Instability Detection Method Research Articles

An Innovative and Accurate Next-Generation Sequencing–Based Microsatellite Instability Detection Method for Colorectal and Endometrial Tumors

The detection of microsatellite instability (MSI) and mismatch repair (MMR) deficiency has become mandatory for most tumors in recent years, owing to the development of immune checkpoint inhibitors as a highly effective therapy for MMR deficiency/MSI tumors. The timely and efficient detection of MSI is valuable, and new methods are increasingly being developed. To date, MMR assessment has been performed using immunohistochemistry of the 4 MMR proteins and/or microsatellite stability/MSI using PCR, mostly using the pentaplex panel. The implementation of next-generation sequencing (NGS) for MSI analysis would improve the effectiveness at a lower cost and in less time. This study describes the development of 8 new microsatellites combined with a classification algorithm, termed “Octaplex CaBio-MSID” (for Cancérologie Biologique MSI Detection tool), to assess MSI using NGS. A series of 303 colorectal cancer and 88 endometrial cancer samples were assessed via MSI testing using NGS using the Octaplex CaBio-MSID algorithm. The sensitivity and specificity of Octaplex CaBio-MSID were 98.4% and 98.4% for colorectal cancers, and 89.3% and 100% for endometrial cancers, respectively. This new NGS-based MSI detection method outperforms previously published methods (ie, Idylla [Biocartis], OncoMate MSI Dx [Promega], and Foundation One CDx [Roche Foundation Medicine]). Although highly efficient, Octaplex CaBio-MSID requires validation in a larger independent series of different tumor types.

Plausibility and Implications of Converter-Driven Oscillations Induced by Unstable Long-Term Dynamics

For decades, synchronous generators have dominated power system dynamics and have been the foundation for the comprehension of the physical phenomena involved in power system stability. This paradigm is rapidly changing; large synchronous generators that contribute to system strength are being replaced by inverter-based generators. Consequently, new kinds of instabilities are emerging. Slow-interaction converter-driven instability is one example in which undamped oscillations occur when inverter-based generators operate in weak areas. Transmission system operators have observed the phenomenon under the scope of short-term dynamics following a disturbance during a weak operating condition. This paper suggests that converter-driven oscillations can occur even in the case when the system's initial operating condition is strong. It concludes that the phenomenon can be triggered by long-term dynamics that slowly weaken the system in which small-signal and short-term simulations show an ample stability margin. The outcome is a combination of unstable long-term dynamics and undamped oscillations. Furthermore, this work suggests that classical emergency controllers that are effective against long-term instability may not be successful if undamped oscillations are also present. A method for instability detection and counteraction is proposed based on Prony analysis and time-domain simulations on the IEEE test system for voltage stability assessment.

Identification of inducer cavitation instabilities using high-speed visualization

This paper presents a new inducer cavitation instability detection method based directly on quantitative high-speed visualization. The new method uses the grayscale values of pixels, representing fluctuations in the cavity structure, to identify cavitation instability. The method is validated against unsteady pressure measurements in two- and three-bladed inducers. Both unsteady pressure measurements and grayscale fluctuations have been analyzed in the frequency domain via Fourier transformation and traveling wave energy analysis to establish the correspondence between the two types of data. Finally, the new method is applied to demonstrate its capability to detect alternate blade cavitation in a 2-bladed inducer and super-synchronous rotating cavitation in a 3-bladed inducer.

Abstract 2080: Tumor microsatellite instability detection method using paired tumor-normal sequence data

Abstract Background: Microsatellite instability (MSI) is an important indicator of larger genome instability and has been linked to many genetic diseases. MMR gene mutations usually lead to the loss of MMR proteins, resulting in high instability of tumor DNA microsatellites (MSI-H), and leading to a high tumor mutation burden (TMB-H). In current clinical practice, MSI detection is performed by experimental methods such as MSI-PCR and MMR-IHC. However, the PCR-based detection procedure is laborious and time-consuming, the accuracy of the results depends on the naked eye judgment of the analysts. With the development of next-generation sequencing (NGS) technology, a large number of MSI detection software based on high-throughput sequencing data have been developed. In this study, we compared the two methods provide a computational method that quantifies MSI status based on genome sequencing data. Methods: 2523 tested samples, including 80 MSI-H samples and 2443 MSS samples, detected by MSI-PCR and NGS-Seq simultaneously, were enrolled in this study. In the MSI-PCR method, MSI status was classified as Microsatellite stable (MSS) and MSI-high (MSI-H, over 2 markers unstable). For the NGS-Seq method, the status of 54 microsatellite site was evaluated by the MSI sensor (https://github.com/ding-lab/msisensor) and the proportion of unstable microsatellite site (RatioUMS) was calculated, and MSI status was classified as MSS (RatioUMS<35), MSS-To Be Determined (MSI-TBD, 35≤RatioUMS≤55), and MSI-H (RatioUMS>55). For MSI-TBD, either TMB is greater than 30 (TMB>30) or TMB is greater than 10 and had a non-silent mutation in an MMR gene (TMB>10&MMR+), MSI-H is considered, otherwise, MSS is considered. Results: In our test, NGS results were inconsistent with MSI-PCR method in 8 samples, among which 5 samples were categorized incorrectly by MSI-PCR after reverification. According to the above results, the consistency of two methods was 99.9%. We also tested the classifier using 114 microsatellite sites in 425 samples and 309 microsatellite sites in 2098 samples. Compared with MSI-PCR, the consistency was 100% and 99.6%, respectively. For the 25 MSI-TBD samples, adding two parameters, MMR gene mutation and TMB, greatly improved the accuracy of the judgment. Conclusion: The results show NGS method are highly consistent with the gold standard MSI-PCR, and the judgmental errors caused in MSI-PCR by human factors can be avoided. The different number of microsatellite sites used in the NGS method has little effect on the final results. NGS approach offers the advantages to simultaneous detection of predictive markers, including MSI, TMB and clinically relevant genomic alterations, will save valuable material, time and costs, which can provide more comprehensive and reasonable recommendations for medication and treatment. Citation Format: Hongling Yuan, Danhua Wang, Honglin Zhu. Tumor microsatellite instability detection method using paired tumor-normal sequence data [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2080.

Transient instability detection method based on multi-source trajectory information

Online monitoring of dynamic stability in wide-area power system is an important condition to reduce the negative impact of out-of-step oscillations. Research shows that during the oscillation of power system, the characteristics of the disturbed trajectory can reflect the instability of the system. Benefiting from the popularization and perfection of wide area measurement system, the transient instability criterion based on the disturbed trajectory analysis has made great progress in recent years. This paper summarizes the six common instability criteria based on the disturbed trajectory and explores the relationship between the criteria in the time sequence. According to the obtained relationship, a comprehensive strategy is constructed to integrate the criteria based on multi-source trajectory information. The multiple criteria are divided by the logic of early warning and judgment, in order to enhance the reliability of transient instability detection and save time for the calculation of the real-time islanding strategy. Simulation results using the IEEE 118 bus system show that the proposed strategy gives high reliability to the system in different scenarios.

Voltage instability detection based on the concept of short circuit capacity

Summary This paper proposes an online detection method for power system voltage instability, which considers the internal impedances of generators and the voltage-dependent and recovery characteristics of the electric loads. First, a novel voltage stability analysis method based on the concept of short circuit capacity (SCC) is established. Based on it, a SCC-based voltage stability index (VSI) is defined as the ratio of the SCC supplied by the combined generation-transmission system and the SCC required by load bus to maintain voltage stability. Then, for the calculation of SCC-based VSI, a two-step equivalent method of power system is presented to obtain the SCC supplied by the system side, in which the generator is modeled as a time-varying internal voltage behind constant internal impedance. Meanwhile, a modification method of load power is proposed to deal with the voltage-dependent characteristics and the restoration dynamics of system loads. As a result, the SCC required by loads can be precisely calculated. At last, the 5-bus system and the New England 39-bus system are used to validate the effectiveness of the proposed voltage instability detection method. Copyright © 2015 John Wiley & Sons, Ltd.

Real-time transient instability detection based on perturbed voltage trajectories

Summary With the application of phasor measurement unit, the response-based security and stability technology has become a hot topic. In this paper, an engineering transient instability detection method is presented on the basis of the perturbed voltage trajectories. Proceeding from the vulnerable buses of power system, a time-domain perturbed voltage integral is utilized to represent the desynchronization of incoherent generator groups and to assess the real-time transient stability of the system. Different from methods that based on angle trajectories, the proposed method can be applied to incomplete wide-area measurements and adapt to multiswing stability analysis without computing the center of inertia. The proposed approach is robust and has good practical feasibility. It improves the existing work in terms of monitoring scheme and threshold value setting. The proposed method is tested on the IEEE 39-bus system and the China Southern Power Grid. Simulation results show that the proposed method is reliable and can be applied to modern interconnected power systems. Copyright © 2014 John Wiley & Sons, Ltd.

Angle Instability Detection in Power Systems With High-Wind Penetration Using Synchrophasor Measurements

The alternating current machines in a power system have the ability to remain synchronized following a severe disturbance such as loss of generations, line switching, or fault. This is described as power system transient stability. During system transients, the machines will accelerate or decelerate because of the mismatch between electrical torque and mechanical torque. Their power angles will travel and finally settle down to a new equilibrium, if the system has enough stored energy to absorb the disturbance, and rest the system at another steady state. In case of system instability, some machines will have aperiodic angular separation from the rest of the system and finally lose synchronization. Therefore, the power system transient stability is also called angle stability. The total system inertia is an essential force to rest the system transient. The inertias stored in all rotating masses that are connected to a power system, such as synchronous generators and induction motors, typically respond to disturbances voluntarily, without any control actions; however, several types of renewable generation, particularly those with power electronic interfaces, have an inertial response governed by a control function. To ensure bulk power system stability, there is a need to estimate the equivalent inertia available from a renewable generation plant. An equivalent voluntary inertia constant analogous to that of conventional rotating machines can be used to provide a readily understandable metric, such as the angle instabilities detections, because one of the most difficult obstacles for angle instability detection is the knowledge of the real-time generator inertias. This paper explores a method that utilizes synchrophasor measurements to estimate the equivalent inertia of a power source such as synchronous generators or wind turbine generators. This paper also investigates the angle instability detection method for a system with high wind power penetration using the synchrophasor measurements.

Research on Flame Combustion Stability Based on Neural Network

For the use of boiler flame image analysis to detect the boiler flame combustion stability, when the combustion affected by coal, peaking , improper operation or other effects, the flame appeared short pulsation. In general, the traditional detection methods based on gray scale variance can not avoid the impact of flame pulsation on account of the inaccuracy of the boiler combustion stability detection. This paper presents a flame combustion instability detection method based on neural network and selects multiple features which are directly related to the flame stability as neural network input vector. Experiments show that this method can fight off the tiny ripple influence caused by the impurities combustion or peak and simultaneously, greatly improve the detection accuracy and stability.

Study on power system transient instability detection based on wide area measurement system

AbstractIn this paper, a method, which is essential in initiating emergency control measures, is proposed for fast and accurate online detection of transient instability based on real‐time measurement. Under a certain disturbance, the candidate critical cluster (CC) of power system is predicted and refreshed at each sampling step. The method identifies the loss of synchronism at each time step by observing the geometric characteristic of the post‐fault trajectory of the generalized one‐machine equivalent system. Unlike the previous extended equal‐area criterion method, it is unnecessary to calculate the unstable equilibrium point (UEP) during instability detection in this method and some limitations caused by the time‐invariant assumption are also eliminated. Simulations are carried out on the IEEE 50 generator test system and a real power system. The simulation results indicate that the proposed method has the features of reliability and effectiveness in identifying the loss of synchronism with inter‐area mode. Copyright © 2008 John Wiley & Sons, Ltd.

Combustion instability detection using the wavelet detail of pressure fluctuations

A combustion instability detection method that uses the wavelet detail of combustion pressure fluctuations is put forward. To confirm this method, combustion pressure fluctuations in a stoker boiler are recorded at stable and unstable combustion with a pressure transducer. Daubechies one-order wavelet is chosen to obtain the wavelet details for comparison. It shows that the wavelet approximation indicates the general pressure change in the furnace, and the wavelet detail magnitude is consistent with the intensity of turbulence and combustion noise. The magnitude of the wavelet detail is nearly constant when the combustion is stable, however, it will fluctuate much when the combustion is unstable.

A new method for power system transient instability detection

Reliability and computational simplicity are of primary importance in developing on-line instability detection methods. With regard to these requirements, this paper has proposed a new method for instability detection based on generator angles, angular velocities, and their rates of change. According to the developed method, system instability or out-of-step condition is detected by identifying the characteristics-concave or convex-of a surface on which the post-fault system trajectory lies. The variation mode and probabilistic property of the proposed index are investigated by using the 10 machine 39 bus IEEE test system.