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United States Department of Agriculture

Agricultural Research Service

Title: A Study of Tapered Beard Sampling Method as Used in HVI

Authors
item Cai, Yiyun - LA STATE UNIV.
item Cui, Xiaoliang
item Rodgers, James
item Martin, Vikki - COTTON INC
item Watson, Mike - COTTON INC

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 23, 2008
Publication Date: June 13, 2008
Citation: Cai, Y., Cui, X., Rodgers Iii, J.E., Martin, V., Watson, M. 2008. A study of tapered beard sampling method as used in hvi. Meeting Proceedings.

Interpretive Summary: Beard method is used for sampling cotton fibers to generate fibrograms that can give length parameters. This sampling method is used by the High Volume Instrument (HVI) system for measuring cotton fiber length parameters. Nowadays HVI is extensively used because of its speed and accuracy. A fundamental issue about the beard sampling method is its bias. In other words, is the length distribution of the sampled specimen fibers the same as the distribution of the original fibers? Even though different assumptions regarding the bias have been proposed, we have seen discrepancies in measurements that cannot be explained by using these assumptions, especially in the short fiber region. Therefore, it is important to investigate the bias of the beard sampling method. In this paper we report a fundamental research, including experimental and theoretical analysis, and computer modeling, that reveals the bias due to the beard sampling method and helps us understand better how this sampling method affects the length distribution of sampled cotton fibers.

Technical Abstract: Beard method is used for sampling cotton fibers to generate fibrograms from which length parameters can be obtained. It is the sampling method used by HVI. HVI uses a fiber comb to sample cotton fibers and form a fiber beard for measuring fiber length parameters. A fundamental issue about this sampling method is its bias. There have been different assumptions regarding the bias of the beard sampling method. The original fibrogram theory for the beard method adopted an assumption that this procedure is length-biased, while other researchers later revised this assumption to that each fiber has equal probability of being sampled regardless its length (unbiased assumption). In our experiments, we have seen discrepancies in measurements that cannot be explained by using length-biased or unbiased assumptions, especially in the short fiber region. Therefore, it is important to investigate the bias of the beard method. We report a fundamental research, including experimental and theoretical analysis, and computer modeling, that reveals the bias due to this sampling method. We found that the beard sampling method as used in HVI is not completely length-biased; it is very similar to the original sample except in the short fiber region. Short fiber content by number of the sampled fiber is lower than that of the original fiber, and this difference is inherently introduced by the sampling method.

Last Modified: 10/30/2014
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