Research On The Grading Theory Of The Size Coefficient Of Variation In The Electronic Testing For Raw Silk

At present in our country the testing indexes in the testing standards for raw silk mainly include size variance,evenness,cleanness,and neatness.But with the popularization of the electronic testing means,overseas customers are increasingly inclined to the electronic testing and the electronic testing standards Raw Silk Enchiridion 1995 developed by the International Raw Silk Association in 1995.Thus all kinds of trade fightings become more and more violent due to different testing standards used by both sides,and these fightings cause great loss of our country whose output of raw silk is 80% of the total international trade.Therefore,the development of the electronic testing standards for raw silk is not only important to the national interests,but also determines the success or failure in the international trade of raw silk.In order to construct an international platform for the quality appraisal and trade of the raw silk more efficiently and more rationally,to get a dominate authority in the research of the international testing standards for raw silk,to protect the interest of our silk industry,it is very significant to make the study on the grading theory of the electronic testing for raw silk.In such circumstance,under the support of the governmental departments of our country,we study the basic theories in the research of the electronic testing standards for raw silk size;make a systematic study on the grading theories of the size coefficient of variation in the electronic testing for raw silk.In order to make more rational and scientific electronic standard system for raw silk, this paper studies the distribution of the C.V.of the raw silk size and its characteristics. According to the sampling and grading theory of the raw silk,the paper also proposes the method to make a grading standard with the C.V.of the raw silk size as the quality index and the corresponding grading scheme on the basis of large amount of testing data of all kinds of raw silk by Uster Tester,verifies the grading scheme by simulation testing.The main work and results of the paper are as follows:1.The paper studies the distribution of the C.V.of random sample from a correlated normal population,gives its sampling distribution and its characteristics,and analyzes the effects of the characteristics of the normal population and the sample size on the shape of the sampling distribution and the characteristics of the C.V..And the study of the sampling distribution of the C.V.will not only be a very significant supplement and perfection to the theory of the sampling distribution of the C.V.in the field of probability,but affords theoretical basis for the development of the grading standard for the C.V.of the raw silk size.2.Based on the distribution of the C.V.of random sample,this paper studies the distribution of the C.V.of the continuous sample from the correlated normal population for the sample value of the raw silk size in the raw silk testing is continuously changed. Using equivalent sample,this paper gives the distribution of the C.V.of the sampling silk segment from the correlated normal population and its characteristics.And the corresponding simulation testing proves that the equivalent distribution has a good representation to the distribution of the C.V.of the sample in actual sampling testing.At the same time the paper also discusses the effects of all kinds of affecting factors on the error caused by the equivalent method.3.The problem of sample size in the electronic raw silk testing is fully discussed.By simulation,the rational range of the sample size is studied.In the testing system adopted by this study,the relative testing error will be smaller and the testing efficiency will be higher when the sampling length of the silk segment varies between 800 and 1000 meters, the number of the sampling bobbins varies between 30 and 40,thus we can get a rational sampling method.4.Using the ratio formula of the size variance of the raw silk,the paper analyzes the relation between the C.V.of the raw silk size with different testing length,studies how to estimate the two parameters(mimetic period T and attenuation rateλ) of the size fluctuation of raw silk,gives the relation between the coefficients of variation of the silk segments with different testing length.5.According to the above sampling distribution of the C.V.and the sampling method, this paper studies the grade making theory and the grading method of the C.V.of the raw silk size.By theoretical analysis and the actual testing data,the sampling distributions of the C.V.of silk segments with different testing length are given,and the calculating formulas of the grading precision and the grading boundaries are also given.Finally the paper proposes the grading schemes of raw silk with different specification,and verifies the rationality and accuracy of the grading scheme by simulation.6.The paper also studies the characteristics and the grading of the difference of the size evenness among the sampled bobbins,namely,the fluctuation of the C.V..Thus the paper gives the approximately distribution of the coefficient of variation of the C.V.and the expression of its grading precision,proposes its grading scheme,and verifies the rightness of the grading scheme by simulation.