Articoli di riviste: "Interval filter"

1

Khan, Hidayat Ullah, Asghar Khan, Faiz Muhammad Khan, Amir Khan e Muhammad Taj. "A NEW VIEW OF FUZZY ORDERED SEMIGROUPS". Open Journal of Science and Technology 1, n. 1 (14 novembre 2018): 9–17. http://dx.doi.org/10.31580/ojst.v1i1.150.

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fuzzy coding theory, fuzzy finite state machines, and fuzzy languages. In this paper, we introduce the concept of an interval-valued -fuzzy filter of an ordered semigroup, where with. Since the concept of an interval-valued -fuzzy filter is an important and useful generalization of the ordinary interval-valued fuzzy filter, we discuss some fundamental aspects of an interval-valued -fuzzy filters. An interval-valued -fuzzy filter is a generalization of the existing concept of an interval-valued fuzzy filter. We discuss the concept of an interval-valued -fuzzy left (right)-filters and provide some characterization theorems. Finally, we extend the concept of an interval-valued fuzzy subgroup with thresholds to the concept of an interval-valued fuzzy left (right)-filter with thresholds of s.

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Ji, Hui, Songlin Nie e Yeqing Huang. "An interval-fuzzy two-stage stochastic programming method for filter management of hydraulic systems". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, n. 15 (9 dicembre 2014): 2788–809. http://dx.doi.org/10.1177/0954406214563737.

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An interval-fuzzy two-stage stochastic programming model for filter management of hydraulic system under uncertainties is proposed in this paper. The interval-fuzzy two-stage stochastic programming model integrates the two-stage stochastic programming, fuzzy programming, and interval parameter nonlinear programming into an optimization model of contamination control in hydraulic system. For a typical hydraulic system, it can be used for expressing the uncertainties existed in the purchase cost of filters, contamination ingression and generation rates, and contamination-holding capacity as probability functions, interval numbers, and fuzzy sets. The developed method is applied to examining the decisions on the adoption of bypass filter and selection of filters within multi-segments, multi-period, and multi-option context. All potential scenarios of filters management policy associated with different economic penalties, objectives, and reliability of system are analyzed. The results of the illustrative example show that the reasonable solutions are generated, including binary and continuous variables which help the decision maker identify optimal strategies for filter allocation and selection, planning the adoption of bypass filter under different working conditions.

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Louédec, Morgan, e Luc Jaulin. "Interval Extended Kalman Filter—Application to Underwater Localization and Control". Algorithms 14, n. 5 (29 aprile 2021): 142. http://dx.doi.org/10.3390/a14050142.

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The extended Kalman filter has been shown to be a precise method for nonlinear state estimation and is the facto standard in navigation systems. However, if the initial estimated state is far from the true one, the filter may diverge, mainly due to an inconsistent linearization. Moreover, interval filters guarantee a robust and reliable, yet unprecise and discontinuous localization. This paper proposes to choose a point estimated by an interval method, as a linearization point of the extended Kalman filter. We will show that this combination allows us to get a higher level of integrity of the extended Kalman filter.

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Ning Xiao-Lei, Wang Hong-Li, Zhang Qi e Chen Lian-Hua. "Interval diffracted particle filter". Acta Physica Sinica 59, n. 7 (2010): 4426. http://dx.doi.org/10.7498/aps.59.4426.

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Heine, Kari, e Dan Crisan. "Uniform approximations of discrete-time filters". Advances in Applied Probability 40, n. 4 (dicembre 2008): 979–1001. http://dx.doi.org/10.1239/aap/1231340161.

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Throughout recent years, various sequential Monte Carlo methods, i.e. particle filters, have been widely applied to various applications involving the evaluation of the generally intractable stochastic discrete-time filter. Although convergence results exist for finite-time intervals, a stronger form of convergence, namely, uniform convergence, is required for bounding the error on an infinite-time interval. In this paper we prove easily verifiable conditions for the filter applications that are sufficient for the uniform convergence of certain particle filters. Essentially, the conditions require the observations to be accurate enough. No mixing or ergodicity conditions are imposed on the signal process.

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Heine, Kari, e Dan Crisan. "Uniform approximations of discrete-time filters". Advances in Applied Probability 40, n. 04 (dicembre 2008): 979–1001. http://dx.doi.org/10.1017/s0001867800002937.

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Throughout recent years, various sequential Monte Carlo methods, i.e. particle filters, have been widely applied to various applications involving the evaluation of the generally intractable stochastic discrete-time filter. Although convergence results exist for finite-time intervals, a stronger form of convergence, namely, uniform convergence, is required for bounding the error on an infinite-time interval. In this paper we prove easily verifiable conditions for the filter applications that are sufficient for the uniform convergence of certain particle filters. Essentially, the conditions require the observations to be accurate enough. No mixing or ergodicity conditions are imposed on the signal process.

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Palanivel, Kaliyaperumal, Prakasam Muralikrishna, Perumal Hemavathi, Ronnason Chinram e Pattarawan Singavananda. "Interval Valued Intuitionistic Fuzzy β-Filters on β-Algebras". International Journal of Analysis and Applications 20 (26 settembre 2022): 50. http://dx.doi.org/10.28924/2291-8639-20-2022-50.

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This study establishes the concept of interval valued intuitionistic fuzzy (InVInF) β-filters on β-algebras and a few of its related properties are investigated. Some compelling results of interval valued fuzzy β-filters have been examined. Further, the notions of products and strong β-filters are also introduced. In addition that, the level set and homomorphism of interval valued intuitionistic fuzzy β-filters are too discussed. Furthermore, we enacted that the intersection between two interval valued intuitionistic fuzzy β−filters is again an interval valued intuitionistic fuzzy β-filter.

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Hujo, Ľubomír, Juraj Jablonický, Juraj Tulík, Ján Kosiba, Jerzy Kaszkowiak e Matej Michalides. "Verification Measurement of Laboratory Test Equipment for Evaluation of Technical Properties of Automotive Oil Filters". Applied Sciences 11, n. 18 (11 settembre 2021): 8435. http://dx.doi.org/10.3390/app11188435.

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By simulating the operating conditions, it is possible to verify and evaluate the technical properties of motor vehicle oil filters and the functionality of the designed equipment. Contaminated engine oil from operation was used with MANN W950/26 oil filter and a CNH Industrial 2992242 oil filter in the test circuit. Before use, the level of engine oil contamination in the test circuit was determined by evaluating the physicochemical properties. The laboratory test equipment also allows monitoring the technical life of oil filters, with variously contaminated engine oil, with the possibility of extending engine oil change service intervals depending on changes in the physicochemical properties of engine oil and filter efficiency. These laboratory tests can be performed in parallel in two hydraulic circuits, which can significantly reduce the testing time of the filter capabilities of oil filters, without the risk of engine damage, provided that the tests were performed under operating conditions. The results of the evaluation of the filtration capacity of oil filters can be used in the design of new filter materials, but also with a suitably determined methodology of oil filter replacement and engine oil change interval, it is possible to extend replacement intervals, which has a significant benefit not only from an economic but also ecological point of view. The result of the measurements is the confirmation of the functionality of the device with the possibility of simulating the operating conditions, at different degrees of oil contamination, at different operating temperatures and using different oil filters.

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Yang, Yanting, Yan Liang, Linfeng Xu, Yuemei Qin e Yanbo Yang. "Robust interval-constrained H ∞ filter". IET Control Theory & Applications 11, n. 7 (25 aprile 2017): 908–14. http://dx.doi.org/10.1049/iet-cta.2016.1472.

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Ansari, Aiysha, Padmaja Ramaiah, Lillian Collazo, Hamisu M. Salihu e Donna Haiduven. "Comparison of Visual versus Microscopic Methods to Detect Blood Splatter from an Intravascular Catheter with Engineered Sharps Injury Protection". Infection Control & Hospital Epidemiology 34, n. 11 (novembre 2013): 1174–80. http://dx.doi.org/10.1086/673462.

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Objective.To determine whether retractable intravenous devices produced blood splatter and whether blood splatter frequency differed between visual and microscopy detection methods.Methods.In this laboratory-based experiment, 105 venipunctures were performed in a simulated brachial vein containing mock venous blood. The retraction mechanism was activated in a testing chamber with precut fabric filters, placed at 3 different locations, to capture blood splatter. Differences in filter mass, visual inspection, and microscopic analysis for presence of blood on filters were the units of analysis. Descriptive statistics, paired Student t tests, and k statistics were used for data analysis.Results.Blood splatter was detected visually and microscopically as follows: filter A, 70% and 71%, respectively; filter B, 12% and 9%, respectively; and filter C, 13% and 10%, respectively. A statistically significant difference was observed in the mean mass of filter A between before and after activation when confirmed by the naked eye (P = .014) and microscopically (P = .0092). Substantial agreement between methods was observed for filter A (k = 0.78 [95% confidence interval, 0.64-0.92]), filter B (k = 0.73 [95% confidence interval, 0.51-0.95]), and filter C (k = 0.75 [95% confidence interval, 0.55-0.96]). However, blood was detected by microscopy and not by the naked eye in 7 instances (7%).Conclusions.Our findings demonstrate that splatter, which can potentially expose healthcare workers (HCWs) to bloodborne pathogens, is associated with the activation of intravascular catheters with retraction mechanisms. HCWs may not detect this splatter when it occurs and may not report a splash to mucous membranes or nonintact skin. The need to wear personal protective equipment when using such devices is reinforced.

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Qiu, Qian Sheng, Jing Xian Liu, De Qiang Chang, Ning Mao e Xi Sun. "Study of Typical Filter Material on Dust Cleaning". Applied Mechanics and Materials 490-491 (gennaio 2014): 58–63. http://dx.doi.org/10.4028/www.scientific.net/amm.490-491.58.

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filter get peoples attention increasingly as it has become the core of dust bag. In this paper, cleaning process residual resistance and peel rate of dust cleaning cycle were studied. Experimental results show that the initial resistance of the filter were close to the filters, polyester dust filter has a high cleaning strip ratio and a larger interval.

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NIE, SONGLIN, HUI JI, YEQING HUANG, ZHEN HU e YONGPING LI. "ROBUST INTERVAL-BASED MINIMAX-REGRET ANALYSIS METHOD FOR FILTER MANAGEMENT OF FLUID POWER SYSTEM". Asia-Pacific Journal of Operational Research 30, n. 06 (dicembre 2013): 1350021. http://dx.doi.org/10.1142/s0217595913500218.

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Fluid contamination is one of the main reasons for the wear failure and the related downtime in a hydraulic power system. Filters play an important role in controlling the contamination effectively, increasing the reliability of the system, and maintaining the system economically. Due to the uncertainties of system parameters, the complicated relationship among components, as well as the lack of effective approach, managing filters is becoming one of the biggest challenges for engineers and decision makers. In this study, a robust interval-based minimax-regret analysis (RIMA) method is developed for the filter management in a fluid power system (FPS) under uncertainty. The RIMA method can handle the uncertainties existed in contaminant ingressions of the system and contaminant holding capacity of filters without making assumption on probabilistic distributions for random variables. Through analyzing the system cost of all possible filter management alternatives, an interval element regret matrix can be obtained, which enables decision makers to identify the optimal filter management strategy under uncertainty. The results of a case study indicate that the reasonable solutions generated can help decision makers understand the consequence of short-term and long-term decisions, identify optimal strategies for filter allocation and selection with minimized system-maintenance cost and system-failure risk.

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Ozoliņš, O., V. Bobrovs e G. Ivanovs. "DWDM Transmission Based on the Thin-Film Filter Technology". Latvian Journal of Physics and Technical Sciences 48, n. 3 (1 gennaio 2011): 55–65. http://dx.doi.org/10.2478/v10047-011-0021-x.

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DWDM Transmission Based on the Thin-Film Filter Technology A dense wavelength division multiplexing (DWDM) transmission scheme with two thin-film filters (FWHM bandwidth 100 GHz and 200 GHz) has been realized to evaluate the minimum channel interval needed for a satisfactory bit error ratio. For this purpose, detailed research was conducted into the impact of the filters on the optical signal's de-multiplexing in a DWDM system, in which the measurements of eye diagrams and the optical power spectral densities of a received signal were made. From the results of measurements the minimum channel interval has been found for the optical filters that ensures reliable data transmission and higher spectral efficiency of the whole system. It was found that for a DWDM system with a 100 GHz filter a sufficient channel interval is 75 GHz at 10 Gbit/s data transmission speed, which means that its spectral efficiency is increased from 0.1 bit/s/Hz to 0.1333 bit/s/Hz.

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Ausiannikau, A. V., e V. M. Kozel. "Optimal Histogram Filter". Doklady BGUIR 21, n. 5 (25 ottobre 2023): 13–19. http://dx.doi.org/10.35596/1729-7648-2023-21-5-13-19.

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The article discusses a technique for constructing an optimal histogram filter and its modifications, taking into account a priori information about the expected probability distribution density. The main idea of constructing a histogram filter is to apply a special transformation that displays the profile of a section of any distribution law into a constant level of characteristic numbers equivalent to it. This transformation allows to determine the coefficients of the histogram filter. An estimate of the value of the number of data of a particular interval of the histogram is formed by the characteristic function of the filter containing real data and equivalent to the characteristic number. The convergence of the estimates obtained by the histogram filter to the true values of the interval probabilities is shown. Modifications of the optimal histogram filter that require less computational costs for their implementation are considered. The upper bounds of the qualitative characteristics of filters are obtained. It has been established that the optimal histogram filter, regardless of the type of distribution law, provides three times the best quality of identification (recognition) in comparison with the standard histogram estimate. The efficiency of the histogram filter is confirmed by simulations. The histogram filter is an easy-to-implement tool that can be easily integrated into any open distribution law identification (recognition) algorithm.

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Phipps, Mary C., e Peter M. Byron. "A filter for “confidence interval -values”". Computational Statistics & Data Analysis 51, n. 12 (agosto 2007): 6435–46. http://dx.doi.org/10.1016/j.csda.2007.02.015.

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Zahiri, Saeide, Arsham Saeid e Esfandiar Eslami. "A new approach to filters in triangle algebras". Publications de l'Institut Math?matique (Belgrade) 101, n. 115 (2017): 267–83. http://dx.doi.org/10.2298/pim1715267z.

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We develop the filter theory in triangle algebras. We define several interval valued residuated lattice-filters (IVRL-filters for short) in triangle algebras. We investigate the relationships among these types of IVRL-filters. Also, some special triangle algebras are introduced and studied in details.

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Ausiannikau, A. V., e V. M. Kozel. "Filtration of histogram evaluation of probability density based on fuzzy data accessibility to a grouping interval". Doklady BGUIR 19, n. 4 (1 luglio 2021): 13–20. http://dx.doi.org/10.35596/1729-7648-2021-19-4-13-20.

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The paper proposes a histogram estimate of the probability density based on fuzzy data belonging to a grouping interval. A methodology for constructing a histogram estimate using a histogram smoothing filter is presented. The technique of constructing such a filter is described. The main filter parameter is established – the coefficient of the statistical relationship between the amount of data falling into the grouping interval for a single inclusion function and when approaching to use the membership function. The use of an iterative procedure for a histogram filter allows for a greater “smoothness” of the histogram. The simulation results show the effectiveness of using a histogram filter for different data volumes. At the same time, the choice of the number of grouping intervals for the “correct” recognition of probability density becomes not critical. The histogram filter is a simple tool that can easily be built into any algorithm for constructing histogram estimates.

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Liu, Hao, Yong Qing Su, Yan Ming Wang, Ji Guang Yue e Shi Hui Luo. "Internal Model Control Based on Interval Arithmetic for Suspension Systems". Advanced Materials Research 482-484 (febbraio 2012): 2007–11. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.2007.

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This paper deals with the application of interval arithmetic in internal model control (IMC) for suspension systems. The IMC problem is expressed as an optimization of filter parameters. And the optimization can be solved by branch-and-bound scheme with interval arithmetic techniques. We present the algorithm for the model of suspension systems. The effectiveness of the algorithm is demonstrated through simulation results.

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Zahiri, Saeide, Arsham Borumand Saeid e Esfandiar Eslami. "A study of stabilizers in triangle algebras". Mathematica Slovaca 68, n. 1 (23 febbraio 2018): 41–52. http://dx.doi.org/10.1515/ms-2017-0078.

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Abstract In this paper, we introduce the notions of stabilizer of a subset and the stabilizer of a subset with respect to another one in triangle algebras and study them in details. It is shown that the stabilizer of a subset and stabilizer of an interval valued residuated lattice filter (IVRL-filter) with respect to another IVRL-filter are IVRL-filters. We state and prove some theorems which determine some properties of this stabilizers in triangle algebras. Also, we prove that in linearly ordered triangle algebras, stabilizer of a set is an IVRL-extended prime filter. Finally, we consider the influence of stabilizers on product and quotient triangle algebras.

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Hamidizadeh, Ramin, David Liu, Faisal Khosa, John Chung, Darren Klass e Behrang Homayoon. "Retrievable Inferior Vena Cava Filters: A Tertiary Centre Perspective and Quality Assurance Study". Canadian Association of Radiologists Journal 70, n. 2 (maggio 2019): 193–98. http://dx.doi.org/10.1016/j.carj.2018.08.004.

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Purpose To conduct a retrospective review and quality assurance study of inferior vena cava (IVC) filter retrieval over a two-year period at a tertiary care centre. Methods Patients who underwent IVC filter placement or retrieval over a two-year period were identified. Medical records were reviewed for patient characteristics, filter indication, time to filter retrieval, and complications. Results IVC filters were placed in 229 patients between January 1, 2015 and December 31, 2016. 113 retrievals were attempted and 101 filters were successfully retrieved (89.4%). Median time to first retrieval attempt was 48 days (range of 5–728). Seventy-one patients died in the interval after filter insertion before a retrieval attempt at a median time of 27 days (range of 3–430). In 17 patients, retrieval was complicated by or delayed because of penetration of IVC wall (n = 6), large thrombus burden trapped by filter (n = 5), filter tilt or migration (n = 3), and unclear reasons (n = 3). Time-to-first unsuccessful retrieval attempt was 141 days (median). Of all filters placed, 55.9% were never retrieved. Excluding deceased patients with in-situ filters (n = 71) and unsuccessful retrievals left in-situ as permanent filters (n = 5), there remains 52 patients (33%), with a median filter in-situ time of 488 days. Conclusion Our study indicates that as many as 33% of patients may have been lost to follow-up of their in-situ IVC filter. Considering widespread reports of long-term complications and the recent safety alert issued by Health Canada, it is evident that a unified strategy is needed to track patients post filter insertion.

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Degtyarev, Andrey N., Igor L. Afonin e Alexander L. Polyakov. "Physically realizable reconstruction of a continuous signal after sampling". Radioelectronics. Nanosystems. Information Technologies. 16, n. 1 (14 marzo 2024): 3–10. http://dx.doi.org/10.17725/j.rensit.2023.16.003.

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It is proposed to describe signals in a physically realizable basis. Correlation functions of impulse characteristics of physically implemented filters are used as basic functions. To obtain analytical expressions of the functions of the proposed physically realizable basis, it is proposed to use inverse Fourier transforms from approximations (Butterworth, Chebyshev, etc.) of the squares of the amplitude-frequency characteristics of normalized low-pass filters. The basis, functions are copies of the indicated correlation functions of the impulse characteristics, shifted relative to each other by the same time interval, which is the sampling interval. It is shown that there is a sampling theorem in the space of the introduced functions. The exact restoration of the signal is possible if the functions of the considered basis have the property of readability. In this case, the considered basic functions are functions of counts and are not physically implemented. To reduce the error of restoring a continuous signal from its readings using the proposed basis, it is necessary to increase the order of the filter, the pulse characteristics of which are used in the formation of the basis. To restore a continuous signal, its samples must be fed to two cascaded filters. The first filter must have an impulse response, the correlation function of which is used to form a physically realizable basis. The second filter must be matched to the impulse response of the first filter.

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Jiang, Chen, Shu-bi Zhang e Qiu-zhao Zhang. "A Novel Robust Interval Kalman Filter Algorithm for GPS/INS Integrated Navigation". Journal of Sensors 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/3727241.

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Kalman filter is widely applied in data fusion of dynamic systems under the assumption that the system and measurement noises are Gaussian distributed. In literature, the interval Kalman filter was proposed aiming at controlling the influences of the system model uncertainties. The robust Kalman filter has also been proposed to control the effects of outliers. In this paper, a new interval Kalman filter algorithm is proposed by integrating the robust estimation and the interval Kalman filter in which the system noise and the observation noise terms are considered simultaneously. The noise data reduction and the robust estimation methods are both introduced into the proposed interval Kalman filter algorithm. The new algorithm is equal to the standard Kalman filter in terms of computation, but superior for managing with outliers. The advantage of the proposed algorithm is demonstrated experimentally using the integrated navigation of Global Positioning System (GPS) and the Inertial Navigation System (INS).

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Nie, S. L., Y. P. Li, X. Y. Shi, G. H. Huang e B. Hu. "An IPINP model for the assessment of filter allocation and replacement strategies in a hydraulic contamination control system under uncertainty". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, n. 4 (11 dicembre 2008): 999–1015. http://dx.doi.org/10.1243/09544062jmes1074.

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An interval-parameter integer non-linear programming (IPINP) model is developed for the assessment of filter allocation and replacement strategies in a hydraulic contamination control system under uncertainty. The IPINP can handle uncertainties expressed as interval values that exist in the left- and right-hand sides of constraints as well as in the objective function. A piecewise linearization approach is proposed to solve the IPINP model, which has advantages in identifying global optimum and is associated with low computational efforts for an uncertain non-linear programme. The developed method has been applied to a case of planning filter allocation and replacement strategies under uncertainty for a fluid power system (FPS) with a single circuit. Three different contaminant ingression/generation rates are examined based on several filter-installation scenarios. The combination of low-costing suction and return filters exhibits excellent contaminant resistibility along with the optimum replacement periods of filter elements and operation costs under the low and medium contaminant ingression/generation level. The solutions can be used for generating a range of decision alternatives and thus help the decision-makers to identify desired filter allocation and replacement plan with a minimized operation cost and a minimized system-failure risk for FPS.

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Li, Linmin, Peng Lin e Junfeng Zhang. "Event-Triggered Asynchronous Filter of Positive Switched Systems with State Saturation". Mathematical Problems in Engineering 2022 (21 giugno 2022): 1–24. http://dx.doi.org/10.1155/2022/7276646.

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This paper investigates the event-triggered asynchronous filter of positive switched systems with state saturation using linear programming and multiple Lyapunov functions. First, a filter is constructed for continuous-time positive switched systems. Under the asynchronous switching law, an error system is proposed with respect to positive switched systems and their filters, where the state saturation term is described in a polytopic form by virtue of the saturation property. A novel event-triggering condition is addressed based on a 1-norm inequality. Under the event-triggering condition, the error system is transformed into an interval system with lower and upper bounds. By using multiple Lyapunov functions and linear programming, the positivity and stability of the error system are achieved by considering the corresponding properties of the lower and upper bounds, respectively. Then, the event-triggered l1-gain filter and nonfragile filter are also proposed for the systems with disturbances. Moreover, the presented filter framework is extended to the discrete-time case. Finally, two examples are given to verify the effectiveness of the proposed filters.

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Bae, Tae-Wuk, Kee-Koo Kwon e Kyu-Hyung Kim. "Electrocardiogram Fiducial Point Detector Using a Bilateral Filter and Symmetrical Point-Filter Structure". International Journal of Environmental Research and Public Health 18, n. 20 (14 ottobre 2021): 10792. http://dx.doi.org/10.3390/ijerph182010792.

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The characteristics or aspects of important fiducial points (FPs) in the electrocardiogram (ECG) signal are complicated because of various factors, such as non-stationary effects and low signal-to-noise ratio. Due to the various noises caused by the ECG signal measurement environment and by typical ECG signal deformation due to heart diseases, detecting such FPs becomes a challenging task. In this study, we introduce a novel PQRST complex detector using a one-dimensional bilateral filter (1DBF) and the temporal characteristics of FPs. The 1DBF with noise suppression and edge preservation preserves the P- or T-wave whereas it suppresses the QRS-interval. The 1DBF acts as a background predictor for predicting the background corresponding to the P- and T-waves and the remaining flat interval excluding the QRS-interval. The R-peak and QRS-interval are founded by the difference of the original ECG signal and the predicted background signal. Then, the Q- and S-points and the FPs related to the P- and T-wave are sequentially detected using the determined searching range and detection order based on the detected R-peak. The detection performance of the proposed method is analyzed through the MIT-BIH database (MIT-DB) and the QT database (QT-DB).

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Schudel, Paul, e Markus Boller. "Onsite Wastewater Treatment with Intermittent Buried Filters". Water Science and Technology 22, n. 3-4 (1 marzo 1990): 93–100. http://dx.doi.org/10.2166/wst.1990.0188.

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A few intermittent buried sand filters have been constructed in Switzerland for the onsite treatment of small wastewater sources. The good experiences to date will certainly favour a more frequent application in the future. Investigations of the hydraulic behaviour and the removal efficiency, especially in one filter during and after a hydraulic flush, showed that the hydraulic load per dosing interval should preferably not be larger than 10 1/m2,interval. Tracer experiments as well as the analysis of pollutants during the intervals revealed considerable quality fluctuations along the hydraulic peak discharge depending strongly on the instantaneous hydraulic dose. Furthermore, maturation periods of several months are necessary in order to reach a maximum steady state performance that usually includes full nitrification. Besides detailed information on the hydraulic behaviour, a series of performance data of different buried filters gives an overview of the concentrations and the removal rates observed for organic matter and nitrogen compounds.

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Freid, Aaron P., Paul K. Johnson, Manuela Musella, Reto Mu¨ller, Julie E. Steinbrenner e Robert D. Palumbo. "Solar Blind Pyrometer Temperature Measurements in High Temperature Solar Thermal Reactors: A Method for Correcting the System-Sensor Cavity Reflection Error". Journal of Solar Energy Engineering 127, n. 1 (1 febbraio 2005): 86–93. http://dx.doi.org/10.1115/1.1796992.

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We developed a method that enables one to correct solar blind pyrometer cavity temperature measurements for the system-sensor reflection error. The method is valid for measurements made on diffusely emitting and reflecting cavity surfaces when there is no participating medium between the pyrometer and the surface of interest. The surfaces’ emissivities must be known. The procedure gives the uncertainty interval associated with the correction. The procedure was validated by measuring surface temperatures in a solar reactor insulated with Yttria-stabilized Zirconia felt receiving concentrated solar radiation. The temperature range of the experimental study was from 1100–1600 K. Temperature measurements made with a pyrometer having a narrow band filter centered at 1.398 μm were compared to temperatures measured with Zirconia felt shielded thermocouples. Uncorrected pyrometer measurements differed from the thermocouple measurements by as much as 350 K. The thermocouple measurements mostly fell within the system-sensor uncertainty interval of the corrected temperature measurements. The uncertainty interval depends both on the number of surfaces probed with the pyrometer and the nature of the solar blind filter. A numerical simulation study showed that a UV filter centered at a wavelength near 0.285 μm gives tighter system-sensor uncertainty intervals than an IR filter centered at 1.398 μm.

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Lee, Chang-Kyu, Chansoo Park, June-Seok Choi e Jong-Oh Kim. "Effects of various chemical cleaning conditions for pressured MF process". Water Science and Technology 75, n. 5 (21 dicembre 2016): 1063–70. http://dx.doi.org/10.2166/wst.2016.573.

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A pilot-scale pressured hollow-fiber microfiltration (MF) process as pretreatment for the reverse osmosis process was studied and operated under various conditions to assess the relative influence of backwashing, chemical enhanced backwashing (CEB), and bag filter application. The pilot plant process consisted of backwashing but without the CEB or the bag filter as the first step of the research. As the second step of the research, the impact of the backwashing on permeability recovery was assessed at different intervals followed by the influence of CEB on flowrate recovery. Results from operating the pilot-scale hollow-fiber membrane modules for more than 1 year have demonstrated that the appropriate pore size of bag filters was 25–50 μm and the optimized backwashing process was every 30 minutes with 25 mg/L of NaOCl, and CEB with an interval of 10 cycles with the use of 100 mg/L NaOCl.

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Bocquet, M. "Ensemble Kalman filtering without the intrinsic need for inflation". Nonlinear Processes in Geophysics 18, n. 5 (20 ottobre 2011): 735–50. http://dx.doi.org/10.5194/npg-18-735-2011.

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Abstract. The main intrinsic source of error in the ensemble Kalman filter (EnKF) is sampling error. External sources of error, such as model error or deviations from Gaussianity, depend on the dynamical properties of the model. Sampling errors can lead to instability of the filter which, as a consequence, often requires inflation and localization. The goal of this article is to derive an ensemble Kalman filter which is less sensitive to sampling errors. A prior probability density function conditional on the forecast ensemble is derived using Bayesian principles. Even though this prior is built upon the assumption that the ensemble is Gaussian-distributed, it is different from the Gaussian probability density function defined by the empirical mean and the empirical error covariance matrix of the ensemble, which is implicitly used in traditional EnKFs. This new prior generates a new class of ensemble Kalman filters, called finite-size ensemble Kalman filter (EnKF-N). One deterministic variant, the finite-size ensemble transform Kalman filter (ETKF-N), is derived. It is tested on the Lorenz '63 and Lorenz '95 models. In this context, ETKF-N is shown to be stable without inflation for ensemble size greater than the model unstable subspace dimension, at the same numerical cost as the ensemble transform Kalman filter (ETKF). One variant of ETKF-N seems to systematically outperform the ETKF with optimally tuned inflation. However it is shown that ETKF-N does not account for all sampling errors, and necessitates localization like any EnKF, whenever the ensemble size is too small. In order to explore the need for inflation in this small ensemble size regime, a local version of the new class of filters is defined (LETKF-N) and tested on the Lorenz '95 toy model. Whatever the size of the ensemble, the filter is stable. Its performance without inflation is slightly inferior to that of LETKF with optimally tuned inflation for small interval between updates, and superior to LETKF with optimally tuned inflation for large time interval between updates.

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Guetman, F. I., I. S. Kim, A. Bücher, C. A. Druzhinin, J. C. Noëns, R. T. Salakhutdinov, A. A. Semenikin e V. I. Skomorovsky. "On Filter Observations of Coronal Structures in the Light of FeX 6374 Å Emission Line". International Astronomical Union Colloquium 144 (1994): 575–78. http://dx.doi.org/10.1017/s0252921100026075.

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AbstractThe red coronal line of Fe X (6374 Å) seems to be extremely suitable for filter observations due to reduced sky scattering in this spectral interval and absence of blending by Fraunhofer lines. Comparative analysis of location of Hαstructures in colour and black-white pictures of the solar corona of July 11, 1991 was carried out. A conclusion was made that care should be taken when interference filters are used for the red corona observations. Non-ideal monochromatization of present-day existing interference filters may be responsible for some ”false“ red and white coronal structures which belong to Hαprominence emission. Estimations of parameters of an interference filter for the reliable red coronal observations are presented.

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Panek, P. "Time-Interval Measurement Based on SAW Filter Excitation". IEEE Transactions on Instrumentation and Measurement 57, n. 11 (novembre 2008): 2582–88. http://dx.doi.org/10.1109/tim.2008.925014.

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Zhang, Jian, e Ling Shen. "Applied Technology in an Adaptive Particle Filter Based on Interval Estimation and KLD-Resampling". Advanced Materials Research 1014 (luglio 2014): 452–58. http://dx.doi.org/10.4028/www.scientific.net/amr.1014.452.

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Particle filter as a sequential Monte Carlo method is widely applied in stochastic sampling for state estimation in a recursive Bayesian filtering framework. The efficiency and accuracy of the particle filter depends on the number of particles and the relocating method. The automatic selection of sample size for a given task is therefore essential for reducing unnecessary computation and for optimal performance, especially when the posterior distribution greatly varies overtime. This paper presents an adaptive resampling method (IE_KLD_PF) based on interval estimation, and after interval estimating the expectation of the system states, the new algorithm adopts Kullback-Leibler distance (KLD) to determine the number of particles to resample from the interval and update the filter results by current observation information. Simulations are performed to show that the proposed filter can reduce the average number of samples significantly compared to the fixed sample size particle filter.

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Usman, Hamisu, e Nuraddeen Magaji. "Interval Type - 2 Fuzzy Logic Controller Based Shunt Active Power Filter for Power Quality Enhencement". International Journal of Engineering and Advanced Technology 13, n. 1 (30 ottobre 2023): 68–73. http://dx.doi.org/10.35940/ijeat.a4299.1013123.

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Frequent wide spread of power electronics equipment to consumers have led to power quality problem in power system network, as a result to their nonlinear in nature. Due to this problem, current and voltage wave forms are no longer sinusoidal, which resulted in harmonics on them. Various methods have been deployed in order to mitigate the harmonic issues, like passive power filters and shunt active power filters. Presently, passive power filters are limited in used, because of its demerits as it produced parallel resonances, heavy in size and mitigate few harmonics. With the advancement in technology, shunt active power filters have become superior to passive power filters due to its limitations. Shunt active power filters was tested for suppressing harmonics produced by nonlinear loads. This article, used synchronous reference frame (SRF) in generating harmonic produced by nonlinear loads. However, T2FLC is utilized in controlling the DC bus voltage of the filter constant. Hysteresis current controller was introduced for firing the gating signal of the IGBT inverter circuit. MATLAB software was deployed in the simulation work. Results obtained have satisfied the tolerable 2014 revised harmonics limit.

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Faybusovich, L., e T. Mouktonglang. "Deterministic Kalman Filtering on Semi-Infinite Interval". International Journal of Mathematics and Mathematical Sciences 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/490139.

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35

Noumen, Euclide, Fabrice Tchoua Yinga, Blaise Blériot Koguep Njionou e Chris Cornelis. "An Exploration of Ideals and Filters in Triangle Algebras". Axioms 13, n. 8 (21 agosto 2024): 566. http://dx.doi.org/10.3390/axioms13080566.

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In the study of algebraic structures related to logical systems, ideals and filters have different meanings and are algebraic notions related to logical provable formulas. Unlike the classical Boolean lattice theory, ideals and filters are not dual notions in residuated lattices. An interesting subclass of residuated lattices is the class of triangle algebras, which is an equational representation of interval-valued residuated lattices that provides an algebraic framework for using closed intervals as truth values in fuzzy logic. The main aim of this article is to introduce and study the concept of ideals in triangle algebras and investigate the connection between ideals and filters. We first point out that the construction procedure for the filter generated by a subset of a triangle algebra established by another study is incorrect, and we proceed to give an alternative characterization.

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Lu, Zhongda, Guoliang Zhang, Yi Sun, Jie Sun, Fangming Jin e Fengxia Xu. "Nonfragile H∞ Filter Design for Nonlinear Continuous-Time System with Interval Time-Varying Delay". Journal of Control Science and Engineering 2018 (5 settembre 2018): 1–17. http://dx.doi.org/10.1155/2018/8198603.

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This paper investigates nonfragile H∞ filter design for a class of continuous-time delayed Takagi-Sugeno (T-S) fuzzy systems with interval time-varying delays. Filter parameters occur multiplicative gain variations according to the filter’s implementation, to handle this variations, a nonfragile H∞ filter is presented and a novel filtering error system is established. The nonfragile H∞ filter guarantees the filtering error system to be asymptotically stable and satisfies given H∞ performance index. By constructing a novel Lyapunov-Krasovskii function and using the linear matrix inequality (LMI), delay-dependent conditions are exploited to derive sufficient conditions for nonfragile designing H∞ filter. Using new matrix decoupling method to reduce the computational complexity, the filter parameters can be obtained by solving a set of linear matrix inequalities (LMIs). Finally, numerical examples are given to show the effectiveness of the proposed method.

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Du, Hao Cui, Bin Sun e Ying Le Yao. "Research of Unary Lattice Implication Algebra Equations on Interval Sets". Advanced Materials Research 850-851 (dicembre 2013): 761–66. http://dx.doi.org/10.4028/www.scientific.net/amr.850-851.761.

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The concepts are re-defined on the interval sets which are filter, prime filter, LI-ideal, dual atom and convex sub-lattice in the lattice implication algebra. Three basic unary lattice implication algebra equations on the interval sets are researched. The necessary and sufficient conditions for existence of solutions for the equations are presented. And some properties of equation sets also are given.

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Zigic, Aleksandar. "Preset time count rate meter using adaptive digital signal processing". Nuclear Technology and Radiation Protection 20, n. 1 (2005): 64–73. http://dx.doi.org/10.2298/ntrp0501064z.

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Two presented methods were developed to improve classical preset time count rate meters by using adapt able signal processing tools. An optimized detection algorithm that senses the change of mean count rate was implemented in both methods. Three low-pass filters of various structures with adaptable parameters to implement the control of the mean count rate error by suppressing the fluctuations in a controllable way, were considered and one of them implemented in both methods. An adaptation algorithm for preset time interval calculation executed after the low-pass filter was devised and implemented in the first method. This adaptation algorithm makes it possible to obtain shorter preset time intervals for higher stationary mean count rate. The adaptation algorithm for preset time interval calculation executed before the low-pass filter was devised and implemented in the second method. That adaptation algorithm enables sensing of a rapid change of the mean count rate before fluctuations suppression is carried out. Some parameters were fixed to their optimum values after appropriate optimization procedure. Low-pass filters have variable number of stationary coefficients depending on the specified error and the mean count rate. They implement control of the mean count rate error by suppressing fluctuations in a controllable way. The simulated and realized methods, using the developed algorithms, guarantee that the response time shall not exceed 2 s for the mean count rate higher than 2 s-1 and that controllable mean count rate error shall be within the range of ?4% to ?10%.

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Ashokaraj, Immanuel, Antonios Tsourdos, Peter Silson e Brian White. "SENSOR BASED ROBOT LOCALISATION AND NAVIGATION: USING INTERVAL ANALYSIS AND NONLINEAR KALMAN FILTERS." Transactions of the Canadian Society for Mechanical Engineering 29, n. 2 (giugno 2005): 211–27. http://dx.doi.org/10.1139/tcsme-2005-0014.

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Multiple sensor fusion for robot localisation and navigation has attracted a lot of interest in recent years. This paper describes a sensor based navigation and localisation approach for an autonomous mobile robot using an interval analysis (IA) based adaptive mechanism for the non-linear Kalman filter namely the Extended Kalman filter (EKF). The map used for this study is two-dimensional and assumed to be known a priori. The robot is equipped with inertial sensors (INS), encoders and ultrasonic sensors. A non-linear Kalman filter is used to estimate the robots position using the inertial sensors and encoders. The ultrasonic sensors use an Interval Analysis (IA) algorithm for guaranteed robot localisation. Since the Kalman Filter estimates may be affected by bias, drift etc. we propose an adaptive mechanism using IA to correct these defects in estimates. In the presence of landmarks the complementary interval robot position information from the IA algorithm with uniform distribution using ultrasonic sensors is used to estimate and bound the errors in the non-linear Kalman filter robot position estimate with a Gaussian distribution.

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Dutta, Gopa, Palla Vinay Kumar e Salauddin Mohammad. "Retrieving characteristics of inertia gravity wave parameters with least uncertainties using the hodograph method". Atmospheric Chemistry and Physics 17, n. 23 (12 dicembre 2017): 14811–19. http://dx.doi.org/10.5194/acp-17-14811-2017.

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Abstract. We have analyzed wind velocities measured with high-resolution Global Positioning System (GPS) radiosondes which have been flown continuously from Hyderabad for 120 h with an interval of 6 h. Hodograph method has been used to retrieve inertia gravity waves (IGWs) parameters. Background winds are removed from the time series by detrending, whereas polynomials of different orders are removed to obtain the fluctuations from individual profiles. A Butterworth filter is used to extract the monochromatic IGW component. Another filter finite impulse response (FIR1) is tried in a similar manner to test the effects of filters in estimating IGW characteristics. Results reveal that the fluctuation profiles differ with the change in polynomial orders, but the IGW parameters remain same when a Butterworth filter is chosen to extract the monochromatic wave component. The FIR1 filter produces results with a broader range. The direction of wave propagation can be confirmed with additional temperature information.

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Borzooei, Rajab Ali, Hee Sik Kim, Young Bae Jun e Sun Shin Ahn. "MBJ-neutrosophic subalgebras and filters in $ BE $-algebras". AIMS Mathematics 7, n. 4 (2022): 6016–33. http://dx.doi.org/10.3934/math.2022335.

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<abstract><p>The concept of a neutrosophic set, which is a generalization of an intuitionistic fuzzy set and a para consistent set etc., was introduced by F. Smarandache. Since then, it has been studied in various applications. In considering a generalization of the neutrosophic set, Mohseni Takallo et al. used the interval valued fuzzy set as the indeterminate membership function because interval valued fuzzy set is a generalization of a fuzzy set, and introduced the notion of MBJ-neutrosophic sets, and then they applied it to BCK/BCI-algebras. The aim of this paper is to apply the concept of MBJ-neutrosophic sets to a $ BE $-algebra, which is a generalization of a BCK-algebra. The notions of MBJ-neutrosophic subalgebras and MBJ-neutrosophic filters of $ BE $-algebras are introduced and related properties are investigated. The conditions under which the MBJ-neutrosophic set can be a MBJ-neutrosophic subalgebra/filter are searched. Characterizations of MBJ-neutrosophic subalgebras and MBJ-neutrosophic filters are considered. The relationship between an MBJ-neutrosophic subalgebra and an MBJ-neutrosophic filter is established.</p></abstract>

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Wang, Wenli, e Philip Winters. "Statistically Significant Efficiency Testing of HEPA Filters". Journal of the IEST 47, n. 1 (14 settembre 2004): 101–6. http://dx.doi.org/10.17764/jiet.47.1.bq380t6134311822.

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High Efficiency Particulate Air (HEPA) filter manufacturers must ensure the accuracy of efficiency testing for these filters and, at the same time, keep productivity at a reasonable level. This study describes tests conducted to determine the minimum time required to provide statistically significant efficiencies of HEPA filters using a test system currently in use of HEPA filter production. The test results of over 300 HEPA filters were analyzed in this study. The approaches in IEST RP-CC-007.1: Testing ULPA Filters for statistical analysis of particle counts were followed. A Poisson distribution was used to describe the variations and to calculate the lower and upper limits of measured counts at 95% confidence level. This study shows that 90 seconds is sufficient for this test system to determine whether a HEPA filter has an efficiency of 99.990% or higher at 95% confidence. Longer tests will cause the mean measured efficiency to approach the filter's true efficiency and also narrow the confidence interval. However, challenging HEPA filters made of glass fiber media with oil aerosols for up to one hour does not significantly change the filter's true efficiency performance. The preferred approach for a new test system is to use software that calculates the confidence limits of filter efficiency after each sampling cycle and determines whether to continue testing. For an existing system without this type of program (such as the one evaluated in this study), analysis is necessary to make sure the HEPA filters are challenged with enough aerosol particles.

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He, Shuping. "Resilient - Filtering of Uncertain Markovian Jumping Systems within the Finite-Time Interval". Abstract and Applied Analysis 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/791296.

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This paper studies the resilient - filtering problem for a class of uncertain Markovian jumping systems within the finite-time interval. The objective is to design such a resilient filter that the finite-time - gain from the unknown input to an estimation error is minimized or guaranteed to be less than or equal to a prescribed value. Based on the selected Lyapunov-Krasovskii functional, sufficient conditions are obtained for the existence of the desired resilient - filter which also guarantees the stochastic finite-time boundedness of the filtering error dynamic systems. In terms of linear matrix inequalities (LMIs) techniques, the sufficient condition on the existence of finite-time resilient - filter is presented and proved. The filter matrices can be solved directly by using the existing LMIs optimization techniques. A numerical example is given at last to illustrate the effectiveness of the proposed approach.

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Qiang, Xingzi, Rui Xue e Yanbo Zhu. "Two-Dimensional Monte Carlo Filter for a Non-Gaussian Environment". Electronics 10, n. 12 (9 giugno 2021): 1385. http://dx.doi.org/10.3390/electronics10121385.

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In a non-Gaussian environment, the accuracy of a Kalman filter might be reduced. In this paper, a two- dimensional Monte Carlo Filter is proposed to overcome the challenge of the non-Gaussian environment for filtering. The two-dimensional Monte Carlo (TMC) method is first proposed to improve the efficacy of the sampling. Then, the TMC filter (TMCF) algorithm is proposed to solve the non-Gaussian filter problem based on the TMC. In the TMCF, particles are deployed in the confidence interval uniformly in terms of the sampling interval, and their weights are calculated based on Bayesian inference. Then, the posterior distribution is described more accurately with less particles and their weights. Different from the PF, the TMCF completes the transfer of the distribution using a series of calculations of weights and uses particles to occupy the state space in the confidence interval. Numerical simulations demonstrated that, the accuracy of the TMCF approximates the Kalman filter (KF) (the error is about 10−6) in a two-dimensional linear/ Gaussian environment. In a two-dimensional linear/non-Gaussian system, the accuracy of the TMCF is improved by 0.01, and the computation time reduced to 0.067 s from 0.20 s, compared with the particle filter.

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Trung Tran, Thien, Haraldur Bjarnason, Jennifer McDonald, Nils Oddvar Skaga, Damon E. Houghton, Brian Kim, Knut Stavem e Nils Einar Kløw. "Prophylactic placement of inferior vena cava filters and the risk of death or venous thromboembolism in severe trauma patients: a retrospective study comparing two hospitals with different approaches". Acta Radiologica Open 10, n. 3 (marzo 2021): 205846012199934. http://dx.doi.org/10.1177/2058460121999345.

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Background Prophylactic use of inferior vena cava filters to prevent pulmonary embolism in trauma is controversial. The practice varies between hospitals and countries, in part due to conflicting evidence and guidelines. Purpose To compare the effects of pulmonary embolism, deep venous thrombosis and mortality in two hospitals using prophylactic inferior vena cava filter placement or prophylactic anticoagulation alone. Material and Methods Patients presenting with severe trauma were recruited from two level-1 trauma centres between January 2008 and December 2013. Recruited patients from an US hospital having prophylactic inferior vena cava filter inserted were compared to a Scandinavian hospital using prophylactic anticoagulation alone. Inclusion criteria were age >15 years, Injury Severity Score >15 and survival >24 h after hospital admission. Patients with venous thromboembolism diagnosed prior to inferior vena cava filter placement were excluded. A Cox proportional hazard regression model was used with adjustment for immortal time bias and predictor variables. Results In total, 951 patients were reviewed, 282 from an US hospital having inferior vena cava filters placed and 669 from a Scandinavian hospital without inferior vena cava filters. The mean age was 45.9 vs. 47.4 years and the mean Injury Severity Score was 29.8 vs. 25.9, respectively. Inferior vena cava filter placement was not associated with the hazard of pulmonary embolism (Hazard ratio=0.43; 95% confidence interval (CI) 0.12, 1.45; P=0.17) or mortality (Hazard ratio=1.16; 95% CI 0.70, 1.95; P=0.56). However, an increased rate of deep venous thrombosis was observed with inferior vena cava filters in place (Hazard ratio=3.75; 95% CI 1.68, 8.36; P=0.001). Conclusion In severely injured trauma patients, prophylactic inferior vena cava filter placement was not associated with pulmonary embolism or mortality. However, inferior vena cava filters were associated with increased rate of deep venous thrombosis.

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Haslett, Stephen. "COVARIANCES FOR FIXED INTERVAL SMOOTHED KALMAN FILTER PARAMETER ESTIMATES". Australian Journal of Statistics 32, n. 2 (giugno 1990): 205–16. http://dx.doi.org/10.1111/j.1467-842x.1990.tb01013.x.

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Yang, Yanting, Yan Liang, Linfeng Xu, Yanbo Yang e Yuemei Qin. "Upper bound filter under interval constraints and multiplicative noises". IET Control Theory & Applications 13, n. 15 (15 ottobre 2019): 2482–91. http://dx.doi.org/10.1049/iet-cta.2019.0253.

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Tran, Tuan Anh, Carine Jauberthie, Françoise Le Gall e Louise Travé-Massuyès. "Interval Kalman filter enhanced by positive definite upper bounds". IFAC-PapersOnLine 50, n. 1 (luglio 2017): 1595–600. http://dx.doi.org/10.1016/j.ifacol.2017.08.315.

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Burbeck, Christina A., e Yen Lee Yap. "Spatial-filter selection in large-scale spatial-interval discrimination". Vision Research 30, n. 2 (gennaio 1990): 263–72. http://dx.doi.org/10.1016/0042-6989(90)90042-j.

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van de Wetering, J., R. G. Westendorp, J. G. van der Hoeven, B. Stolk, J. D. Feuth e P. C. Chang. "Heparin use in continuous renal replacement procedures: the struggle between filter coagulation and patient hemorrhage." Journal of the American Society of Nephrology 7, n. 1 (gennaio 1996): 145–50. http://dx.doi.org/10.1681/asn.v71145.

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Abstract (sommario):

Heparin is the most widely used anticoagulant in continuous renal replacement procedures but little is known about the balance between filter coagulation and patient hemorrhage during treatment. Filter survival and hemorrhagic complications during 240 filter periods in 78 critically ill patients, treated with continuous arteriovenous hemofiltration and hemodiafiltration, were studied for this article. The crude incidence of filter coagulation was 17.7 +/- 2.5 (mean +/- SE) per 1000 h at an activated partial thromboplastin time (APTT) of 15 to 35 s, as determined in systemic blood samples. The incidence of filter coagulation gradually decreased to 9.0 +/- 2.7 per 1000 h at an APTT of 45 to 55 s (P = 0.031). The crude incidence of patient hemorrhage was 2.9 +/- 1.0 per 1000 h at an APTT of 15 to 35 s and increased almost threefold to 7.4 +/- 2.4 per 1000 h when the APTT was 45 to 55 s (P = 0.009). There was no difference in filter survival between treatment with hemofiltration only and hemodiafiltration. Mean survival of acrylonitrile filters (33.8 +/- 4.3) was significantly lower compared with the survival of polyamide filters (104.1 +/- 14.4 h, P = 0.003). After adjustment for the type of the filter, mean arterial blood pressure, and platelet count, the risk for filter coagulation decreased 25% (relative risk, 0.77; 95% confidence interval [CI], 0.62 to 0.96) for every 10-s increase in APTT. At the same time, the risk for patient hemorrhage increased 50% (relative risk, 1.57; 95% CI, 1.43 to 1.72). The occurrence of filter coagulation or hemorrhages were not correlated with the administered dose of heparin. Concurrent use of coumarin derivatives had a positive effect on filter survival, without increasing the overall incidence of hemorrhages. It was concluded that the systemic APTT is a good predictor of the risk for filter coagulation and patient hemorrhage. Safety and efficacy of heparin therapy seems optimal at an APTT between 35 and 45 s.

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