Managing Nonrandomly Varying Fisheries

Theoretical studies indicate that constant effort or constant escapement harvest strategies are viable long-term management policies for fisheries influenced by random environmental variability. But the marine environment and fishery recruitment do not characteristically vary randomly: their time series tend to be autocorrelated. I examined the response of a model of an age-structured fish population to these harvest strategies, if recruitment is influenced by periodic variability. Variance in fish yield and the incidence of low stock size increased with both increasing amplitude and period length of environmental forcing. Sensitivity to environmental fluctuations increased sharply at periodicities between one and several times the generation length. Low-risk fisheries, which are subject to little nonrandom recruitment variability, may be satisfactorily managed by either management strategy, although constant effort harvesting provided greater stability to industry with little risk to the fish population. Neither strategy maintained stability in high-risk fisheries with high-amplitude, low-frequency recruitment variability, but a constant escapement policy minimized risk of stock collapse.

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Electrical Resistive Spiking of Fungi

Biophysical Reviews and Letters ◽

10.1142/s1793048021500016 ◽

2021 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Andrew Adamatzky ◽

Alessandro Chiolerio ◽

Georgios Sirakoulis

Keyword(s):

Electrical Resistance ◽

Electronic Devices ◽

Low Frequency ◽

High Amplitude ◽

Average Amplitude ◽

Average Width ◽

C 23 ◽

C 30 ◽

Low Amplitude

We study long-term electrical resistance dynamics in mycelium and fruit bodies of oyster fungi P. ostreatus. A nearly homogeneous sheet of mycelium on the surface of a growth substrate exhibits trains of resistance spikes. The average width of spikes is c. 23[Formula: see text]min and the average amplitude is c. 1[Formula: see text]k[Formula: see text]. The distance between neighboring spikes in a train of spikes is c. 30[Formula: see text]min. Typically, there are 4–6 spikes in a train of spikes. Two types of electrical resistance spikes trains are found in fruit bodies: low frequency and high amplitude (28[Formula: see text]min spike width, 1.6[Formula: see text]k[Formula: see text] amplitude, 57[Formula: see text]min distance between spikes) and high frequency and low amplitude (10[Formula: see text]min width, 0.6[Formula: see text]k[Formula: see text] amplitude, 44[Formula: see text]min distance between spikes). The findings could be applied in monitoring of physiological states of fungi and future development of living electronic devices and sensors.

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On the Procedure of Draught Rate Assessment in Indoor Spaces

Applied Sciences ◽

10.3390/app10155036 ◽

2020 ◽

Vol 10 (15) ◽

pp. 5036

Author(s):

Detelin Markov ◽

Nikolay Ivanov ◽

George Pichurov ◽

Marina Zasimova ◽

Peter Stankov ◽

...

Keyword(s):

Thermal Environment ◽

Low Frequency ◽

High Amplitude ◽

Time Interval ◽

Cfd Simulations ◽

Reliable Assessment ◽

Unsteady Rans ◽

Computational Fluid Dynamics Cfd ◽

Indoor Spaces

The objective of the paper is to demonstrate the importance of the unsteady Computational Fluid Dynamics (CFD) simulations and long-term measurements for the reliable assessment of thermal comfort indoors, for proper categorization of the indoor thermal environment and for identifying the reasons for complaints due to draught discomfort. Numerical simulations and experimental measurements were applied in combination to study ventilation in a field laboratory, a university classroom with a controlled indoor environment. Strong unsteadiness of the airflow was registered both in the unsteady RANS results and the real-scale long-term velocity data measured with thermo anemometer. Low-frequency high-amplitude velocity fluctuations observed lead to substantial time variation of the draught rate. In case of categorization of a thermal environment, the point measurements or steady-state RANS computations would lead to wrong conclusions as well as they cannot be used for identification of the reasons for people’s complaints due to draught discomfort if strong unsteadiness of the airflow exists. It is demonstrated that the length of the time interval for draught rate (DR) assessment may not be universal if low-frequency high-amplitude pulsations are present in the room airflow.

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APPLICATION OF THE EMPIRICAL MODE DECOMPOSITION METHOD TO GROUND-ROLL NOISE ATTENUATION IN SEISMIC DATA

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v31i4.342 ◽

2013 ◽

Vol 31 (4) ◽

pp. 619 ◽

Cited By ~ 1

Author(s):

Luiz Eduardo Soares Ferreira ◽

Milton José Porsani ◽

Michelângelo G. Da Silva ◽

Giovani Lopes Vasconcelos

Keyword(s):

Empirical Mode Decomposition ◽

Seismic Data ◽

Low Frequency ◽

High Amplitude ◽

Seismic Line ◽

Seismic Processing ◽

Mode Decomposition ◽

Ground Roll ◽

Fortran 90 ◽

Emd Method

ABSTRACT. Seismic processing aims to provide an adequate image of the subsurface geology. During seismic processing, the filtering of signals considered noise is of utmost importance. Among these signals is the surface rolling noise, better known as ground-roll. Ground-roll occurs mainly in land seismic data, masking reflections, and this roll has the following main features: high amplitude, low frequency and low speed. The attenuation of this noise is generally performed through so-called conventional methods using 1-D or 2-D frequency filters in the fk domain. This study uses the empirical mode decomposition (EMD) method for ground-roll attenuation. The EMD method was implemented in the programming language FORTRAN 90 and applied in the time and frequency domains. The application of this method to the processing of land seismic line 204-RL-247 in Tacutu Basin resulted in stacked seismic sections that were of similar or sometimes better quality compared with those obtained using the fk and high-pass filtering methods.Keywords: seismic processing, empirical mode decomposition, seismic data filtering, ground-roll. RESUMO. O processamento sísmico tem como principal objetivo fornecer uma imagem adequada da geologia da subsuperfície. Nas etapas do processamento sísmico a filtragem de sinais considerados como ruídos é de fundamental importância. Dentre esses ruídos encontramos o ruído de rolamento superficial, mais conhecido como ground-roll . O ground-roll ocorre principalmente em dados sísmicos terrestres, mascarando as reflexões e possui como principais características: alta amplitude, baixa frequência e baixa velocidade. A atenuação desse ruído é geralmente realizada através de métodos de filtragem ditos convencionais, que utilizam filtros de frequência 1D ou filtro 2D no domínio fk. Este trabalho utiliza o método de Decomposição em Modos Empíricos (DME) para a atenuação do ground-roll. O método DME foi implementado em linguagem de programação FORTRAN 90, e foi aplicado no domínio do tempo e da frequência. Sua aplicação no processamento da linha sísmica terrestre 204-RL-247 da Bacia do Tacutu gerou como resultados, seções sísmicas empilhadas de qualidade semelhante e por vezes melhor, quando comparadas as obtidas com os métodos de filtragem fk e passa-alta.Palavras-chave: processamento sísmico, decomposição em modos empíricos, filtragem dados sísmicos, atenuação do ground-roll.

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Long Term Effects of Low Frequency (10 Hz) Vagus Nerve Stimulation on EEG and Heart Rate Variability in Crohn's Disease: A Case Report

Brain Stimulation ◽

10.1016/j.brs.2014.08.001 ◽

2014 ◽

Vol 7 (6) ◽

pp. 914-916 ◽

Cited By ~ 26

Author(s):

Didier Clarençon ◽

Sonia Pellissier ◽

Valérie Sinniger ◽

Astrid Kibleur ◽

Dominique Hoffman ◽

...

Keyword(s):

Heart Rate ◽

Heart Rate Variability ◽

Crohn’S Disease ◽

Case Report ◽

Vagus Nerve ◽

Nerve Stimulation ◽

Vagus Nerve Stimulation ◽

Low Frequency ◽

Long Term Effects

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Induction of long-term potentiation without participation of N-methyl-D-aspartate receptors in kitten visual cortex

Journal of Neurophysiology ◽

10.1152/jn.1991.65.1.20 ◽

1991 ◽

Vol 65 (1) ◽

pp. 20-32 ◽

Cited By ~ 47

Author(s):

Y. Komatsu ◽

S. Nakajima ◽

K. Toyama

Keyword(s):

Nmda Receptors ◽

Stimulus Frequency ◽

Low Frequency ◽

Nmda Antagonist ◽

Long Term Potentiation ◽

Conditioning Stimulation ◽

Postsynaptic Potential ◽

Term Potentiation ◽

Stimulation Of

1. Intracellular recording was made from layer II-III cells in slice preparations of kitten (30-40 days old) visual cortex. Low-frequency (0.1 Hz) stimulation of white matter (WM) usually evoked an excitatory postsynaptic potential (EPSP) followed by an inhibitory postsynaptic potential (IPSP). The postsynaptic potentials (PSPs) showed strong dependence on stimulus frequency. Early component of EPSP and IPSP evoked by weak stimulation both decreased monotonically at frequencies greater than 0.5-1 Hz. Strong stimulation similarly depressed the early EPSP at higher frequencies (greater than 2 Hz) and replaced the IPSP with a late EPSP, which had a maximum amplitude in the stimulus frequency range of 2-5 Hz. 2. Very weak WM stimulation sometimes evoked EPSPs in isolation from IPSPs. The falling phase of the EPSP revealed voltage dependence characteristic to the responses mediated by N-methyl-D-aspartate (NMDA) receptors and was depressed by application of an NMDA antagonist DL-2-amino-5-phosphonovalerate (APV), whereas the rising phase of the EPSP was insensitive to APV. 3. The early EPSPs followed by IPSPs were insensitive to APV but were replaced with a slow depolarizing potential by application of a non-NMDA antagonist 6,7-dinitro-quinoxaline-2,3-dione (DNQX), indicating that the early EPSP is mediated by non-NMDA receptors. The slow depolarization was mediated by NMDA receptors because it was depressed by membrane hyperpolarization or addition of APV. 4. The late EPSP evoked by higher-frequency stimulation was abolished by APV, indicating that it is mediated by NMDA receptors, which are located either on the recorded cell or on presynaptic cells to the recorded cells. 5. Long-term potentiation (LTP) of EPSPs was examined in cells perfused with solutions containing 1 microM bicuculline methiodide (BIM), a gamma-aminobutyric acid (GABA) antagonist. WM was stimulated at 2 Hz for 15 min as a conditioning stimulus to induce LTP, and the resultant changes were tested by low-frequency (0.1 Hz) stimulation of WM. 6. LTP of early EPSPs occurred in more than one-half of the cells (8/13) after strong conditioning stimulation. The rising slope of the EPSP was increased 1.6 times on average. 7. To test involvement of NMDA receptors in the induction of LTP in the early EPSP, the effect of conditioning stimulation was studied in a solution containing 100 microM APV, which was sufficient to block completely synaptic transmission mediated by NMDA receptors. LTP occurred in the same frequency and magnitude as in control solution.

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A Chronology of El Niño Events from Primary Documentary Sources in Northern Peru*

Journal of Climate ◽

10.1175/2007jcli1830.1 ◽

2008 ◽

Vol 21 (9) ◽

pp. 1948-1962 ◽

Cited By ~ 53

Author(s):

R. Garcia-Herrera ◽

D. Barriopedro ◽

E. Hernández ◽

H. F. Diaz ◽

R. R. Garcia ◽

...

Keyword(s):

El Niño ◽

El Nino ◽

Southern Oscillation ◽

Low Frequency ◽

Primary Sources ◽

Proxy Data ◽

Documentary Sources ◽

Low Frequency Variability ◽

Northern Peru

Abstract The authors present a chronology of El Niño (EN) events based on documentary records from northern Peru. The chronology, which covers the period 1550–1900, is constructed mainly from primary sources from the city of Trujillo (Peru), the Archivo General de Indias in Seville (Spain), and the Archivo General de la Nación in Lima (Peru), supplemented by a reassessment of documentary evidence included in previously published literature. The archive in Trujillo has never been systematically evaluated for information related to the occurrence of El Niño–Southern Oscillation (ENSO). Abundant rainfall and river discharge correlate well with EN events in the area around Trujillo, which is very dry during most other years. Thus, rain and flooding descriptors, together with reports of failure of the local fishery, are the main indicators of EN occurrence that the authors have searched for in the documents. A total of 59 EN years are identified in this work. This chronology is compared with the two main previous documentary EN chronologies and with ENSO indicators derived from proxy data other than documentary sources. Overall, the seventeenth century appears to be the least active EN period, while the 1620s, 1720s, 1810s, and 1870s are the most active decades. The results herein reveal long-term fluctuations in warm ENSO activity that compare reasonably well with low-frequency variability deduced from other proxy data.

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A Review of Crack Detection In-Line Inspection Case Studies

2010 8th International Pipeline Conference, Volume 1 ◽

10.1115/ipc2010-31114 ◽

2010 ◽

Cited By ~ 2

Author(s):

Neil Bates ◽

David Lee ◽

Clifford Maier

Keyword(s):

Crack Growth ◽

Case Studies ◽

Crack Detection ◽

Growth Parameters ◽

Probability Distributions ◽

Low Frequency ◽

Probability Of Failure ◽

Probability Of Detection ◽

Inspection Data

This paper describes case studies involving crack detection in-line inspections and fitness for service assessments that were performed based on the inspection data. The assessments were used to evaluate the immediate integrity of the pipeline based on the reported features and the long-term integrity of the pipeline based on excavation data and probabilistic SCC and fatigue crack growth simulations. Two different case studies are analyzed, which illustrate how the data from an ultrasonic crack tool inspection was used to assess threats such as low frequency electrical resistance weld seam defects and stress corrosion cracking. Specific issues, such as probability of detection/identification and the length/depth accuracy of the tool, were evaluated to determine the suitability of the tool to accurately classify and size different types of defects. The long term assessment is based on the Monte Carlo method [1], where the material properties, pipeline details, crack growth parameters, and feature dimensions are randomly selected from certain specified probability distributions to determine the probability of failure versus time for the pipeline segment. The distributions of unreported crack-related features from the excavation program are used to distribute unreported features along the pipeline. Simulated crack growth by fatigue, SCC, or a combination of the two is performed until failure by either leak or rupture is predicted. The probability of failure calculation is performed through a number of crack growth simulations for each of the reported and unreported features and tallying their respective remaining lives. The results of the probabilistic analysis were used to determine the most effective and economical means of remediation by identifying areas or crack mechanisms that contribute most to the probability of failure.

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Frequency Response Analysis of Piecewise Nonlinear Vibration Isolator

Volume 1: 20th Biennial Conference on Mechanical Vibration and Noise, Parts A, B, and C ◽

10.1115/detc2005-84879 ◽

2005 ◽

Cited By ~ 2

Author(s):

Patrick Stahl ◽

G. Nakhaie Jazar

Keyword(s):

Low Frequency ◽

High Amplitude ◽

Relative Displacement ◽

Response Analysis ◽

Frequency Response Analysis ◽

State Behavior ◽

Vibration Isolators ◽

Short Period ◽

Secondary Suspension ◽

Low Amplitude

Non-smooth piecewise functional isolators are smart passive vibration isolators that can provide effective isolation for high frequency/low amplitude excitation by introducing a soft primary suspension, and by preventing a high relative displacement in low frequency/high amplitude excitation by introducing a relatively damped secondary suspension. In this investigation a linear secondary suspension is attached to a nonlinear primary suspension. The primary is assumed to be nonlinear to model the inherent nonlinearities involved in real suspensions. However, the secondary suspension comes into action only during a short period of time, and in mall domain around resonance. Therefore, a linear assumption for the secondary suspension is reasonable. The dynamic behavior of the system subject to a harmonic base excitation has been analyzed utilizing the analytic results derived by applying the averaging method. The analytic results match very well in the transition between the two suspensions. A sensitivity analysis has shown the effect of varying dynamic parameters in the steady state behavior of the system.

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