agricultural Sciences Wanning China Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops Ministry of Agriculture Wanning China Hainan Provincial Key Laboratory of Genetic Improvement and Quality Regulation for Tropical Spice and Beverage Crops Wanning China

In China, little information is known about the nutrient requirements of jackfruits and the traditional nutrient management usually depends on the experience. Therefore, in this study, an attempt was made to standardize the leaf sampling technique and the suitable range of leaf nutrient concentrations for jackfruit (Artocarpus heterophyllus Lam.) nutrient status diagnosis. The sampling result was affected by canopy height, leaf age and time of sampling. Therefore, the three factors were studied. The results illustrated that the stability in level of nutrient concentrations was in 3 - 6 month-old leaves from the central part of the canopy. The most stable period was from April to May for leaf sampling. It was recommended that the stable intracanopy and stable period of nutrient concentrations could be used as the standards of leaf sampling technique. Based on the leaf sampling technique, the standard of leaf nutrient concentrations was summarized, and could be used as the standard of nutrient suitability evaluation.

关键词： Jackfruit Nutrient Status Diagnosis Leaf sampling Technique Standardization

Estimation of Population Variance Using the Coefficient of Kurtosis and Median of an Auxiliary Variable under Simple Random sampling

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Open Journal of Statistics 2017年第6期7卷 944-955页

作者： Tonui Kiplangat Milton Romanus Otieno Odhiambo George Otieno Orwa Pan African University Institute for Basic Sciences Technology and Innovation (PAUISTI) Nairobi Kenya Department of Statistics and Actuarial Science Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya

In this study we have proposed a modified ratio type estimator for population variance of the study variable y under simple random sampling without replacement making use of coefficient of kurtosis and median of an auxiliary variable x. The estimator’s properties have been derived up to first order of Taylor’s series expansion. The efficiency conditions derived theoretically under which the proposed estimator performs better than existing estimators. Empirical studies have been done using real populations to demonstrate the performance of the developed estimator in comparison with the existing estimators. The proposed estimator as illustrated by the empirical studies performs better than the existing estimators under some specified conditions i.e. it has the smallest Mean Squared Error and the highest Percentage Relative Efficiency. The developed estimator therefore is suitable to be applied to situations in which the variable of interest has a positive correlation with the auxiliary variable.

关键词： Modified Ratio Type Variance Estimator Study Variable Auxiliary Variable Kurtosis Median Bias Mean Squared Error (MSE) Percentage Relative Efficiency (PRE) Simple Random sampling

The Quality of Medicines in Community Pharmacies in Riyadh, Saudi Arabia: A Lot Quality Assurance sampling (LQAS)-Based Survey

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Pharmacology & Pharmacy 2013年第7期4卷 511-519页

作者： Hani M. J. Khojah Henrik Pallos Naoko Yoshida Manabu Akazawa Hirohito Tsuboi Kazuko Kimura Department of Drug Management and Policy Graduate School of Natural Science and Technology Kanazawa University Kana-zawa Japan Department of Drug Management and Policy Graduate School of Natural Science and Technology Kanazawa University Kana-zawa Japan Department of Drug Management and Policy Graduate School of Natural Science and Technology Kanazawa University Kana-zawa Japan Department of Clinical and Hospital Pharmacy College of Pharmacy Taibah University Madinah KSA Department of International Pharmaceutical Sciences Graduate School of Natural Science and Technology Kanazawa University Kanazawa Japan Department of Public Health and Epidemiology Meiji Pharmaceutical University Kiyose Japan

Objectives: To classify community pharmacies (CPs) in Riyadh, Saudi Arabia, in terms of the quality of medicines sold by them, using?the lot quality assurance sampling (LQAS) technique with a predefined threshold. Methods: Riyadh CPs were divided into 2 categories (“lots” for the purpose of LQAS), i.e., chain and independent CPs. Upper and lower rate thresholds for CPs that sell low-quality medicines were predefined as 20% and 5%, respectively. Consumer and provider risks were predefined as 0.05 and 0.10, respectively. The calculated number of randomly selected CPs required in each lot was 36;then, sale of low-quality medicines in >3 CPs implies a prevalence of >20% of such CPs according to LQAS. A randomly selected brand of amoxicillin (selected as a quality indicator of medicines because it is both widely counterfeited and heat-sensitive) was purchased from each pharmacy by a “mystery shopper”, checked for authenticity, and analyzed for drug content and content uniformity using a validated HPLC method. Results: Substandard amoxicillin was purchased in 9 pharmacies (4 chains and 5 independent). Both lots were thus rejected as unacceptable, which may indicate that consumers in Riyadh are at risk of purchasing substandard medicines at CPs. Conclusions: The quality of medicines sold in CPs in Riyadh did not meet our acceptability criterion, and appropriate intervention by decision makers is recommended. LQAS proved to be a practical, economical, and statistically valid sampling method for surveying the quality of medicines. It should enable decision makers to allocate resources for improvement more efficiently.

关键词： Amoxicillin Antibiotic Quality of Medicines Lot Quality Assurance sampling Saudi Arabia Community Pharmacy

A Note on the Precision of Stratified Systematic sampling

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Open Journal of Statistics 2015年第2期5卷 104-112页

作者： Akeem O. Kareem Isaac O. Oshungade Gafar M. Oyeyemi Institute for Security Studies Abuja Nigeria Department of Statistics University of Ilorin Ilorin Nigeria

Conflicting views had greeted the use of systematic sampling for sample selection and estimation in stratified sampling in terms of the precision of the population mean base on the inherent characteristics of the population. These conflicting views were analyzed using Cochran data (1977, p. 211) [1]. When the population units are ordered, variance of systematic sampling for all possible systematic samples provides equal, non-negative and most precise estimates for all the variance functions considered i.e. , unlike when a single systematic sample is used and when variance of simple random sampling is used to estimate selected systematic samples.

关键词： Precision Systematic sampling Stratified Systematic sampling Systematic Random Estimator

Toward Estimating the Variance in Acoustic Surveys Based on sampling Design

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Open Journal of Marine Science 2011年第1期1卷 1-17页

作者： Magnar Aksland 不详

This paper develops a sampling method to estimate the integral of a function of the area with a strategy to cover the area with parallel lines of observation. This sampling strategy is special in that lines very close to each other are selected much more seldom than under a uniformly random design for the positions of the parallel lines. It is also special in that the positions of some of the lines are deterministic. Two different variance estimators are derived and investigated by sampling different man made signal functions. They show different properties in that the estimator that estimate the biggest variance gives an error interval that, in some situations, may be more than ten times the error interval computed from the other estimator. It is also obvious that the second estimator underestimates the variance. The author has not succeeded to derive an expression for the expectation of this estimator. This work is motivated towards finding the variance of acoustic abundance estimates.

关键词： Acoustic Abundance Estimation Line Surveys sampling Design sampling in the Area Variance Estimation

Effect of Terrestrial LiDAR Point sampling Density in Ephemeral Gully Characterization

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Open Journal of Modern Hydrology 2013年第1期3卷 38-49页

作者： Henrique G. Momm Ronald L. Bingner Robert R. Wells Seth M. Dabney Lyle D. Frees Department of Geosciences Middle Tennessee State University Murfreesboro USA National Sedimentation Laboratory United States Department of Agriculture—Agricultural Research Service Oxford USA United States Department of Agriculture—Natural Resources Conservation Service Salina USA

Gully erosion can account for significant volumes of sediment exiting agricultural landscapes, but is difficult to monitor and quantify its evolution with traditional surveying technology. Scientific investigations of gullies depend on accurate and detailed topographic information to understand and evaluate the complex interactions between field topography and gully evolution. Detailed terrain representations can be produced by new technologies such as terrestrial LiDAR systems. These systems are capable of collecting information with a wide range of ground point sampling densities as a result of operator controlled factors. Increasing point density results in richer datasets at a cost of increased time needed to complete field surveys. In large research watersheds, with hundreds of sites being monitored, data collection can become costly and time consuming. In this study, the effect of point sampling density on the capability to collect topographic information was investigated at individual gully scale. This was performed through the utilization of semi-variograms to produce overall guiding principles for multi-temporal gully surveys based on various levels of laser sampling points and relief variation (low, moderate, and high). Results indicated the existence of a point sampling density threshold that produces little or no additional topographic information when exceeded. A reduced dataset was created using the density thresholds and compared to the original dataset with no major discrepancy. Although variations in relief and soil roughness can lead to different point sampling density requirements, the outcome of this study serves as practical guidance for future field surveys of gully evolution and erosion.

关键词： Ephemeral Gully Ground-Based LiDAR Soil Erosion Point sampling Density Remote Sensing

A Hybrid Importance sampling Algorithm for Estimating VaR under the Jump Diffusion Model

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Journal of Software Engineering and Applications 2009年第4期2卷 301-307页

作者： Tian-Shyr Dai Li-Min Liu 不详

Value at Risk (VaR) is an important tool for estimating the risk of a financial portfolio under significant loss. Although Monte Carlo simulation is a powerful tool for estimating VaR, it is quite inefficient since the event of significant loss is usually rare. Previous studies suggest that the performance of the Monte Carlo simulation can be improved by impor-tance sampling if the market returns follow the normality or the distributions. The first contribution of our paper is to extend the importance sampling method for dealing with jump-diffusion market returns, which can more precisely model the phenomenon of high peaks, heavy tails, and jumps of market returns mentioned in numerous empirical study papers. This paper also points out that for portfolios of which the huge loss is triggered by significantly distinct events, naively applying importance sampling method can result in poor performance. The second contribution of our paper is to develop the hybrid importance sampling method for the aforementioned problem. Our method decomposes a Monte Carlo simulation into sub simulations, and each sub simulation focuses only on one huge loss event. Thus the perform-ance for each sub simulation is improved by importance sampling method, and overall performance is optimized by determining the allotment of samples to each sub simulation by Lagrange’s multiplier. Numerical experiments are given to verify the superiority of our method.

关键词： Hybrid Importance sampling VaR Straddle Options Jump Diffusion Process

Assessment of Random Recruitment Assumption in Respondent-Driven sampling in Egocentric Network Data

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Social Networking 2012年第2期1卷 13-21页

作者： Hongjie Liu Jianhua Li Toan Ha Jian Li Department of Epidemiology and Biostatistics School of Public Health University of Maryland College Park USA Yunnan Institute for Drug Abuse Kunming Yunnan China

One of the key assumptions in respondent-driven sampling (RDS) analysis, called “random selection assumption,” is that respondents randomly recruit their peers from their personal networks. The objective of this study was to verify this assumption in the empirical data of egocentric networks. Methods: We conducted an egocentric network study among young drug users in China, in which RDS was used to recruit this hard-to-reach population. If the random recruitment assumption holds, the RDS-estimated population proportions should be similar to the actual population proportions. Following this logic, we first calculated the population proportions of five visible variables (gender, age, education, marital status, and drug use mode) among the total drug-use alters from which the RDS sample was drawn, and then estimated the RDS-adjusted population proportions and their 95% confidence intervals in the RDS sample. Theoretically, if the random recruitment assumption holds, the 95% confidence intervals estimated in the RDS sample should include the population proportions calculated in the total drug-use alters. Results: The evaluation of the RDS sample indicated its success in reaching the convergence of RDS compositions and including a broad cross-section of the hidden population. Findings demonstrate that the random selection assumption holds for three group traits, but not for two others. Specifically, egos randomly recruited subjects in different age groups, marital status, or drug use modes from their network alters, but not in gender and education levels. Conclusions: This study demonstrates the occurrence of non-random recruitment, indicating that the recruitment of subjects in this RDS study was not completely at random. Future studies are needed to assess the extent to which the population proportion estimates can be biased when the violation of the assumption occurs in some group traits in RDS samples.

关键词： Respondent-Driven sampling Random Selection Assumption Egocentric Network