Fast Initial Response Research Articles

Demerit-Double Exponentially Weighted Moving Average Control Chart with Fast Initial Response

Demerit-Double Exponentially Weighted Moving Average Control Chart with Fast Initial Response

On the performance of the conditional decision procedure in geometric charts

To improve the performance of control charts the conditional decision procedure (CDP) incorporates a number of previous observations into the chart’s decision rule. It is expected that charts with this runs rule are more sensitive to shifts in the process parameter. To signal an out-of-control condition more quickly some charts use a headstart feature. They are referred as charts with fast initial response (FIR). The CDP chart can also be used with FIR. In this article we analyze and compare the performance of geometric CDP charts with and with no FIR. To do it we model the CDP charts with a Markov chain and find closed-form ARL expressions. We find the conditional decision procedure useful when the fraction p of nonconforming units deteriorates. However the CDP chart is not very effective for signaling decreases in p.

Improving the performance of CUSUM charts

AbstractThe control chart is an important statistical technique that is used to monitor the quality of a process. Shewhart control charts are used to detect larger disturbances in the process parameters, whereas CUSUM and EWMA charts are meant for smaller and moderate changes. Runs rules schemes are generally used to enhance the performance of Shewhart control charts. In this study, we propose two runs rules schemes for the CUSUM charts. The performance of these two schemes is compared with the usual CUSUM, the weighted CUSUM, the fast initial response CUSUM and the usual EWMA schemes. The comparisons revealed that the proposed schemes perform better for small and moderate shifts, whereas they reasonably maintain their efficiency for large shifts as well. Copyright © 2010 John Wiley & Sons, Ltd.

Bacterial Chemotaxis in an Optical Trap

An optical trapping technique is implemented to investigate the chemotactic behavior of a marine bacterial strain Vibrio alginolyticus. The technique takes the advantage that the bacterium has only a single polar flagellum, which can rotate either in the counter-clock-wise or clock-wise direction. The two rotation states of the motor can be readily and instantaneously resolved in the optical trap, allowing the flagellar motor switching rate to be measured under different chemical stimulations. In this paper the focus will be on the bacterial response to an impulsive change of chemoattractant serine. Despite different propulsion apparati and motility patterns, cells of V. alginolyticus apparently use a similar response as Escherichia coli to regulate their chemotactic behavior. Specifically, we found that the switching rate of the bacterial motor exhibits a biphasic behavior, showing a fast initial response followed by a slow relaxation to the steady-state switching rate . The measured can be mimicked by a model that has been recently proposed for chemotaxis in E. coli. The similarity in the response to the brief chemical stimulation in these two different bacteria is striking, suggesting that the biphasic response may be evolutionarily conserved. This study also demonstrated that optical tweezers can be a useful tool for chemotaxis studies and should be applicable to other polarly flagellated bacteria.

ZnO Modified High Aspect Ratio Carbon Electrodes for Hydrogen Sensing Applications

Design, fabrication, and testing results of a hydrogen gas sensor based on a surface modified high density and high aspect ratio 3-D carbon post microarray are described in this paper. After the conversion of photoresist patterns into carbon electrodes, the increased surface was conformally coated with a metal oxide semiconductor film by atomic layer deposition (ALD). A maximum sensitivity as high as 100 (Rair/ Rhydrogen) has been observed in the fabricated sensor even in the presence of moisture at low temperature. A fast initial response (90% resistance drop in 30sec at 3000ppm hydrogen) of the sensor could be utilized for early leak detection. The methodology of surface modification as well as the test result shows good promise for various chemical sensing devices based on the proposed strategy.

Enhancing the performance of EWMA charts

Control charts are extensively used in processes and are very helpful in determining the special cause variations so that a timely action may be taken to eliminate them. One of the charting procedures is the Shewhart‐type control charts, which are used mainly to detect large shifts. Two alternatives to the Shewhart‐type control charts are the cumulative (CUSUM) control charts and the exponentially weighted moving average (EWMA) control charts that are specially designed to detect small and moderately sustained changes in quality. Enhancing the ability of design structures of control charts is always desirable and one may do it in different ways. In this article, we propose two runs rules schemes to be applied on EWMA control charts and evaluate their performance in terms of the Average Run Length (ARL). Comparisons of the proposed schemes are made with some existing representative CUSUM and EWMA‐type counterparts used for small and moderate shifts, including the classical EWMA, the classical CUSUM, the fast initial response CUSUM and EWMA, the weighted CUSUM, the double CUSUM, the distribution‐free CUSUM and the runs rules schemes‐based CUSUM. The findings of the study reveal that the proposed schemes are able to perform better than all the other schemes under investigation. Copyright © 2010 John Wiley & Sons, Ltd.

The Run Sum R Chart with Fast Initial Response

A fast initial response (FIR) feature for the run sum R chart is proposed and its ARL performance estimated by a Markov chain representation. It is shown that this chart is more sensitive than several R charts with runs rules proposed by different authors. We conclude that the run sum R chart is simple to use and a very effective tool for monitoring increases and decreases in process dispersion.

Spatial clustering and hierarchical coding in immediate serial recall

Four experiments are reported that demonstrate the benefits of clustering by spatial proximity in spatial serial recall and provide support for the notion that hierarchical coding underpins the retention of clustered sequences in spatial working memory. Sequences segregated by spatial clusters increased serial recall performance at different levels of sequence length in a variation of the Corsi test and produced a faster initial response time (RT), which indicates that they afforded data reducing processes. RT at cluster boundary increased in parallel with the number of items forming the clusters, suggesting that subroutines of different length were responsible for the ordering of items within clusters of different size. Evidence for hierarchical coding was also obtained in a serial recognition task, indicating this type of representation pertains to the retention of the sequences rather than exclusively to the organisation of the motor plan for the reproduction of the sequences.

평판형 전자기 엑츄에이터의 초기응답속도 향상을 위한 쇼티트 턴에 관한 연구

기존의 평판형 전자기 엑츄에이터에 쇼티드 턴을 적용한 새로운 형태의 평판형 전자기 엑츄에이터를 제안하였다. 기존의 평판형 전자기 엑츄에이터에서 발생하는 인덕턴스에 의한 초기응답 지연현상을 줄이기 위해 본 논문에서는 기존의 엑츄에이터의 요크와 요크 사이에 중간요크(center yoke)를 추가하고, 쇼티드 턴을 적용한 새로운 형태의 평판형 전자기 엑츄에이터를 제안 하고, 상용 자기장 해석 프로그램인 MAXWELL을 이용한 시뮬레이션을 통해 동적 성능 향상을 검증 하였다. This paper presents the new design of flat electromagnetic actuator. Novel shorted turn and copper center pole are placed into existent design in order to reduce the inductance of coil and accelerate the initial response. Finite element analysis using commercial electromagnetic solver “MAXWELL” is performed to simulate the improvement of dynamic characteristics such as fast initial response and so on.

Generally weighted moving average control charts with fast initial response features

The generally weighted moving average (GWMA) control chart is an extension model of exponentially weighted moving average (EWMA) control chart. Recently, some approaches have been proposed to modify EWMA charts with fast initial response (FIR) features. We introduce these approaches in GWMA-type charts. Via simulation, various control schemes are designed and then their average run lengths are computed and compared. Based on the overall performance, it is showed that the DGWMA chart is the best choice especially when the shift is moderate, and the GWMA charts provided with additional FIR feature have a good performance only in detecting large shifts during the initial stage.

Fast Initial Response Features for Poisson GWMA Control Charts

The Poisson GWMA (PGWMA) control chart is an extension model of Poisson EWMA chart. It is substantially sensitive to small process shifts for monitoring Poisson observations. Recently, some approaches have been proposed to modify EWMA charts with fast initial response (FIR) features. In this article, we employ these approaches in PGWMA charts and introduce a novel chart called Poisson double GWMA (PDGWMA) chart for comparison. Using simulation, various control schemes are designed and their average run lengths (ARLs) are computer and compared. It is shown that the PDGWMA chart is the first choice in detecting small shifts especially when the shifts are downward, and the PGWMA chart with adjusted time-varying control limits performs excellently in detecting great process shifts during the initial stage.

The Neurovascular Coupling Bears Properties of a Feedforward and Feedback Regulative Mechanism

Temporal profiles of mediators involved in the neurovascular coupling bear feedforward and feedback characteristics, which are supported by mathematical modeling of evoked hemodynamic responses. However, cerebral autoregulation was expressed as a feedback control system. Therefore, question of overdetermination of the neurovascular coupling model arises. Addressing this issue, we analyzed both models for their appropriateness in describing the neurovascular coupling. Visually evoked flow velocities were recorded from healthy volunteers (aged 24.7 ± 1.6 SD; 9 females, 11 males) with transcranial Doppler in the posterior cerebral artery. Control system parameters of the two models were specified according to the least-square-fitting technique. Mean square errors between measured and modeled curves and Akaike’s information criterion (AIC) supported the feedforward-feedback model. Mean square differences decreased from 27.2 ± 37.9 to 2.3 ± 2 and the AIC from 2.7 ± 0.6 % 2 to 2 ± 0.3 % 2. The feedforward element increased the accuracy of the control system model in describing the fast initial response. Biologically, the parameter decreases the initial mismatch between the fast neuronal but slow vascular response because of visual activation. (E-mail: bernhard.rosengarten@neuro.med.uni-giessen.de)

G-CSF Control of Neutrophils Dynamics in the Blood

White blood cell neutrophil is a key component in the fast initial immune response against bacterial and fungal infections. Granulocyte colony stimulating factor (G-CSF) which is naturally produced in the body, is known to control the neutrophils production in the bone marrow and the neutrophils delivery into the blood. In oncological practice, G-CSF injections are widely used to treat neutropenia (dangerously low levels of neutrophils in the blood) and to prevent the infectious complications that often follow chemotherapy. However, the accurate dynamics of G-CSF neutrophil interaction has not been fully determined and no general scheme exists for an optimal G-CSF application in neutropenia. Here we develop a two-dimensional ordinary differential equation model for the G-CSF-neutrophil dynamics in the blood. The model is built axiomatically by first formally defining from the biology the expected properties of the model, and then deducing the dynamic behavior of the resulting system. The resulting model is structurally stable, and its dynamical features are independent of the precise form of the various rate functions. Choosing a specific form for these functions, three complementary parameter estimation procedures for one clinical (training) data set are utilized. The fully parameterized model (6 parameters) provides adequate predictions for several additional clinical data sets on time scales of several days. We briefly discuss the utility of this relatively simple and robust model in several clinical conditions.

The random intrinsic fast initial response of two-sided CUSUM charts

Abstract This article analyses the performance of a one-sided cumulative sum (CUSUM) chart that is initialized using a random starting point following the natural or intrinsic probability distribution of the CUSUM statistic. By definition, this probability distribution remains stable as the chart is used. The probability that the chart starts at zero according to this intrinsic distribution is always smaller than one, which confers on the chart a fast initial response feature. The article provides a fast and accurate algorithm to compute the in-control and out-of-control average run lengths and run-length probability distributions for one-sided CUSUM charts initialized using this random intrinsic fast initial response (RIFIR) scheme. The algorithm also computes the intrinsic distribution of the CUSUM statistic and random samples extracted from this distribution. Most importantly, no matter how the chart was initialized, if no level shifts and no alarms have occurred before time τ > 0, the distribution of ...

Sigma-mean monitoring for the local area augmentation of GPS

The local area augmentation system (LAAS) is a ground-based differential GPS system being developed to support aircraft precision approach and landing navigation with guaranteed integrity. To quantitatively appraise navigation integrity, an aircraft computes vertical and lateral protection levels using the standard deviation of pseudo-range correction errors, /spl sigma//sub pr/spl I.bar/gnd/, broadcast by the LAAS ground facility (LGF). Thus, one significant integrity risk is that the true standard deviation (sigma) of the pseudo-range correction error distribution may grow to exceed the broadcast correction error sigma or that the true mean of the correction error distribution becomes excessive during LAAS operation. This event may occur due to unexpected anomalies of GPS measurements. To insure that the true error distribution is bounded by a zero-mean Gaussian distribution with the broadcast sigma value, real-time sigma and mean monitoring is necessary. Both direct estimation and cumulative sum (CUSUM) methods are useful to detect violations with acceptable residual integrity risk. For sigma monitoring, the estimation method more rapidly detects small violations of /spl sigma//sub pr/spl I.bar/gnd/ but the fast initial response (FIR) CUSUM variant more promptly detects significant violations that would pose a larger threat to user integrity. For the purposes of mean monitoring, the FIR CUSUM variant is superior to the estimation method in detecting any mean violations. The results demonstrate that real-time protection is achievable against all sizes of sigma/mean failures that can threaten navigation integrity.

Frequency response characteristics of sympathetic and autoregulatory vasomotor responses in the kidney and hindlimb

The literature suggests vasomotor responses might be faster in the kidney than in other vascular beds. We compared vasoconstrictor response times to sympathetic nerve stimulation (SNS) as well as autoregulatory responses (AR) to a 20 mmHg step increase of perfusion pressure in the kidney and hindlimb of anesthetized rats. SNS of renal and lumbar nerves (1–8 Hz for 60 s) led to similar reductions in renal (RBF, −59% at 8 Hz) and iliac blood flow (IBF, −64% at 8 Hz). RBF fell biphasically with a rapid component within 3–5 s (τ =3.0 s) and a slower one over 30–50 s (τ =11 s), both contributing equally. In contrast, IBF fell monophasically within 3–5 s (τ =1.5 s). Dynamic modulation of SNS (~5 Hz, Delta;t on, Delta;t off, Delta;t=1, 2, 3, 4, 8, 15, 60 s) showed similar corner frequencies for RBF and IBF at ~0.15 Hz and an additional one for RBF at ~0.05 Hz. AR responses displayed a bimodal adaptation of RBF with a fast initial response within 9 s (τ =3.3 s) providing 38% AR efficiency, and a subsequent slower response within 30–120 s bringing total AR to 100%. Previous studies support the fast response of AR reflecting the myogenic response and the secondary tubuloglomerular feedback (TGF). AR in IBF displayed only one component (τ =2.5 s) providing 34% AR efficiency. It is concluded that the fast components of SNS and AR vasoconstrictor responses are of similar speed in kidney and skeletal muscle. In addition, secondary slower mechanisms operate in the kidney reducing the speed of overall RBF adaptation. Whether the secondary component in the SNS response is the same as TGF in AR requires further study. Supported by NIH (HL02334) and Guyton Award for Excell. in Integr. Physiol..

The random intrinsic fast initial response of one-sided CUSUM charts

This article analyses the performance of a one-sided cumulative sum (CUSUM) chart that is initialized using a random starting point following the natural or intrinsic probability distribution of the CUSUM statistic. By definition, this probability distribution remains stable as the chart is used. The probability that the chart starts at zero according to this intrinsic distribution is always smaller than one, which confers on the chart a fast initial response feature. The article provides a fast and accurate algorithm to compute the in-control and out-of-control average run lengths and run-length probability distributions for one-sided CUSUM charts initialized using this random intrinsic fast initial response (RIFIR) scheme. The algorithm also computes the intrinsic distribution of the CUSUM statistic and random samples extracted from this distribution. Most importantly, no matter how the chart was initialized, if no level shifts and no alarms have occurred before time τ > 0, the distribution of the run length remaining after τ is provided by this algorithm very accurately, provided that τ is not too small.

Fast initial response features for EWMA control charts

The exponentially weighted moving average (EWMA) control chart became very popular during the last decade. It is characterized by simple handling and good performance. It turns out, however, that the most popular EWMA scheme with fixed-width control limits—the asymptotic control limits are taken and do not change over time—detects early changes rather slowly. For the competing CUSUM chart the so-called fast initial response (head-start) feature is developed which permits rapid response to an initial out-of-control situation. Meanwhile, in some papers similar modifications for EWMA schemes are described. We compare these approaches by using precise computation techniques, which are based on numeric quadrature rules and allow higher accuracy than earlier studies. Moreover, previous comparisons are restricted to the evaluation of the detection speed by comparing the average run lengths (ARLs), that is, the parameter of interest is constant during the whole monitoring period. Here, we consider more possible change point locations, which gives the EWMA control chart user a better insight into the scheme performance for early changes. *** DIRECT SUPPORT *** A00T7005 00004

Use of risk-adjusted CUSUM and RSPRT charts for monitoring in medical contexts.

In this paper we discuss the use of charts derived from the sequential probability ratio test (SPRT): the cumulative sum (CUSUM) chart, RSPRT (resetting SPRT), and FIR (fast initial response) CUSUM. The theoretical development of the methods is described and some considerations one might address when designing a chart, explored, including the approximation of average run lengths (ARLs), the importance of detecting improvements in a process as well as detecting deterioration and estimation of the process parameter following a signal. Two examples are used to demonstrate the practical issues of quality control in the medical setting, the first a running example and the second a fully worked example at the end of the paper. The first example relates to 30-day mortality for patients of a single cardiac surgeon over the period 1994-1998, the second to patient deaths in the practice of a single GP, Harold Shipman. The charts' performances relative to each other are shown to be sensitive to the definition of the 'out of control' state of the process being monitored. In light of this, it is stressed that a suitable means by which to compare charts is chosen in any specific application.

EWMA Schemes with Nonhomogeneous Transition Kernels

In the last decades, various methods are applied for evaluating different performance measures of change-point detection schemes. In only some cases—recent examples are Chandrasekaran et al. (Chandrasekaran, S.; English, J.R.; Disney, R.L. Modeling and analysis of EWMA control schemes with variance-adjusted control limits. IIE Transactions 1995, 277, 282–290) and Steiner (Steiner, S.H. EWMA control charts with time-varying control limits and fast initial response. Journal of Quality Technology 1999, 31 (1), 75–86)—EWMA schemes with varying control limits are considered. However, EWMA charts with just these limits are sometimes more appropriate than those with fixed limits. Here, a computational approach is presented which allows to compute the usual performance measures with high precision. The main idea is connected to earlier results of Madsen and Conn (Madsen, R.W.; Conn, P.S. Ergodic behavior for nonnegative kernels. Ann. Probab. 1973, 1, 995–1013), Woodall (Woodall, W.H. The distribution of the run length of one-sided CUSUM procedures for continuous random variables. Technometrics 1983, 25, 295–301), and Waldmann (Waldmann, K.-H. Bounds for the distribution of the run length of geometric moving average charts. J. R. Stat. Soc., Ser. C, Appl. Stat. 1986a, 35, 151–158). Additionally, quantities as the steady-state ARL and the steady-state distribution of the chart statistic can be computed very precisely.