scholarly journals A Study on the Influences of Low-Frequency Vorticity on Tropical Cyclone Formation in the Western North Pacific

2017 ◽  
Vol 145 (10) ◽  
pp. 4151-4169 ◽  
Author(s):  
Yi-Huan Hsieh ◽  
Cheng-Shang Lee ◽  
Chung-Hsiung Sui
Keyword(s):  
Formation Process ◽  
North Pacific ◽  
Western North Pacific ◽  
Wrf Model ◽  
Low Frequency ◽  
Cumulus Parameterization ◽  
Dominant Factor ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Cumulus Scheme

The WRF Model is used to simulate 52 tropical cyclones (TCs) that formed in the western North Pacific during 2008–09 to study the influence of the low-frequency mode of environmental vorticity on TC formation [ Vmax ~ 25 kt (~13 m s−1)]. All simulations, using the same model setting, are repeated at four distinct initial times and with two different initial datasets. These TCs are classified into two groups based on the environmental 850-hPa low-frequency vorticity (using a 10-day low-pass filter) during the period 24–48 h prior to TC formation. Results show that the WRF Model is more capable of simulating the TC formation process, but with larger track errors for TCs formed in an environment with higher low-frequency vorticity (HTC). In contrast, the model is less capable of simulating the TC formation process for TCs formed in an environment with lower low-frequency vorticity (LTC), but with smaller track errors. Fourteen selected TCs are further simulated to examine the sensitivity of previous results to different cumulus parameterization schemes. Results show that the capability of the WRF Model to simulate HTC formation is not sensitive to the choice of cumulus scheme. However, for an LTC, the simulated convection pattern is very sensitive to the cumulus scheme used; therefore, model simulation capability for LTC depends on the cumulus scheme used. Results of this study reveal that the convection process is not a dominant factor in HTC formation, but is very important for LTC formation.

scholarly journals Factors of boreal summer latent heat flux variations over the tropical western North Pacific

2021 ◽  
Author(s):  
Yuqi Wang ◽  
Renguang Wu
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
North Pacific ◽  
High Frequency ◽  
Western North Pacific ◽  
Surface Wind ◽  
Low Frequency ◽  
Boreal Summer ◽  
Wind Intensity ◽  
Tropical Western North Pacific

AbstractSurface latent heat flux (LHF) is an important component in the heat exchange between the ocean and atmosphere over the tropical western North Pacific (WNP). The present study investigates the factors of seasonal mean LHF variations in boreal summer over the tropical WNP. Seasonal mean LHF is separated into two parts that are associated with low-frequency (> 90-day) and high-frequency (≤ 90-day) atmospheric variability, respectively. It is shown that low-frequency LHF variations are attributed to low-frequency surface wind and sea-air humidity difference, whereas high-frequency LHF variations are associated with both low-frequency surface wind speed and high-frequency wind intensity. A series of conceptual cases are constructed using different combinations of low- and high-frequency winds to inspect the respective effects of low-frequency wind and high-frequency wind amplitude to seasonal mean LHF variations. It is illustrated that high-frequency wind fluctuations contribute to seasonal high-frequency LHF only when their intensity exceeds the low-frequency wind speed under which there is seasonal accumulation of high-frequency LHF. When high-frequency wind intensity is smaller than the low-frequency wind speed, seasonal mean high-frequency LHF is negligible. Total seasonal mean LHF anomalies depend on relative contributions of low- and high-frequency atmospheric variations and have weak interannual variance over the tropical WNP due to cancellation of low- and high-frequency LHF anomalies.

scholarly journals Ladder-Based Synthesis and Design of Low-Frequency Buffer-Based CMOS Filters

Electronics ◽  
2021 ◽  
Vol 10 (23) ◽  
pp. 2931
Author(s):  
Waldemar Jendernalik ◽  
Jacek Jakusz ◽  
Grzegorz Blakiewicz
Keyword(s):  
Dynamic Range ◽  
Low Voltage ◽  
Supply Voltage ◽  
Low Frequency ◽  
Cmos Technology ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Biomedical Sensors ◽  
Filter Synthesis ◽  
Cascade Method

Buffer-based CMOS filters are maximally simplified circuits containing as few transistors as possible. Their applications, among others, include nano to micro watt biomedical sensors that process physiological signals of frequencies from 0.01 Hz to about 3 kHz. The order of a buffer-based filter is not greater than two. Hence, to obtain higher-order filters, a cascade of second-order filters is constructed. In this paper, a more general method for buffer-based filter synthesis is developed and presented. The method uses RLC ladder prototypes to obtain filters of arbitrary orders. In addition, a set of novel circuit solutions with ultra-low voltage and power are proposed. The introduced circuits were synthesized and simulated using 180-nm CMOS technology of X-FAB. One of the designed circuits is a fourth-order, low-pass filter that features: 100-Hz passband, 0.4-V supply voltage, power consumption of less than 5 nW, and dynamic range above 60 dB. Moreover, the total capacitance of the proposed filter (31 pF) is 25% lower compared to the structure synthesized using a conventional cascade method (40 pF).

Five-day track forecast skills of WRF model for the western North Pacific tropical cyclones

2021 ◽  
Author(s):  
Jihong Moon ◽  
Jinyoung Park ◽  
Dong-Hyun Cha ◽  
Yumin Moon
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Forecast Error ◽  
Wrf Model ◽  
Analysis Data ◽  
Track Forecast ◽  
Steering Vector ◽  
Group 2 ◽  
Group 1

AbstractIn this study, the characteristics of simulated tropical cyclones (TCs) over the western North Pacific by a regional model (the WRF model) are verified. We utilize 12 km horizontal grid spacing, and simulations are integrated for 5 days from model initialization. One hundred and twenty-five forecasts are divided into five clusters through the k-means clustering method. The TCs in the cluster 1 and 2 (group 1), which includes many TCs moves northward in subtropical region, generally have larger track errors than for TCs in cluster 3 and 4 (group 2). The optimal steering vector is used to examine the difference in the track forecast skill between these two groups. The bias in the steering vector between the model and analysis data is found to be more substantial for group 1 TCs than group 2 TCs. The larger steering vector difference for group 1 TCs indicates that environmental fields tend to be poorly simulated in group 1 TC cases. Furthermore, the residual terms, including the storm-scale process, asymmetric convection distribution, or beta-related effect, are also larger for group 1 TCs than group 2 TCs. Therefore, it is probable that the large track forecast error for group 1 TCs is a result of unreasonable simulations of environmental wind fields and residual processes in the midlatitudes.

scholarly journals Prediction of Favorable Carbonate Reservoirs under Extremely Thick Salts via Poststack Facies-Controlled and Prestack Zoeppritz Equation Inversions in the Santos Basin of Brazil

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Sheng Zhang ◽  
Suoliang Chang ◽  
Handong Huang ◽  
Yinping Dong ◽  
Youyi Shen ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Large Angle ◽  
Low Frequency ◽  
Prediction Method ◽  
Approximate Equation ◽  
Carbonate Reservoirs ◽  
Linear Inversion ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Oil And Gas Exploration

Subsalt carbonate rocks in Brazil’s deepwater region have broad prospects for oil and gas exploration and development. Due to the low-frequency bandwidth of the seismic data and the poor signal quality for this kind of reservoir target, there is a demand for accurate seismic prediction methods. We employ the facies-controlled inversion using a low-pass filter matrix to ensure the accuracy of the low frequency and to improve the robustness of the inversion results. We integrated the concept of adaptive regularization constraint of the Zoeppritz equation into the generalized linear inversion theory framework, which overcomes the shortcomings of the approximate equation. Making full use of the large angle prestack seismic information, Zoeppritz equation inversion improves the accuracy of the inversion results. The application of this method in carbonate reservoirs under extremely thick salts in the Santos Basin of Brazil indicates the feasibility and practicality of the proposed integrated prediction method.

A New Capacitance Multiplier Structure with High Multiplication Factor for Ultra-Low-Frequency Filter in Biomedical Applications

2019 ◽  
Vol 29 (07) ◽  
pp. 2050109
Author(s):  
Yan Li ◽  
Yong Liang Li
Keyword(s):  
Biomedical Applications ◽  
Low Frequency ◽  
Multiplication Factor ◽  
Frequency Filter ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Physiological Signal ◽  
Wide Range ◽  
Low Pass ◽  
Capacitance Multiplier

A novel capacitance multiplier is proposed to implement an ultra-low-frequency filter for physiological signal processing in biomedical applications. With the proposed multiplier, a simple first-order low-pass filter achieves a [Formula: see text]3-dB frequency of 33.4[Formula: see text]μHz with a 1-pF capacitance and a 20[Formula: see text]k[Formula: see text] resistance. This corresponds to a multiplication factor of as large as [Formula: see text]. By changing the controlling terminal, the [Formula: see text]3-dB frequency can be tuned in a wide range of 33.4[Formula: see text]μHz–6.3[Formula: see text]kHz.

Design of the Broadband Standard Signal Generator for Laser Locating System of the Mine Hoisting Container

2013 ◽  
Vol 427-429 ◽  
pp. 2033-2036
Author(s):  
Di Fan ◽  
Yan Gao ◽  
Yue Zhao
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Frequency Standard ◽  
Analog Filters ◽  
Laser Ranging ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Noise Disturbance ◽  
Standard Signal ◽  
Low Pass

As the key junction between the ground and underground, hoisting systems as well as mines themselves are of vital importance to coalmine production. Laser ranging method is studied as a new solution of getting the real-time position directly. Furthermore, multi-scale phase based laser ranging principles are utilized in the system. The paper is aimed to conduct research into the problems existing in standard signal generating while using laser to locating the hoisting container, and to design standard sine generator circuits with DDS technology and DDS devices AD9850 to generate multiple frequency standard signals. In view of the serious noise disturbance in high frequency output, 4-order Chebyshev low-pass filter is designed, by using the integrated analog filters LT 6600-15, to filter the sine signals from AD9850 and to effectively weaken the noise disturbance. The established practical circuits are tested, obtaining trillion level high frequency and low frequency sine signals and fulfilling the requirements for the location system of hoisting containers.

scholarly journals EXPERIMENTAL EVIDENCE FOR VIBRATIONAL RESONANCE AND ENHANCED SIGNAL TRANSMISSION IN CHUA'S CIRCUIT

2013 ◽  
Vol 23 (11) ◽  
pp. 1350189 ◽  
Author(s):  
R. JOTHIMURUGAN ◽  
K. THAMILMARAN ◽  
S. RAJASEKAR ◽  
M. A. F. SANJUÁN
Keyword(s):  
Experimental Evidence ◽  
Low Frequency ◽  
Signal Propagation ◽  
Chua’S Circuit ◽  
Vibrational Resonance ◽  
Frequency Signal ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Chua's Circuit ◽  
Wide Range

We consider a single Chua's circuit and a system of a unidirectionally coupled n-Chua's circuits driven by a biharmonic signal with two widely different frequencies ω and Ω, where Ω ≫ ω. We show experimental evidence for vibrational resonance in the single Chua's circuit and undamped signal propagation of a low-frequency signal in the system of n-coupled Chua's circuits where only the first circuit is driven by the biharmonic signal. In the single circuit, we illustrate the mechanism of vibrational resonance and the influence of the biharmonic signal parameters on the resonance. In the n(=75)-coupled Chua's circuits enhanced propagation of low-frequency signal is found to occur for a wide range of values of the amplitude of the high-frequency input signal and coupling parameter. The response amplitude of the ith circuit increases with i and attains a saturation. Moreover, the unidirectional coupling is found to act as a low-pass filter.

scholarly journals Inductanceless high order low frequency filters for medical applications

2022 ◽  
Vol 12 (2) ◽  
pp. 1299
Author(s):  
Noor Thamer Almalah ◽  
Faris Hasan Aldabbagh
Keyword(s):  
Integrated Circuit ◽  
Low Frequency ◽  
Negative Resistance ◽  
Acceptable Result ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Transconductance Amplifier ◽  
Low Pass ◽  
Minimum Number ◽  
Order Butterworth Filter

<p>In this paper, a designed circuit used for low-frequency filters is implemented and realized the filter is based on frequency-dependent negative resistance (FDNR) as an inductor simulator to substitute the traditional inductance, which is heavy and high cost due to the coil material manufacturing and size area. The simulator is based on an active operation amplifier or operation transconductance amplifier (OTA) that is easy to build in an integrated circuit with a minimum number of components. The third and higher-order Butterworth filter is simulated at low frequency for low pass filter to use in medical instruments and low-frequency applications. The designed circuit is compared with the traditional proportional integral controller enhanced (PIE) and T section ordinary filter. The results with magnitude and phase response were compared and an acceptable result is obtained. The filter can be used for general applications such as medical and other low-frequency filters needed.</p>

TECHNIQUE OF APPLICATION FOR PROCESSING OF LOW PASS FILTER LF SIGNALS

10.12737/7905 ◽  
2015 ◽  
Vol 7 (4) ◽  
pp. 35-38
Author(s):  
Табаков ◽  
Yu. Tabakov ◽  
Лавлинский ◽  
V. Lavlinskiy
Keyword(s):  
Mathematical Model ◽  
Block Diagram ◽  
Low Frequency ◽  
Frequency Signal ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
The Mathematical Model ◽  
40 Hz

The article includes a block diagram and the mathematical model for low pass filter designed for processing low frequency signal with a frequency of 10-40 Hz in order of eliminate various noises and interference.

The influence of the planted geophone on seismic land data

Geophysics ◽  
1980 ◽  
Vol 45 (8) ◽  
pp. 1239-1253 ◽  
Author(s):  
G. M. Hoover ◽  
J. T. O’Brien
Keyword(s):  
Seismic Data ◽  
High Frequency ◽  
Mineral Exploration ◽  
Low Frequency ◽  
Soil Consolidation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Strong Damping ◽  
Local Soil ◽  
Oscillatory Coupling

Characteristics of the seismic data acquisition system that previously have been ignored become important as more sophisticated interpretive methods based on broader frequency bandwidths are developed to extract stratigraphic information from land data in hydrocarbon and mineral exploration. Theoretical and experimental results indicate that the geophone plant can be approximated by a damped oscillatory coupling, properties dependent upon the geophone mass, dimension of earth contact, and local soil consolidation. A massive geophone with minimal earth contact exhibits a low‐frequency plant resonance with weak damping and acts as a low‐pass filter to eliminate the high‐frequency components of a recorded signal. A lightweight geophone with large earth contact exhibits a high‐frequency plant resonance with strong damping and, consequently, filtering effects are minimal if the plant resonance is well above the signal bandwidth. Although signal filtering influences are weak for strong damping, phase delays can introduce errors of several milliseconds which resemble static errors. Additional complications arise since these time shifts are frequency dependent and, consequently, not identical for all reflection events in a seismic trace. The resonant frequency of the geophone plant increases with increased soil consolidation; however, damping demonstrates only a weak dependence upon consolidation. All of these factors can limit the effectiveness of common‐depth‐point (CDP) stacking methods if the proper technique is not practiced in the acquisition of broad‐bandwidth seismic data.

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