• Nuclear Engineering and Technology
• /
• v.39 no.2
• /
• pp.133-142
• /
• 2007

The Electric Power Research Institute (EPRI) demonstrated a method for monitoring the performance of instrument channels in Topical Report (TR) 104965, 'On-Line Monitoring of Instrument Channel Performance.' This paper presents the results of several models originally developed by EPRI to monitor three nuclear plant sensor sets: Pressurizer Level, Reactor Protection System (RPS) Loop A, and Reactor Coolant System (RCS) Loop A Steam Generator (SG) Level. The sensor sets investigated include one redundant sensor model and two non-redundant sensor models. Each model employs an Auto-Associative Kernel Regression (AAKR) model architecture to predict correct sensor behavior. Performance of each of the developed models is evaluated using four metrics: accuracy, auto-sensitivity, cross-sensitivity, and newly developed Error Uncertainty Limit Monitoring (EULM) detectability. The uncertainty estimate for each model is also calculated through two methods: analytic formulas and Monte Carlo estimation. The uncertainty estimates are verified by calculating confidence interval coverages to assure that 95% of the measured data fall within the confidence intervals. The model performance evaluation identified the Pressurizer Level model as acceptable for on-line monitoring (OLM) implementation. The other two models, RPS Loop A and RCS Loop A SG Level, highlight two common problems that occur in model development and evaluation, namely faulty data and poor signal selection

• Journal of Positioning, Navigation, and Timing
• /
• v.4 no.4
• /
• pp.161-171
• /
• 2015

Alternative binary offset carrier (AltBOC) signals can be approximated by four synchronized direct sequence spread spectrum (DSSS) signals, each pair of which is a quadrature phase shift keyed (QPSK) signal at a different frequency. Therefore, depending on the strength of an incoming AltBOC signal, an acquisition technique can reduce the mean acquisition time (MAT) by searching the four DSSS signals asynchronously; the search for each of the four DSSS signals can start at one of the evenly separated hypotheses on the two-dimensional hypothesis space. And detection sensitivity can be improved by multiple levels when different numbers of search results for the same hypothesis are combined. In this paper, we propose a fast AltBOC acquisition technique that has an asynchronous search strategy and efficiently utilizes the output of the four search results to increase the sensitivity level when sensitivity improvement is needed. We provide a complete theoretical analysis and demonstrate with numerous Monte Carlo simulations that the MAT of the proposed technique is much smaller than conventional AltBOC acquisition techniques.

• Journal of Positioning, Navigation, and Timing
• /
• v.4 no.4
• /
• pp.151-160
• /
• 2015

GPS L2C signal is a recently added civil signal to L2 frequency and is constructed by time division multiplexing of civil moderate (L2-CM) and civil long (L2-CL) code signals. While the L2-CM code is 20 ms-periodic and modulates satellite navigation message, the L2-CL code is 1.5s-periodic with 767,250 chips long code sequence and carries no data. Therefore, the L2-CL code signal allows receivers to perform a very long coherent integration. However, due to the length of the L2-CL code, the acquisition of the L2-CL code signal may take too long or require too much hardware resources. In this paper, we propose a three-step ultra-fast L2-CL code acquisition (TSCLA) technique for dual band GPS receivers. In the proposed TSCLA technique, a dual band GPS receiver sequentially acquires the coarse/acquisition (C/A) code signal at L1 frequency, the L2-CM code signal, and the L2-CL code signal to minimize mean acquisition time (MAT). The theoretical performance analysis and numerous Monte Carlo simulations show the significant advantage of the proposed TSCLA technique over conventional techniques introduced in the literature.

• IEIE Transactions on Smart Processing and Computing
• /
• v.6 no.3
• /
• pp.220-227
• /
• 2017

Technology development is leading to the invention of more sophisticated electronics appliances that require long battery life. Therefore, saving power is a major concern in current-day scenarios. A notable source of power dissipation in sequential structures of integrated circuits is due to the continuous switching of high-frequency clock signals, which do not carry any information, and hence, their switching is eliminated by a method called clock gating. In this paper, we have incorporated a recent clock-gating style named Leakage Control Transistor (LECTOR)-based clock gating to drive a multi-stage sequential architectures, and we focus on its performance under three different process corners (fast-fast, slow-slow, typical-typical) through Monte Carlo simulation at 18 GHz clock with 90 nm technology. This gating is found to be one of the best gated approaches for multi-stage architectures in terms of total power consumption.

• Advances in aircraft and spacecraft science
• /
• v.7 no.5
• /
• pp.405-423
• /
• 2020

Non-linear energy sink (NES) is an emerging passive absorber able to mitigate the dynamic response of structures without any external energy supply, resonating with all the modes of the primary structure to control. However, its inherent non-linearities hinder its large-scale use and leads to complicated design procedures. For this purpose, an approximate design approach is herein proposed in a stochastic framework. Since loads are random in nature, the stochastic analysis of non-linear systems may be performed by means of computational intensive techniques such as Monte Carlo simulations (MCS). Alternatively, the Stochastic Linearisation (SL) technique has proven to be an effective tool to investigate the performance of different passive control systems under random loads. Since controlled systems are generally non-classically damped and most of SL algorithms operate recursively, the computational burden required is still large for those problems that make intensive use of SL technique, as optimal design procedures. Herein, a procedure to speed up the Stochastic Linearisation technique is proposed by avoiding or strongly reducing numerical evaluations of response statistics. The ability of the proposed procedure to effectively reduce the computational effort and to reliably design the NES is showed through an application on a well-known case study related to the vibrations mitigation of an aircraft wing.

• Structural Engineering and Mechanics
• /
• v.63 no.6
• /
• pp.789-797
• /
• 2017

Recently, some integrated structural identification/damage detection and reliability evaluation of structures with uncertainties have been proposed. However, these techniques are applicable for off-line synthesis of structural identification and reliability evaluation. In this paper, based on the recursive formulation of the extended Kalman filter, an on-line integration of structural identification/damage detection and reliability evaluation of stochastic building structures is investigated. Structural limit state is expanded by the Taylor series in terms of uncertain variables to obtain the probability density function (PDF). Both structural component reliability with only one limit state function and system reliability with multi-limit state functions are studied. Then, it is extended to adopt the recent extended Kalman filter with unknown input (EKF-UI) proposed by the authors for on-line integration of structural identification/damage detection and structural reliability evaluation of stochastic building structures subject to unknown excitations. Numerical examples are used to demonstrate the proposed method. The evaluated results of structural component reliability and structural system reliability are compared with those by the Monte Carlo simulation to validate the performances of the proposed method.

• Journal of Radiation Protection and Research
• /
• v.16 no.1
• /
• pp.53-72
• /
• 1991

An integrated model is developed in this paper for the performance assessment of high level radioactive waste repository. This integrated model consists of two simple mathematical models. One is a multiple-barrier failure model of the repository system based on constant failure rates which provides source terms to biosphere. The other is a biosphere model which has multiple pathways for radionuclides to reach to human. For the parametric uncertainty and sensitivity analysis for the risk assessment of high level radioactive waste repository, Latin hypercube sampling and rank correlation techniques are applied to this model. The former is cost-effective for large computer programs because it gives smaller error in estimating output distribution even with smaller number of runs compared to crude Monte Carlo technique. The latter is good for generating dependence structure among samples of input parameters. It is also used to find out the most sensitive, or important, parameter groups among given input parameters. The methodology of the mathematical modelling with statistical analysis will provide useful insights to the decision-making of radioactive waste repository selection and future researches related to uncertain and sensitive input parameters.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.11-19
• /
• 2005

First, methods of numerical analysis of gas-particle flows is classified into micro, meso and macro scale approaches based on the concept of multi-scale mechanics. Next, the explanation moves on to discrete particle simulation where motion of individual particles is calculated numerically using the Newtonian equations of motion. The author focuses on the cases where particle-to-particle interaction has significant effects on the phenomena. Concerning the particle-to-particle interaction, two cases are considered: the one is collision-dominated flows and the other is the contact-dominated flows. To treat this interaction mathematically, techniques named DEM(Distinct Element Method) or DSMC (Direct Simulation Monte Carlo) have been developed DEM, which has been developed in the field of soil mechanics, is useful for the contact -dominated flows and DSMC method, developed in molecular gas flows, is for the collision-dominated flows. Combining DEM or DSMC with CFD (computer fluid dynamics), the discrete particle simulation becomes a more practical tool for industrial flows because not only the particle-particle interaction but particle-fluid interaction can be handled. As examples of simulations, various results are shown, such as hopper flows, particle segregation phenomena, particle mixing in a rotating drum, dense phase pneumatic conveying, spouted bed, dense phase fluidized bed, fast circulating fluidized bed and so on.

• Communications for Statistical Applications and Methods
• /
• v.25 no.2
• /
• pp.131-157
• /
• 2018

We propose a robust event date model to estimate the date of a target event by a combination of individual dates obtained from archaeological artifacts assumed to be contemporaneous. These dates are affected by errors of different types: laboratory and calibration curve errors, irreducible errors related to contaminations, and taphonomic disturbances, hence the possible presence of outliers. Modeling based on a hierarchical Bayesian statistical approach provides a simple way to automatically penalize outlying data without having to remove them from the dataset. Prior information on individual irreducible errors is introduced using a uniform shrinkage density with minimal assumptions about Bayesian parameters. We show that the event date model is more robust than models implemented in BCal or OxCal, although it generally yields less precise credibility intervals. The model is extended in the case of stratigraphic sequences that involve several events with temporal order constraints (relative dating), or with duration, hiatus constraints. Calculations are based on Markov chain Monte Carlo (MCMC) numerical techniques and can be performed using ChronoModel software which is freeware, open source and cross-platform. Features of the software are presented in Vibet et al. (ChronoModel v1.5 user's manual, 2016). We finally compare our prior on event dates implemented in the ChronoModel with the prior in BCal and OxCal which involves supplementary parameters defined as boundaries to phases or sequences.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.7
• /
• pp.27-33
• /
• 2013

In this paper, we design and analyze the performance of Coordinated Multi-Point (CoMP) techniques to the number of users for next-generation cellular systems. We perform Monte Carlo simulations with Long Term Evolution-Advanced (LTE-Advanced) and confirm the performance from the graph of the Cumulative Distribution Function (CDF). From simulation results, we show the significant performance gain when CoMP technique is used and also show better performance when we apply the various schemes additionally as scheduling and precoding.