Window Threshold Research Articles

Artificial Neural Network-Based Data Recovery System for the Time Series of Tide Stations

ABSTRACT Lee, J.-W. and Park, S.-C., 2016. Artificial neural network-based data recovery system for the time series of tide stations. Accurate prediction of missing water levels attributable to reasons ranging from recording failure and transmission problems to mistakes made by field staff is essential in coastal and oceanic areas. This paper presents a new system for data recovery based on the artificial neural network soft-computing technique and an end-point fixing method. Only the past time series of tide stations are used, therefore, the data recovery system is not only simple and fast but also effective in situations where all the neighboring tide stations simultaneously malfunction. To verify the efficacy of the proposed data recovery system, we utilized the system at the tide stations located in the eastern part of Korea. Further, we calibrated parameters such as window size and thresholds and conducted performance tests in terms of statistical parameter. Our results indicate that although the per...

Sequential monitoring of SCADA systems against cyber/physical attacks

The sequential monitoring of SCADA systems against cyber/physical attacks is considered in this paper. The SCADA systems are described by the discrete-time state space models in the presence of random noises. The cyber/physical attacks are modeled as additive signals of short duration impacted both the state evolution and the sensor measurement equations. The detection of attacks is formulated as the problem of sequential transient change detection in stochastic-dynamical systems. The steady-state Kalman filter and the fixed-size parity space are utilized for generating the sequence of residuals. The unified statistical model is developed to describe the residual generation by both methods. Based on this statistical model, the Variable Threshold Window Limited CUmulative SUM (VTWL CUSUM) algorithm is designed to detect the transient changes. Taking into consideration the detection criterion, which aims at minimizing the worst-case probability of missed detection subject to a given value on the worst-case probability of false alarm, the thresholds are tuned for optimizing the VTWL CUSUM algorithm. It is shown that the optimal choice of thresholds leads to the simple Finite Moving Average (FMA) detection rule. The proposed algorithms are applied to detect the covert attack on a simple SCADA water distribution network.

基于时间窗口阈值法的山丹县农作物种植结构变化

及时准确地获取区域农作物种植结构信息，对于保障区域农业可持续发展及国家粮食安全都具有重要意义。本文以黑河流域山丹县为研究区，基于TM/ETM+影像，利用时间窗口阈值法对山丹县2007和2012年大麦、小麦、油菜和玉米的空间分布进行遥感识别，并分析其变化。结果表明：1) 山丹县农作物种植结构提取总体精度87.20%，Kappa系数0.84。2) 2007~2012年，山丹县大麦的种植面积和种植比例呈下降趋势，小麦、油菜和玉米的种植面积和种植比例呈增加趋势，其他农作物的种植面积小幅增加但种植比例下降，增加的小麦、油菜和玉米主要由其他农作物转移而来。 Timely and accurately obtaining crop planting structure is crucial for guaranteeing the agriculture sustainable development and national food security. Taking Shandan County in the Heihe River Basin as the study area, we adopted a time window threshold method based on TM/ETM+ image to extract the spatial distribution of barley, wheat, rapeseed and corn of Shandan County in 2007 and 2012. The changes in the crop planting structure and the driving forces behind them were also analyzed. The results show that: 1) the overall accuracy of crop planting structure extraction was 87.20%, with Kappa coefficient of 0.84; 2) the planting area and proportion of barley decreased during 2007-2012, while those of wheat, rapeseed and corn increased. The planting area of other crops slightly increased while the planting proportion of it slightly decreased. The increased wheat, rapeseed and corn were mainly converted from other crops.

Modelling the regulatory system for diabetes mellitus with a threshold window

Piecewise (or non-smooth) glucose–insulin models with threshold windows for type 1 and type 2 diabetes mellitus are proposed and analyzed with a view to improving understanding of the glucose–insulin regulatory system. For glucose–insulin models with a single threshold, the existence and stability of regular, virtual, pseudo-equilibria and tangent points are addressed. Then the relations between regular equilibria and a pseudo-equilibrium are studied. Furthermore, the sufficient and necessary conditions for the global stability of regular equilibria and the pseudo-equilibrium are provided by using qualitative analysis techniques of non-smooth Filippov dynamic systems. Sliding bifurcations related to boundary node bifurcations were investigated with theoretical and numerical techniques, and insulin clinical therapies are discussed. For glucose–insulin models with a threshold window, the effects of glucose thresholds or the widths of threshold windows on the durations of insulin therapy and glucose infusion were addressed. The duration of the effects of an insulin injection is sensitive to the variation of thresholds. Our results indicate that blood glucose level can be maintained within a normal range using piecewise glucose–insulin models with a single threshold or a threshold window. Moreover, our findings suggest that it is critical to individualise insulin therapy for each patient separately, based on initial blood glucose levels.

Directional deep brain stimulation: an intraoperative double-blind pilot study.

Deep brain stimulation of different targets has been shown to drastically improve symptoms of a variety of neurological conditions. However, the occurrence of disabling side effects may limit the ability to deliver adequate amounts of current necessary to reach the maximal benefit. Computed models have suggested that reduction in electrode size and the ability to provide directional stimulation could increase the efficacy of such therapies. This has never been demonstrated in humans. In the present study, we assess the effect of directional stimulation compared to omnidirectional stimulation. Three different directions of stimulation as well as omnidirectional stimulation were tested intraoperatively in the subthalamic nucleus of 11 patients with Parkinson's disease and in the nucleus ventralis intermedius of two other subjects with essential tremor. At the trajectory chosen for implantation of the definitive electrode, we assessed the current threshold window between positive and side effects, defined as the therapeutic window. A computed finite element model was used to compare the volume of tissue activated when one directional electrode was stimulated, or in case of omnidirectional stimulation. All but one patient showed a benefit of directional stimulation compared to omnidirectional. A best direction of stimulation was observed in all the patients. The therapeutic window in the best direction was wider than the second best direction (P = 0.003) and wider than the third best direction (P = 0.002). Compared to omnidirectional direction, the therapeutic window in the best direction was 41.3% wider (P = 0.037). The current threshold producing meaningful therapeutic effect in the best direction was 0.67 mA (0.3-1.0 mA) and was 43% lower than in omnidirectional stimulation (P = 0.002). No complication as a result of insertion of the directional electrode or during testing was encountered. The computed model revealed a volume of tissue activated of 10.5 mm(3) in omnidirectional mode, compared with 4.2 mm(3) when only one electrode was used. Directional deep brain stimulation with a reduced electrode size applied intraoperatively in the subthalamic nucleus as well as in the nucleus ventralis intermedius of the thalamus significantly widened the therapeutic window and lowered the current needed for beneficial effects, compared to omnidirectional stimulation. The observed side effects related to direction of stimulation were consistent with the anatomical location of surrounding structures. This new approach opens the door to an improved deep brain stimulation therapy. Chronic implantation is further needed to confirm these findings.

无阈值窗口傅里叶变换滤波法

In order to reduce the speckle noise in phase distribution of deformation,a non-threshold windowed Fourier filter algorithm was proposed.The maximal amplitude of stripe frequency is set as the filtering criterion by scanning the amplitude of stripe frequency in the window,which the optimum frequency image is obtained and the threshold window is not set in the window Fourier filter algorithm.And the proposed algorithm is used on the fringe patterns.Experiment results show that the proposed algorithm have a better performance in reducing the speckle noise and a high precision in phase calculation.The algorithm proposed can be used to filter other images as a low-pass filter.

Determining the Time Window Threshold to Identify User Sessions of Stakeholders of a Commercial Bank Portal

In this paper, we focus on finding the suitable value of the time threshold, which is then used in the method of user session identification based on the time. To determine its value, we used the Length variable representing the time a user spent on a particular site. We compared two values of time threshold with experimental methods of user session identification based on the structure of the web: Reference Length and H-ref. When comparing the usefulness of extracted rules using all four methods, we proved that the use of the time threshold calculated from the quartile range is the most appropriate method for identifying sessions for web usage mining.

Classification and volumetric analysis of temporal bone pneumatization using cone beam computed tomography

This study performed volumetric analysis and classified different repeated patterns of temporal bone pneumatization in adults using cone beam computed tomography (CBCT) scans. A total of 155 temporal bones were retrospectively evaluated from 78 patients with no radiographic evidence of pathology. Two reference structures were used to classify temporal bone pneumatization into 3 groups. Volumetric analysis of the pneumatization was performed using a window thresholding procedure on multiplanar CBCT images. Correlation between direct communication of peritubal cells with the eustachian tube and the degree of pneumatization was also assessed. Using 2 reference structures, pneumatization pattern in the temporal bone can be classified into 3 groups. Statistically significant differences were present in their mean volumes between 3 groups. Statistically significant correlation was found between degree of pneumatization and presence of peritubal cells associated with ET. This study showed that CBCT can be effectively used for imaging temporal bone air cavities and for volumetric assessment.

Fault Detection of Carbide Anvil Based on Hurst Exponent and BP Neural Network

This paper proposed a novel diagnosis algorithm based on Hurst exponent and BP neural network to detect carbide anvil fault in synthetic diamond industry. Firstly, a sort of preprocessing algorithm is proposed, which uses the sliding window and energy threshold method to separate the pulse from initial continuous signal. Then, some characteristic parameters which are based on Hurst exponent are extracted from the separated pulse signal. These characteristic parameters are used to construct fault characteristic vectors. Finally, the BP neural network model was established for fault recognition. Experimental results show that the proposed fault detection method has high recognition rate of 96.7%.

Auto term window method and its parameter selection

In this paper, the parameter selection in Auto term window (ATW) method is discussed and analyzed in the theoretical and experimental analysis. ATW method can suppress cross terms in Wigner–Ville distribution (WVD) effectively and applied in rotary machinery feature extraction and fault diagnosis. According to the characteristic that the auto terms and cross terms have no correlation, the ATW method introduces a window function which covers the auto terms in the time–frequency domain to windowing the WVD results. Aimed at the two difficulties in this new method which are window function selection and threshold value determination, this paper discusses the parameters optimization process in detail. The suitable window function with good time–frequency distribution and energy accumulation has been selected and compared to some other existent approaches. The optimal parameters are determined in the following analysis and the simulation examples are used to prove the validation of the results.

Comparison of gamma (Anger) camera systems in terms of detective quantum efficiency using Monte Carlo simulation

The aim of the present study was to perform an extensive evaluation of available gamma camera systems in terms of their detective quantum efficiency (DQE) and determine their dependency on relevant parameters such as collimator type, imaging depth, and energy window using the Monte Carlo technique. The modulation transfer function was determined from a simulated (99m)Tc point source and was combined with the system sensitivity and photon yield to obtain the DQE of the system. The simulations were performed for different imaging depths in a water phantom for 13 gamma camera systems from four manufacturers. Except at very low spatial frequencies, the highest DQE values were found with a lower energy window threshold of around 130 keV for all systems. The height and shape of the DQE curves were affected by the collimator design and the intrinsic properties of the gamma camera systems. High-sensitivity collimators gave the highest DQE at low spatial frequencies, whereas the high-resolution and ultrahigh-resolution collimators showed higher DQE values at higher frequencies. The intrinsic resolution of the system mainly affected the DQE curve at superficial depths. The results indicate that the manufacturers have succeeded differently in their attempts to design a system constituting an optimal compromise between sensitivity and spatial resolution.

A window detection technique with adjustable threshold for transmitted reference receivers

Abstract This paper presents a threshold decision circuit with an adjustable detection window designed in a 90-nm IBM CMOS technology. Together with an RF mixer, the decision Section realizes the circuit implementation of the back-end of a transmitted reference ultra wideband receiver, which is yet to be reported in literature. The proposed circuit is built on a differential amplifier core and avoids the use of integrator and sampling blocks, which reduces the device burden necessary for the architecture. Moreover, the detection window threshold of the design can be regulated by three independent factors defined by the circuit elements. The circuit is tested at an input data rate of 0.1∼2.0 Gbps and the core decision section consumes 9.14 mW from a 1.2-V bias supply (with a maximum capacity/Pdc ratio of 218.8 GHz/W). When compared against other reported decision blocks, the proposed detection circuit shows improved performance in terms of capacity and power requirement.

Field gamma dose-rate assessment in natural sedimentary contexts using LaBr3(Ce) and NaI(Tl) probes: A comparison between the “threshold” and “windows” techniques

Results are presented for a series of replicate in situ gamma spectrometry measurements (n=20) made in natural sedimentary contexts using LaBr3(Ce) and NaI(Tl) probes. For both types of detectors, gamma dose rates were calculated using the “threshold” technique (Murray et al., 1978), and compared with results obtained previously by Arnold et al. (2012) using the “windows” technique (Aitken, 1985). Our results show that gamma dose rates obtained using these two techniques are consistent at 1σ for a given probe, and that the threshold technique yields reproducible results for the LaBr3(Ce) and NaI(Tl) probes. In comparison with the energy windows approach, the threshold approach offers an improvement in the precision with which gamma dose rates can be determined using the LaBr3(Ce) probe. The potential of an alternative threshold approach (the “energy threshold” approach of Guérin and Mercier, 2011) was also tested for both probe types, and the resultant gamma dose rates were found to be in agreement with those obtained using the standard threshold and energy windows techniques.Our results provide new insights into methods and instrumentation used for assessing in situ gamma dose rates in Electron Spin Resonance (ESR) and Luminescence dating. We conclude that LaBr3(Ce) probes can reliably be used for portable gamma dosimetry in low level activity sedimentary environments (500–1500μGy/a) when using the threshold approach, provided that their non-negligible internal background activities (equivalent to ∼758μGy/a for our probe) are accurately assessed and subtracted from gamma ray spectra measured in the field. Our results also suggest that there may be some minor merit in applying an internal background-subtraction procedure to NaI(Tl) gamma ray spectra when using the threshold technique, in spite of the lower intrinsic activities of NaI(Tl) detectors.

New Segmentation Approach to Extract Human Mandible Bones Based on Actual Computed Tomography Data

In this paper, a new approach for segmenting different anatomical regions in dental Computed Tomography (CT) studies is presented. The approach consists of three steps: Hounsfield unit's threshold (HU) based on gray-level segmentation, multi-object with texture extraction and anatomical regions identification. First, a HU threshold window sets to separate between different regions upon their gray-level values; second, a set of objects are generated by and texture descriptors are calculated for selected windows from the image data sample. Finally, identification of different anatomical regions set for mandible bones cortical and cancellous. It is expected that the proposed approach will also help automate different semi-automatic segmentation techniques by providing initial boundary points for deformable models or seed points for split and merge segmentation algorithms. Preliminary results obtained for dental CT studies of human-mandible are presented.

QoS aware transmission control scheme for multihop WiMAX network

SUMMARYThe IEEE 802.16j Mobile Multihop Relay (MMR) WiMAX network allows the number of hops between the end user and the base station to be more than two hops. It supports non‐real‐time Polling Service, which considers the minimum reserved rate and the maximum sustained rate as a QoS requirements. The reliability of sending the data over MMR WiMAX is achieved by using Transmission Control Protocol (TCP) in transport layer and automatic repeat request in the link layer. However, the use of automatic repeat request in the link layer makes the round trip time fluctuate rapidly, which increases the possibility of retransmission timeout (RTO) expiration. TCP performance degrades because of frequent timeout, and hence the QoS transmission rates cannot be satisfied. Therefore, this paper presents an RTO smoothing scheme and QoS aware transmission control to enhance the performance of data transmission over MMR WiMAX networks. The RTO smoothing scheme aims to reduce the frequent timeout occurrences. The slow start threshold and maximum congestion window are adjusted to satisfy the required QoS and it provides transmission rate fairness for the users at different hops. The results showed that, the proposed schemes reduce the timeout, and improve the utilization of the allocated resources and TCP throughput. Copyright © 2012 John Wiley & Sons, Ltd.

A Novel Cross-layer Congestion Control Strategy for Wireless Sensor Networks

Network congestion in wireless sensor networks (WSNs) leads to packet drops, throughput reduction and degradation of channel quality which in turn decrease network performance. A novel cross-layer congestion control strategy for WSNs is presented. The strategy performs the bandwidth and delay estimation in MAC layer for the current link, and feedbacks them to the transport layer through the cross-layer interaction mechanism. The transport layer of source nodes adjusts the congestion window and slow start threshold based on the received information of path bandwidth and delay and Explicit Congestion Notification (ECN), for mitigating network congestion. The simulation results show that the strategy can improve the utilization of network resources, reduce unnecessary packets retransmission, and significantly improve the performance of WSNs.

Piecewise HIV virus dynamic model with CD4+ T cell count-guided therapy: I

The strategies of structured treatment interruptions (STIs) of antiretroviral therapies have been proposed for clinical management of HIV infected patients, but clinical studies on STIs failed to achieve a consistent conclusion for this strategy. To evaluate the STI strategies, in particular, CD4+ T cell count-guided STIs, and explain these controversial conclusions from different clinical studies, in this paper we propose to use piecewise HIV virus dynamic models to quantitatively explore the STI strategies and investigate their dynamic behaviors. Our analysis results indicate that CD4+ T cell counts can be maintained above a safe level using the STI with a single threshold or a threshold window. Numerical simulations show that the CD4+ T cell counts either fluctuate or approach a stable level for a patient, depending on the prescribed upper or lower threshold values. In particular, the CD4+ T cell counts can be stabilized at a desired level if the threshold policy control is applied. The durations of drug-on and drug-off are very sensitive to the prescribed upper or lower threshold levels, which possibly explains why the on–off strategy with fixed schedule or an STI strategy with frequent switches are associated with the high rate of failure. Our findings suggest that it is critical to carefully choose the thresholds of CD4+ T cell count and individualize the STIs for each individual patient based on initial CD4+ T cell counts.

English

Based on multilayer dielectric model, for the spherical biological cell subjected to pulsed electric field (PEF), a simplified equivalent circuit was presented. According to a mathematical analysis of a monocycle electric pulse (MEP), the relationship between a given pulse duration and a center frequency was established and its main energy was concentrated on the center frequency. Thus the transmenbrane potential of external and inner membranes induced by the MEP with various durations was simply calculated by using a harmonic function with different center frequency and the equivalent circuit equations. Furthermore, the threshold electric intensities and window effect of the electroporation with different pulse duration were discussed assuming that the external and inner membranes would breakdown under certain potential values. In view of current difficulty in developing the high peak power PEF devices and the advantage of the MEP in living cell's electroporation effects, an experimental scheme was presented in which a Gaussian pulse was generated by a photoconductive semiconductor switch (PCSS) and a MEP was produced through a Blumlein transmission line (BTL). Key words: Monocycle pulse, transmenbrane potential, electric intensity threshold, window effect, monocycle pulse generator.

Improving TCP performance with fast adaptive congestion control during soft vertical handoff

Recently, the research on the interworking between 3G cellular networks and WLANs is actively being constructed. To integrate these two technologies, there are many issues such as the network architecture, mobility management, and security which should be solved. During vertical handoff, some undesirable phenomena may mistakenly trigger TCP congestion control operations and thus degrade TCP performance. In this paper, we propose an approach that can quickly estimate available bandwidth when a mobile node (MN) handoff occurs. A sender updates the adaptive slow-start threshold (ssthresh) and congestion window size (cwnd) to improve TCP performance during soft vertical handoff in hybrid mobile networks. Our scheme requires only minor modifications of the transport layer of the end hosts. Simulation results show that our scheme effectively improves the TCP performance.

Symptom Association in Ambulatory Gastro-Esophageal Reflux Monitoring: A Systematic Analysis

Introduction The diagnosis of gastro-oesophageal reflux disease (GORD) by ambulatory reflux monitoring is based on oesophageal acid exposure time (AET) or temporal association of reflux events with patient symptoms. Several key issues required for reflux-symptom association, such as the most appropriate pH threshold and time window, have not been defined and current statistical analysis has important limitations: Symptom Index (SI) is a measure of an effect size, not of confidence. Symptom Association Probability (SAP) is a measure of confidence but not of size and applies the Fisher exact test inappropriately (dividing time into fixed intervals does not produce independent counts). This study presents a systematic assessment of symptom association in ambulatory gastro-oesophageal reflux monitoring data. Methods Acid reflux (pH) and symptom data were acquired by wireless pH recording (Bravo, Given Imaging). 163 consecutive patients presenting with predominantly typical reflux symptoms (heartburn, regurgitation) studied 2006–2009 with duration >3.7 days were studied (636 days). Data were exported in XML format, and analyzed by custom written program. A systematic analysis was performed. Results (1) Symptom markers A finite-state algorithm was developed to equalise patient responses, removing redundant markers in one pass with reflux detection. (2) pH threshold: Setting pH thresholds for reflux detection is not physiological and a weighted S-shaped (‘dose response9) curve could be more appropriate. This was assessed varying the centre and steepness of the curve to maximise association with SI and SAP. A steep S-curve almost indistinguishable to a threshold was found: maximum correlation SI pH threshold 4.5, correlation 0.55; SAP pH threshold 4.4, correlation 0.34. (3) time window: The frequency of reflux associated symptom markers was above baseline only during minute 1. The association in minute 2 was no higher than chance. (4) Over time (day 1–4) SI was stable; however SAP increased progressively. Both parameters increased with the frequency of reflux events. CI for SI were computed by assuming a binomial distribution (Agresti-Coull method). Conclusion A novel approach to symptom association of ambulatory reflux monitoring data is presented. Confounding due to redundant symptom markers is removed by a finite-state algorithm. Acid threshold of pH 4.5 and a time window of 1 min provided optimal correlation with SI. Computing SI with CI provides a statistically valid, single parameter that describes both size of effect and likelihood of association between reflux events and symptoms.