The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
S Chakraborti - One of the best experts on this subject based on the ideXlab platform.
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a phase ii nonparametric control chart based on precedence statistics with runs type signaling rules
Computational Statistics & Data Analysis, 2009Co-Authors: S Chakraborti, Serkan Eryilmaz, Schalk William HumanAbstract:Nonparametric control charts do not require knowledge about the shape of the underlying distribution and can thus be attractive in certain situations. Two new Shewhart-type nonparametric control charts are proposed for monitoring the unknown location parameter of a continuous population in Phase II (prospective) applications. The charts are based on control limits given by two specified order statistics from a reference sample, obtained from a Phase I (retrospective) analysis, and using some runs-type signaling rules. The plotting statistic can be any order statistic in a Phase II sample; the median is used here for simplicity and robustness. Exact run length distributions of the proposed charts are derived using conditioning and some results from the theory of runs. Tables are provided for practical implementation of the charts for a given in-control average run length (ARL"0) between 300 and 500. Comparisons of the average run length ARL, the standard deviation of run length (SDRL) and some run length percentiles show that the charts have robust in-control performance and are more efficient when the underlying distribution is t (symmetric with heavier tails than the normal) or gamma (1, 1) (right-skewed). Even for the normal distribution, the new charts are quite competitive. An illustrative numerical example is given. An added advantage of these charts is that they can be applied before all the data are collected which might lead to savings in time and resources in certain applications.
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run length distribution and percentiles the shewhart x chart with unknown parameters
Quality Engineering, 2007Co-Authors: S ChakrabortiAbstract:[This abstract is based on the author’s abstract.]Important information concerning the performance of control charts may be missed by focusing too much on the average run length, since the run length distribution is usually highly right-skewed. Examinat..
Michael B C Khoo - One of the best experts on this subject based on the ideXlab platform.
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an alternative design for the variable sample size coefficient of variation chart based on the median run length and expected median run length
International Journal of Industrial Engineering-theory Applications and Practice, 2019Co-Authors: Sok Li Lim, Wai Chung Yeong, Michael B C Khoo, Zhi Lin Chong, Khai Wah KhawAbstract:Control charts for monitoring the coefficient of variation (CV) are attracting increasing attention in recent years. These charts are able to monitor processes with an unstable mean and/or standard deviation, but has a stable CV. Existing CV charts are designed based on the average run length (ARL) criterion. However, this paper has shown that designs based on the ARL criterion could result in misinterpretation of the chart’s actual performance. Hence, this paper proposes alternative designs for the VSS CV chart, based on the median run length (MRL) and expected median run length (EMRL) criteria. This paper also compares the performance of the VSS CV chart with that of the Exponentially Weighted Moving Average (EWMA) and Shewhart CV charts, based on the proposed designs. Subsequently, this paper shows the implementation of the proposed designs on an industrial example.
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run sum chart for monitoring multivariate coefficient of variation
Computers & Industrial Engineering, 2017Co-Authors: Michael B C Khoo, Wei Lin TeohAbstract:Abstract Coefficient of variation (CV) is an important quality characteristic to take into account when the process mean and standard deviation are not constants. A setback of the existing chart for monitoring the multivariate CV is that the chart is slow in detecting a multivariate CV shift in the Phase-II process. To overcome this problem, this paper proposes a run sum chart for monitoring the multivariate CV in the Phase-II process. The average run length (ARL), standard deviation of the run length (SDRL) and expected average run length (EARL), under the zero state and steady state cases, are used to compare the performance of the proposed chart with the existing multivariate CV chart. The proposed chart’s optimal parameters are computed using the Mathematica programs, based on the Markov chain model. Two one-sided run sum charts for monitoring the multivariate CV are considered, where they can be used simultaneously to detect increasing and decreasing multivariate CV shifts. The effects of different in-control CV values, number of regions, shift and sample sizes, and number of variables being monitored are studied. The implementation of the proposed chart is illustrated with an example using the data dealing with steel sleeve inside diameters.
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the double sampling s2 chart with estimated process variance
Communications in Statistics-theory and Methods, 2017Co-Authors: Philippe Castagliola, Pedro Carlos Oprime, Michael B C KhooAbstract:ABSTRACTThis paper proposes useful exact bounds for the parameters of the double sampling S2 chart with known process variance and it also investigates the properties of the double sampling S2 chart with estimated process variance, in terms of the average run length, the standard deviation of the run length and the average sample size, providing a numerical comparison with the known process variance case. It also provides guidelines to systematically design the double sampling S2 chart both with known and estimated process variance and proposes two optimal design procedures with estimated process variance, for (a) minimizing the out-of-control average run length and (b) minimizing the out-of-control average sample size.
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performance measures for the shewhart x bar control chart
Quality Engineering, 2004Co-Authors: Michael B C KhooAbstract:[This abstract is based on the author's abstract.] When using a Shewhart X-bar control chart in process monitoring, interpretations based on the average run length can be misleading because the in-control run length distribution of the chart is highly s..
G Lakhani - One of the best experts on this subject based on the ideXlab platform.
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optimal huffman coding of dct blocks
IEEE Transactions on Circuits and Systems for Video Technology, 2004Co-Authors: G LakhaniAbstract:It is a well-observed characteristic that, when a discrete cosine transform block is traversed in the zigzag order, ac coefficients generally decrease in size and the runs of zero coefficients increase in length. This paper presents a minor modification to the Huffman coding of the JPEG baseline compression algorithm to exploit this characteristic. During the Run-Length coding, instead of pairing a nonzero ac coefficient with the Run-Length of the preceding zero coefficients, our encoder pairs it with the Run-Length of subsequent zeros. This small change makes it possible for our codec to code a pair using a separate Huffman code table optimized for the position of the nonzero coefficient denoted by the pair. These position-dependent code tables can be encoded efficiently without incurring a sizable overhead. Experimental results show that our encoder produces a further reduction in the ac coefficient Huffman code size by about 10%-15%.
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optimal huffman coding of dct blocks
IEEE Transactions on Circuits and Systems for Video Technology, 2004Co-Authors: G LakhaniAbstract:It is a well-observed characteristic that, when a discrete cosine transform block is traversed in the zigzag order, ac coefficients generally decrease in size and the runs of zero coefficients increase in length. This paper presents a minor modification to the Huffman coding of the JPEG baseline compression algorithm to exploit this characteristic. During the Run-Length coding, instead of pairing a nonzero ac coefficient with the Run-Length of the preceding zero coefficients, our encoder pairs it with the Run-Length of subsequent zeros. This small change makes it possible for our codec to code a pair using a separate Huffman code table optimized for the position of the nonzero coefficient denoted by the pair. These position-dependent code tables can be encoded efficiently without incurring a sizable overhead. Experimental results show that our encoder produces a further reduction in the ac coefficient Huffman code size by about 10%-15%.
Robert Wrembel - One of the best experts on this subject based on the ideXlab platform.
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rlh bitmap compression technique based on run length and huffman encoding
Information Systems, 2009Co-Authors: Michal Stabno, Robert WrembelAbstract:In this paper we propose a technique of compressing bitmap indexes for application in data warehouses. This technique, called Run-Length Huffman (RLH), is based on Run-Length encoding and on Huffman encoding. Additionally, we present a variant of RLH, called RLH-N. In RLH-N a bitmap is divided into N-bit words that are compressed by RLH. RLH and RLH-N were implemented and experimentally compared to the well-known word aligned hybrid (WAH) bitmap compression technique that has been reported to provide the shortest query execution time. The experiments discussed in this paper show that: (1) RLH-compressed bitmaps are smaller than corresponding WAH-compressed bitmaps, regardless of the cardinality of an indexed attribute, (2) RLH-N-compressed bitmaps are smaller than corresponding WAH-compressed bitmaps for certain range of cardinalities of an indexed attribute, (3) RLH and RLH-N-compressed bitmaps offer shorter query response times than WAH-compressed bitmaps, for certain range of cardinalities of an indexed attribute, and (4) RLH-N assures shorter update time of compressed bitmaps than RLH.
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rlh bitmap compression technique based on run length and huffman encoding
Data Warehousing and OLAP, 2007Co-Authors: Michal Stabno, Robert WrembelAbstract:In this paper we present a technique of compressing bitmap indexes for application in data warehouses. The developed compression technique, called Run-Length Huffman (RLH), is based on the Run-Length encoding and on the Huffman encoding. RLH was implemented and experimentally compared to the well known Word Aligned Hybrid bitmap compression technique that has been reported to provide the shortest query execution time. The experiments discussed in this paper show that RLH offers shorter query response times than WAH, for certain cardinalities of indexed attributes. Moreover, bitmaps compressed with RLH are smaller than corresponding bitmaps compressed with WAH. Additionally, we propose a modified RLH, called RLH-1024, which is designed to better support bitmap updates.
Schalk William Human - One of the best experts on this subject based on the ideXlab platform.
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a phase ii nonparametric control chart based on precedence statistics with runs type signaling rules
Computational Statistics & Data Analysis, 2009Co-Authors: S Chakraborti, Serkan Eryilmaz, Schalk William HumanAbstract:Nonparametric control charts do not require knowledge about the shape of the underlying distribution and can thus be attractive in certain situations. Two new Shewhart-type nonparametric control charts are proposed for monitoring the unknown location parameter of a continuous population in Phase II (prospective) applications. The charts are based on control limits given by two specified order statistics from a reference sample, obtained from a Phase I (retrospective) analysis, and using some runs-type signaling rules. The plotting statistic can be any order statistic in a Phase II sample; the median is used here for simplicity and robustness. Exact run length distributions of the proposed charts are derived using conditioning and some results from the theory of runs. Tables are provided for practical implementation of the charts for a given in-control average run length (ARL"0) between 300 and 500. Comparisons of the average run length ARL, the standard deviation of run length (SDRL) and some run length percentiles show that the charts have robust in-control performance and are more efficient when the underlying distribution is t (symmetric with heavier tails than the normal) or gamma (1, 1) (right-skewed). Even for the normal distribution, the new charts are quite competitive. An illustrative numerical example is given. An added advantage of these charts is that they can be applied before all the data are collected which might lead to savings in time and resources in certain applications.
