Dynamic Threshold Scheme Research Articles

Dynamic Threshold Finite-Time Prescribed Performance Control for Nonlinear Systems With Dead-Zone Output.

This article investigates the tracking control problem for nonlinear systems. An adaptive model is proposed to represent the dead-zone phenomenon and solve its control challenge with a Nussbaum function in conjunction. Drawing inspiration from the existing prescribed performance control schemes, a novel dynamic threshold scheme is developed that fuses a proposed continuous function with a finite-time performance function. A dynamic event-triggered strategy is applied to reduce the redundant transmission. The proposed time-varying threshold control strategy has fewer updates than the traditional fixed threshold and improves the efficiency of resource utilization. A command filter backstepping approach is employed to prevent the complexity explosion faced by the computation. The suggested control strategy ensures that all system signals are bounded. The validity of the simulation results has been verified.

Dynamic threshold strategy optimization for security protection in Internet of Things: An adversarial deep learning‐based game‐theoretical approach

AbstractAs mobile communications, the Internet, databases, distributed computing, and other technologies continue to develop, the Internet of Things (IoT) has emerged as prevalent technique. However, attacks on security and sensitive data in IoT occur frequently, and these attacks often evade intrusion detection systems strategically by mutating their traffic. To prevent security threats and sensitive data leakage, we propose a game approach based on adversarial deep learning to optimize a dynamic security threshold strategy. We introduce a mobile edge computing framework and utilize a game model to describe the adversarial interaction between the two participants. To solve the complexity of the game problem to gain dynamically randomized adversarial attacks, we present a column generation (CG) framework, which uses a feedforward neural network to quantify data flowing through IoT devices. Considering the limited resources of IoT devices, we calculate an optimal response to cyberattacks via a particle swarm optimization algorithm, aiming to reduce the false alarm rate. The adversarial dynamic threshold (ADT)‐based column generation (CG‐ADT) algorithm generates the set of detection threshold and the probability. Finally, we present the results of experiments conducted to demonstrate the effectiveness and robustness of the proposed dynamic threshold scheme for sensitive data security protection in IoT and its suitability for implementation in production systems.

Enhanced chiller faults detection and isolation method based on independent component analysis and k-nearest neighbors classifier

The fault detection and isolation (FDI) of centrifugal chiller system is essential for improving energy efficiency and reducing energy consumption. Considering the non-Gaussianity of chiller measurement, this paper proposes an effective non-Gaussian chiller FDI method based on independent component analysis (ICA) and k-nearest neighbor (KNN) classifier. First of all, an enhanced fault detection method is developed by combining exponentially weighted moving average and ICA (EWICA). The exponentially weighted moving average is employed to develop a dynamic threshold scheme, which reduces the false alarm rate (FAR) and improves the fault detection rate (FDR) of chiller faults. Then, based on the KNN with cosine similarity metric, a novel fault isolation method using the direction of the residual vector is presented to isolate the chiller faults. To further improve the isolation performance, the number of neighbors (k) is optimized by 10-fold cross validation. Finally, the proposed FDI method is validated by using a data set from the ASHRAE Research Project 1043 (RP-1043). The FDI performance of the proposed method is comprehensively analyzed and compared with six state-of-the-art methods. Both of detection and isolation results suggest that the EWICA-based method delivers superior performance for chiller FDI.

Capacity-Achieving Codes That Mitigate Intercell Interference and Charge Leakage in Flash Memories

We investigate constant-composition constrained codes for the mitigation of intercell interference for multilevel cell flash memories with a dynamic threshold scheme. The first explicit formula for the maximum size of a $q$ -ary ${\mathcal F}$ -avoiding code with a given composition and certain families of substrings ${\mathcal F}$ is presented. In addition, we provide methods to determine the asymptotic rate for ${\mathcal F}$ -avoiding codes with any composition ratio and to find the optimal composition ratio that maximizes the asymptotic rate. We also give the first efficient encoder/decoder for these $q$ -ary constant-composition codes achieving the channel capacity, for all $q$ values.

Monitoring Wind Turbine Gearbox with Echo State Network Modeling and Dynamic Threshold Using SCADA Vibration Data

Health monitoring of wind turbine gearboxes has gained considerable attention as wind turbines become larger in size and move to more inaccessible locations. To improve the reliability, extend the lifetime of the turbines, and reduce the operation and maintenance cost caused by the gearbox faults, data-driven condition motoring techniques have been widely investigated, where various sensor monitoring data (such as power, temperature, and pressure, etc.) have been modeled and analyzed. However, wind turbines often work in complex and dynamic operating conditions, such as variable speeds and loads, thus the traditional static monitoring method relying on a certain fixed threshold will lead to unsatisfactory monitoring performance, typically high false alarms and missed detections. To address this issue, this paper proposes a reliable monitoring model for wind turbine gearboxes based on echo state network (ESN) modeling and the dynamic threshold scheme, with a focus on supervisory control and data acquisition (SCADA) vibration data. The aim of the proposed approach is to build the turbine normal behavior model only using normal SCADA vibration data, and then to analyze the unseen SCADA vibration data to detect potential faults based on the model residual evaluation and the dynamic threshold setting. To better capture temporal information inherent in monitored sensor data, the echo state network (ESN) is used to model the complex vibration data due to its simple and fast training ability and powerful learning capability. Additionally, a dynamic threshold monitoring scheme with a sliding window technique is designed to determine dynamic control limits to address the issue of the low detection accuracy and poor adaptability caused by the traditional static monitoring methods. The effectiveness of the proposed monitoring method is verified using the collected SCADA vibration data from a wind farm located at Inner Mongolia in China. The results demonstrated that the proposed method can achieve improved detection accuracy and reliability compared with the traditional static threshold monitoring method.

Dust Detection and Intensity Estimation Using Himawari-8/AHI Observation

In this study, simple dust detection and intensity estimation methods using Himawari-8 Advanced Himawari Imager (AHI) data are developed. Based on the differences of thermal radiation characteristics between dust and other typical objects, brightness temperature difference (BTD) among four channels (BT11–BT12, BT8–BT11, and BT3–BT11) are used together for dust detection. When considering the thermal radiation variation of dust particles over different land cover types, a dynamic threshold scheme for dust detection is adopted. An enhanced dust intensity index (EDII) is developed based on the reflectance of visible/near-infrared bands, BT of thermal-infrared bands, and aerosol optical depth (AOD), and is applied to the detected dust area. The AOD is retrieved using multiple temporal AHI observations by assuming little surface change in a short time period (i.e., 1–2 days) and proved with high accuracy using the Aerosol Robotic Network (AERONET) and cross-compared with MODIS AOD products. The dust detection results agree qualitatively with the dust locations that were revealed by AHI true color images. The results were also compared quantitatively with dust identification results from the AERONET AOD and Ångström exponent, achieving a total dust detection accuracy of 84%. A good agreement is obtained between EDII and the visibility data from National Climatic Data Center ground measurements, with a correlation coefficient of 0.81, indicating the effectiveness of EDII in dust monitoring.

An Adaptive Measurement Report Period and Handoff Threshold Scheme Based on SINR Variation in LTE-A Networks

This paper deals with the problem of triggering handoff procedure at an appropriate point of time to reduce the ping-pong effect problem in the long-term evolution advanced (LTE-A) network. In the meantime, we also have studied a dynamic handoff threshold scheme, named adaptive measurement report period and handoff threshold (AMPHT), based on the user equipment’s (UE’s) reference signal received quality (RSRQ) variation and the moving velocity of UE. AMPHT reduces the probability of unnecessarily premature handoff decision making and also avoids the problem of handoff failure due to too late handoff decision making when the moving velocity of UE is high. AMPHT is achieved by two critical parameters: (1) a dynamic RSRQ threshold for handoff making; (2) a dynamic interval of time for the UE’s RSRQ reporting. The performance of AMPHT is validated by comparing numerical experiments (MATLAB tool) with simulation results (the ns-3 LENA module). Our experiments show that AMPHT reduces the premature handoff probability by 34% at most in a low moving velocity and reduces the handoff failure probability by 25% in a high moving velocity. Additionally, AMPHT can reduce a large number of unnecessary handoff overheads and can be easily implemented because it uses the original control messages of 3GPP E-UTRA.

Dynamic Threshold Schemes for Multi-Level Non-Volatile Memories

In non-volatile memories, reading stored data is typically done through the use of predetermined fixed thresholds. However, due to problems commonly affecting such memories, including voltage drift, overwriting, and inter-cell coupling, fixed threshold usage often results in significant asymmetric errors. To combat these problems, Zhou, Jiang, and Bruck recently introduced the notion of dynamic thresholds and applied them to the reading of binary sequences. In this paper, we explore the use of dynamic thresholds for multi-level cell (MLC) memories. We provide a general scheme to compute and apply dynamic thresholds and derive performance bounds. We show that the proposed scheme compares favorably with the optimal thresholding scheme. Finally, we develop limited-magnitude error-correcting codes tailored to take advantage of dynamic thresholds.

On dealer-free dynamic threshold schemes

In a threshold scheme, the sensitivity of the secret as well as the number of players may fluctuate due to various reasons, e.g., mutual trust may vary or the structure of the players' organization might be changed. A possible solution to this problem is to modify the threshold and/or change the secret. Moreover, a common problem with almost all secret sharing schemes is that they are 'one-time', meaning that the secret and shares are known to everyone after a public secret recovery process. This problem could be resolved if the dealer shares various secrets at the beginning, but a better solution is to dynamically generate new secrets in the absence of the dealer. These issues are our main motivation to revisit dynamic threshold schemes. Therefore, we first provide the first comprehensive study of threshold modification techniques in both the passive and active adversary models. We first review an existing method for threshold modificationbased on resharing shares of a secret; this method is secure in the setting of a passive adversarialcoalition. We then discuss two methods, termed public evaluation (for thresholdreduction) and zero addition (for threshold increase) that can be used in both the passive andactive adversarial setting. In the case of an active adversary, the techniques makeuse of verifiable secret sharing schemes, whereas the schemes considered in the passiveadversary model are all based on the Shamir scheme.As an application, we discuss how the threshold and the secret can be changed multiple timesto arbitrary values after the scheme's initialization.

Performance Improvement of OOK Free-Space Optical Communication Systems by Coherent Detection and Dynamic Decision Threshold in Atmospheric Turbulence Conditions

In this letter, we analyze the performance improvement of on–off-keying free-space optical communication systems in atmospheric turbulence conditions due to coherent detection and the dynamic decision threshold (DDT) scheme. Our analytical results show that the DDT scheme provides a 5.7-dB power reduction for achieving a bit error rate of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$10^{-3}$</tex></formula> compared with the conventional fixed decision threshold scheme. In addition, the improvement achieved by the DDT scheme is related to the strength of amplitude and phase fluctuations, not to the power of the local oscillator.

지문 식별을 위한 동적 임계치 설정방법

Abstract: This paper proposes dynamic thresholding scheme for fingerprint identification. As a user authentication method by fingerprint recognition technology, verification method based on 1:1 matching was mainly used in the past, but identification method based on 1:N matching is generally used recently. The control of the value of FAR is very important in the application areas such as access control and time attendance systems. This paper proposes dynamic thresholding scheme which could properly control the value of FAR according to the field of applications and size of the fingerprints database.Keywords: labeling, feature, defect inspection, neighbor Copyright© ICROS 2012 1.FAR FRR(%).Table1.FAR, FRR Value for a Security Level (%).0 1 2 3 4FAR(%)1.00060.50100.25150.10000.0316FRR(%)0.11900.14800.22200.34100.54905 6 7 8 9FAR(%)0.0100.00310.0010.00030.0001FRR(%)0.7861.05301.3351.83902.5800I. 서론  !#$%&'()*+,-. ./,0123456789 5:%&, ; ?@AB&C D2 EF-F:,3GHIJKL< MNHIOP#QR%&,RL<S%T, UVF4W5XJ8YZ&2F-[5RL\]-[1]. ^_`3a%& bc def\gh%&i LT, f\ghjklmn,Iopq4qrsq4%&tu<v-. wxy,QRLFlmn(minutiae) 1a f\gh]<lmn,Iopq48z{x|}~€, bc B2‚xNƒg, 0„ †‡p, ‚x,vˆ, |„ˆ‰ƒgq48ŠdkLT, ,5q48w‹ lmn,IŒgF0„Žn, 1nde † 8op#]-[2,3].‘ %&HIoplmn,IrsH’“$21‹Flmn”12•–Q 8—2rsn#’˜™2T, ˜™rsn#šg4‹v›˜(threshold value)8œFž‘ ,rs:%&“$5-. 35 rsf\ghB2›˜8Dˆ^Ÿ€  (FAR: False Acceptance Ratio) ŠHi(FRR: False Rejection Ratio),DˆLT, ¢R

Optimization of threshold for local spectrum sensing with energy detector

Spectrum sensing is the first step of cognitive radio (CR). In this area, previous researches mostly consider distributed local nodes which are under identical channel conditions, hence uniform and fixed detection threshold is set with energy detector. However, the distributions of nodes in real environments are not quite the same. In this paper, the optimal threshold to minimize the total detection error over additive white Gaussion noise (AWGN) channel is derived firstly. Then the dynamic threshold scheme is proposed to reduce the average total detection error. Simulations have shown that, with this scheme, sensing performance is improved.

WE‐E‐224C‐04: A New CT Reconstruction Technique for Removal of Streak Artifacts Due to Metallic Dental Fillings and Implants for the Treatment of Head and Neck Cancer with Intensity Modulated Radiation Therapy

Purpose: To remove or reduce the streak artifacts induced by metallic dental fillings and implants in CT images for head and neck patients treated with intensity modulated radiation therapy (IMRT). Materials and Method: A cylindrical phantom was constructed using tissue‐equivalent plastic to simulate a human head. The phantom was filled with distilled water. A piece of 1 cm‐wide half elliptic tissue‐equivalent bolus was attached to a thin circular plastic plate inside the phantom to mimic the gingiva. Two human second molars with metallic fillings were implanted into the bolus on each side. The phantom was scanned on a GE LightSpeed CT scanner with a slice thickness of 2.5 mm. The acquired CT images were first decomposed into spatio‐frequency components using a wavelet transform. The decomposition tree allowed us to examine and characterize different localized frequency information related to undesired artifacts. Once the spatio‐frequency signatures of metal objects were modeled, the corresponding coefficients in the wavelet domain were thresholded using a dynamic thresholding scheme. The thresholded images gave metal objets, which were then superimposed on a neighbor slice. New data were generated by re‐projecting the original slice and superimposed slice. The final image was reconstructed with no or reduced image artifacts due to dental fillings and implants. Results: Comparison of original images to reconstructed images indicates that the streak artifacts were either completely removed or significantly reduced. The structural details near the metal objects were clearly identifiable. The image quality was sufficient for target delineation in IMRT treatment planning. Conclusions: The proposed technique can greatly reduce the streak artifacts induced by metallic dental fillings and implants without sacrifice of spatial resolution. The technique has the potential to significantly improve the accuracy of target and critical organ delineation and dose calculation in the head and neck IMRT treatment planning.

Dynamic queue length thresholds for multiple loss priorities

Buffer management schemes are needed in shared-memory packet switches to regulate the sharing of memory among different output port queues and among traffic classes with different loss priorities. Earlier, we proposed a single-priority scheme called dynamic threshold (DT), in which the maximum permissible queue length is proportional to the unused buffering in the switch. A queue whose length equals or exceeds the current threshold value may accept no new arrivals. We propose, analyze and simulate several ways of incorporating loss priorities into the DT scheme. The analysis models sources as deterministic fluids. We determine how each scheme allocates buffers among the competing ports and loss priority classes under overload conditions. We also note how this buffer allocation induces an allocation of bandwidth among the loss priority classes at each port. We find that minor variations in the DT control law can produce dramatically different resource allocations. Based on this study, we recommend the scheme we call OWA, which gives some buffers and bandwidth to every priority class at every port. Scheme OWA has tunable parameters, which we give rules of thumb for setting. Another scheme, called AWA, is also a good choice. It has an allocation philosophy more akin to strict priority and hence is not tunable.

A note on the randomness in dynamic threshold schemes

In dynamic threshold schemes the dealer is able (after a preprocessing stage) to allow sets of participants of a given cardinality to reconstruct different secrets (in different time instants) by sending them the same broadcast message. In this paper we provide a tight lower bound on the number of random bits needed by the dealer to set up a dynamic threshold scheme.

A new SOI inverter using dynamic threshold for low-power applications

A new SOI inverter using the dynamic threshold (DT) that lowers threshold voltage of MOSFET only in active operation of a logic circuit is proposed for high-speed and low-power applications. The dynamic threshold scheme is realized by dynamically biasing the body of MOSFET's. The SOI MOSFET's have been designed and fabricated to take full advantage of the reverse body effect which is affected by many device parameters. From the measurements and simulations, the proposed scheme is shown to be useful in the buffer with large load conditions and low supply voltage if the SOI MOSFET's are properly designed.

Efficient Image Matching: A Hierarchical Chamfer Matching Scheme Via Distributed System

Image matching has played a key role in object recognition and localization. One central problem is to find an efficient and effective approach to search for the best matching between two image sets. In contrast to the conventional matching techniques, the innovation of our method detailed in this paper is to propose a hierarchical Chamfer matching scheme based on the dynamic detection of interesting points. The algorithm extends the traditional methods by introducing interesting points to replace edge points in distance transform for the matching measurement. The search for the best matching is guided by minimizing a given matching criterion in an interesting points pyramid from coarse level to fine level. The pyramid is created through a dynamic thresholding scheme and such a hierarchical structure aims to reduce the computation load. The processing speed is further improved by parallel implementation on a low cost heterogeneous PVM (Parallel Virtual Machine) network without specific software and hardware requirements. The experimental results demonstrate that our algorithm is simple to implement and quite insensitive to noise and other disturbances with reliability and efficiency.

A note on dynamic threshold schemes

An ( m, n, T) dynamic threshold scheme is a method to distribute T secrets, s 1,…, s T , among a set of n participants in such a way that subsets of participants of size at least m can reconstruct the secret S i only after seeing a message b i which is broadcasted to all participants, whereas any subset of participants of size less then m has absolutely no information on any of the secrets S i , even after seeing all broadcast messages. In this paper we provide lower bounds both on the size of the information held by each participant in the scheme and on the size of the broadcast messages. Our lower bounds are tight as we provide a scheme achieving them. Our model is a generalization of the one recently proposed by Sun and Shieh [12]. The scheme we provide is simpler, more efficient from a computational point of view, and uses smaller broadcast messages than that in [12].

Construction of dynamic threshold schemes

An (m, n) threshold scheme is to decompose a shared secret into n shares in such a way that the shared secret cannot be reclaimed unless any m shares are collected. A new dynamic threshold scheme that allows the shared secret to be updated without changing the shares is proposed.

On dynamic threshold schemes

An ( m, n) threshold scheme is to decompose the master key K into n secret shadows in such a way that the master key K cannot be reclaimed unless any m shadows are collected. However, any m − 1 or fewer shadows provide absolutely no information about K. In 1989, Laih et al. proposed the concept of dynamic threshold schemes which allow the master key to be updated without changing the secret shadows. However, the perfect dynamic threshold scheme, which provides perfect secrecy though the master key is allowed to be changed, has not been proposed. Nor has any paper shown the existence of perfect dynamic threshold schemes. In this paper, we prove that perfect dynamic threshold schemes do not exist when their master keys need be updated ⌊ log 2 | S| log 2 | K| ⌋ times or more without changing the secret shadows, where S is the secret shadow space and K is the master key space. Furthermore, we propose an perfect dynamic threshold scheme which allows its master key to be updated once without changing the secret shadows.