17,032 research outputs found
Aiding fault diagnosis under symptom masking in dynamic systems
No full textIn large-scale dynamic systems such as power plants, fault diagnosis becomes more difficult owing to changing system states. Symptoms can be obscured by other symptoms or disappear as the operator proceeds with diagnosis or compensation. Such a symptom-masking phenomenon increases the operator's memory load, constrains diagnostic strategies and, hence, degrades the performance of the diagnosis. This study investigates the effects of a symptom-bookkeeping aid (SB-aid) for diagnostic performance in a simulated sub-system of nuclear power plants. The results show that this SE-aid improved overall performance. Further analyses provide insights on the sources of cognitive difficulties and on the possible direction of supporting human diagnosis in dynamic plants.This research was supported by Korea Electric Power Research Institute (KEPRI )
Reconstruction of aeroacoustic source strength distributions by inverse techniques
No full textAn investigation is presented of the reconstruction of aeroacoustic source strength distributions by inverse techniques based on the least squares method. The essence of the discrete inverse problem enabling the source strength reconstruction is the conditioning of the matrix to be inverted. A study is made of the behaviour of the condition number associated with the matrix of radiation transfer functions of each of three elemental acoustic source types. In order to enhance the accuracy of reconstruction, methods such as Tikhonov regularisation and singular value discarding are applied. A description is also given of methods for choosing the regularisation parameter and the singular values to be discarded by using the generalised cross-validation technique. It is concluded that aeroacoustic source strength distributions can be reconstructed with reasonably acceptable accuracy if we choose a good geometrical arrangement of microphone array together with an appropriate choice of the regularisation parameter and the singular values to be discarded.</p
Photosensitized diastereoisomer-specific degradation of hexabromocyclododecane (HBCD) in the presence of humic acid in aquatic systems
No full textHumic acids (HA) are the most important photosensitizers in the ocean and generate highly reactive oxygen species (ROS), known as photochemically produce reactive intermediates (PPRI), which degrade organic pollutants. Thus, to reveal the fate of organic pollutants in an aqueous environment, it is important to understand the natural photodegradation phenomenon caused by HA. Three ROS generated from HA, O-1(2), O2- and (OH)-O-center dot, were measured using different probe compounds and instrumental techniques. In this study, HBCD (hexabromocyclododecane), a newly listed one of persistent organic pollutants (POPs) under the Stockholm Convention, was studied to understand the phototransformation mechanism, which has not been sufficiently investigated in terms of its environmental fate and transport, despite the distinctive features of its diastereoisomers. The results showed that the diastereoisomer-specific distributions of alpha-, beta-, and gamma-HBCD were related to the acceleration and retardation of photodegradation in the presence of AHA (Aldrich Humic Acid) under simulated solar light, and only alpha-HBCD was rapidly photodegraded as the amount of AHA increased relative to the absence of AHA. This study provides the first characterization of the behavior of photosensitized HBCD degradation in aquatic systems.11Nsciescopu
Reduction of Process Variations for Sub-5-nm Node Fin and Nanosheet FETs Using Novel Process Scheme
No full textProcess (systematic) variations of sub-5-nm node fin field-effect transistors (FinFETs) and nanosheet field-effect transistors (NSFETs) were investigated thoroughly using fully calibrated TCAD. All the process parameters consisting of front-end-as well as middle-of-line structure were independently randomized within feasible process conditions. A novel process scheme called source/drain patterning (SDP), having a superior performance by decreasing outer fringing capacitance through the downsized source/drain (S/D) epi, has also been analyzed for the variability study. SDP FinFETs have smaller variations of threshold voltages (V-th), OFF-state currents (I-OFF), and effective currents (I-eff) than conventional ones because the subfin leakage is effectively controlled by bottom oxide (BO) beneath the source/drain instead of high punchthrough-stopper doping. The Spearman's correlation results between process parameters, I-OFF, and I-eff, showed that the process parameters affecting the short-channel effects vary I-OFF and I-eff greatly. Especially, the most critical one was the fin width (W-fin) for FinFETs. SDP NSFETs have the smallest variations of V-th, I-OFF, and I-eff. The BO blocks the bottom leakage completely, and the variations of nanosheet (NS) thickness(T-NS) aremuchsmaller than those of W-fin due to the different process flows: epitaxial growth for T-NS versus patterning for W-fin. Therefore, NSFETs are promising to reduce the variations of V-th, I-OFF, and I-eff in the sub-5-nm node.11Nsciescopu
Expression profile analysis of metabolism of Escherichia coli during high cell density cultivation usng DNA chip
No full textTreatability of hexabromocyclododecane using Pd/Fe nanoparticles in the soil-plant system: Effects of humic acids
No full textHexabromocyclododecane (HBCD) is a persistent organic pollutant that accumulates in soil and sediments, however, it has been difficult to degrade HBCD with developed remediation technologies so far. In this study, degradation of HBCD by bimetallic iron-based nanoparticles (NPs) under both aqueous and soil conditions considering the effects of humic acids (HAs) and tobacco plant was investigated. In the aqueous solution, 99% of the total HBCD (15 mM) was transformed by Pd/nFe (1 g L-1) within 9 h of treatment and the HBCD debromination by Pd/nFe increased with the addition of HAs. In the soil system, 13%, 15%, 41% and 27% of the total HBCD were removed by treatments consisting of plant only, plant with HAs, plant with NPs and plant + NPs + HAs, respectively, compared to the HBCD removal in an unplanted soil. The 221-986 ng/g of HBCD were detected inside the plant after the treatments, and HAs showed considerable influence on the selective bioaccumulation of HBCD stereoisomers in the plant. Overall, this approach represents a meaningful attempt to develop an efficient and eco-friendly technology for HBCD removal, and it provides advantages for the sustainable remediation of recalcitrant emerging contaminants in soils. (C) 2019 Elsevier B.V. All tights reserved.11Nsciescopu
Interlaminar fracture toughness of graphite/epoxy composite under mixed-mode deformations
No full textAdaptive resource reservation for efficient resource utilization in the wireless multimedia network
No full textOutput Regulation of Linear Aperiodic Sampled-Data Systems
No full textThis paper deals with the output regulation problem of a linear time-invariant system in the presence of sporadically available measurement streams. A regulator with a continuous intersample injection term is proposed, where the intersample injection is provided by a linear dynamical system and the state of which is reset with the arrival of every new measurement updates. The resulting system is augmented with a timer triggering an instantaneous update of the new measurement and the overall system is then analyzed in a hybrid system framework. With the Lyapunov based stability analysis, we offer sufficient conditions to ensure the objectives of the output regulation problem are achieved under intermittency of the measurement streams. Then, from the solution to linear matrix inequalities, a numerically tractable regulator design procedure is presented. Finally, with the help of an illustrative example, the effectiveness of the theoretical results are validated
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