Structural parameters optimization of a comb-like structure using locally resonant phononic crystals

2019 ◽  
Vol 33 (26) ◽  
pp. 1950312 ◽  
Author(s):  
Hongfeng Zhai ◽  
Hang Xiang ◽  
Xingfu Ma ◽  
Jiawei Xiang
Keyword(s):  
Structural Parameters ◽  
Phononic Crystal ◽  
Low Frequency ◽  
Parameters Optimization ◽  
Functional Relationships ◽  
Elastic Beams ◽  
Surface Method ◽  
Two Factors ◽  
Relationship Of ◽  
The Relationship

In this paper, a comb-like locally resonant phononic crystal (LRPC) with optimal structural parameters, which has good low frequency and broadband band gaps (BGs) between 20–250 Hz, is investigated numerically. With the intention of obtaining the optimal structural parameters, based on the structures with different number of the short elastic beams, 2-factor (the two key structural parameters, i.e. the width of the scatterer and the thickness of elastic beams) and 7-level numerical experiments are designed to obtain simulations data using finite element method (FEM). The functional relationships are further constructed using the response surface method (RSM) analysis, i.e. the relationship of the starting frequency of the first BG and the two factors, the terminating frequency of the second BG and the two factors, and the relationship of the total bandwidth of the first two BG and the two factors. After calculation using interior point method, the BGs of LRPC with optimal structural parameters are determined with lower and wider BGs below 250 Hz.

Optimal bandgaps of a spiral structure based on locally resonant phononic crystals

2019 ◽  
Vol 33 (22) ◽  
pp. 1950256 ◽  
Author(s):  
Hongfeng Zhai ◽  
Hang Xiang ◽  
Xingfu Ma ◽  
Jiawei Xiang
Keyword(s):  
Interior Point Method ◽  
Numerical Experiments ◽  
Spiral Structure ◽  
Phononic Crystal ◽  
Low Frequency ◽  
Side Length ◽  
Elastic Beams ◽  
Two Factors ◽  
Single Factor Analysis ◽  
The Relationship

A spiral locally resonant phononic crystal (LRPC) with the optimal bandgaps (BGs) between 20 and 250 Hz is proposed. The single factor analysis of three key geometric parameters (the thickness of spiral elastic beams, the side length of square scatterers and the spirals’ turns) are performed to obtain corresponding influences on BGs, two-factor (the thickness of spiral elastic beams and the side length of the square scatterer) and seven-level experiment under the four fixed spirals’ turns are designed to obtain optimal BGs with better low-frequency broadband properties. According to numerical experiments, BG data of present spiral LRPCs can be calculated by finite element method (FEM). Relationships (i.e., the relationship between the starting frequency of the first BG and the two factors, the relationship between the bandwidth of the first BG and the two factors, and the relationship between the bandwidth of the second BG and the two factors) are further obtained using the response surface methodology (RSM). The optimal BGs with better properties are finally calculated using the interior point method.

scholarly journals Tunable Low Frequency Band Gap and Waveguide of Phononic Crystal Plates with Different Filling Ratio

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 828
Author(s):  
Shaobo Zhang ◽  
Jiang Liu ◽  
Hongbo Zhang ◽  
Shuliang Wang
Keyword(s):  
Band Gap ◽  
Composite Structure ◽  
Structural Parameters ◽  
Phononic Crystal ◽  
Low Frequency ◽  
Filling Ratio ◽  
Height Ratio ◽  
Road Vehicles ◽  
Aluminum Base ◽  
Gap Width

Aiming at solving the NVH problem in vehicles, a novel composite structure is proposed. The new structure uses a hollow-stub phononic-crystal with filled cylinders (HPFC) plate. Any unit in the plate consists of a lead head, a silicon rubber body, an aluminum base as outer column and an opposite arranged inner pole. The dispersion curves are investigated by numerical simulations and the influences of structural parameters are discussed, including traditional hollow radius, thickness, height ratio, and the new proposed filling ratio. Three new arrays are created and their spectrum maps are calculated. In the dispersion simulation results, new branches are observed. The new branches would move towards lower frequency zone and the band gap width enlarges as the filling ratio decreases. The transmission spectrum results show that the new design can realize three different multiplexing arrays for waveguides and also extend the locally resonant sonic band gap. In summary, the proposed HPFC structure could meet the requirement for noise guiding and filtering. Compared to a traditional phononic crystal plate, this new composite structure may be more suitable for noise reduction in rail or road vehicles.

The relationship of low-frequency deep variability near the HEBBLE site to Gulf Stream fluctuations

1991 ◽  
Vol 99 (3-4) ◽  
pp. 303-317 ◽  
Author(s):  
Elizabeth B Welsh ◽  
Nelson G Hogg ◽  
Ross M Hendry
Keyword(s):  
Gulf Stream ◽  
Low Frequency ◽  
Relationship Of ◽  
The Relationship

Reliance on Visual Imagery and its Relation to Mental Rotation

1997 ◽  
Vol 85 (2) ◽  
pp. 431-434 ◽  
Author(s):  
Doris C. Weatherly ◽  
Steven E. Ball ◽  
James R. Stacks
Keyword(s):  
Mental Rotation ◽  
Response Latency ◽  
High Frequency ◽  
Visual Imagery ◽  
Learning Effect ◽  
Low Frequency ◽  
Computer Screen ◽  
The Right ◽  
Relationship Of ◽  
The Relationship

The relationship of habitual use of visual imagery and mental rotation was investigated. Reliance on Visual Imagery scores were used to define subjects as high frequency or low frequency visualizers. During the mental rotation task, subjects indicated if a pair of 2-dimensional stimulus figures displayed on a computer screen were identical or mirror-images. Figures on the right were rotated in relation to those on the left by 0, 60, 120, or 180°. Data supported the prediction that subjects who report high use of imagery would perform the task with greater accuracy ( z=1.97, p<.05) than subjects who reported low use. The imagery groups did not differ in response latency ( z = .91, p<.36). A comparison of performance on Trials 1 to 24 with performance on Trials 115-138 indicated a learning effect in both accuracy ( z = 7.58, p<.01) and latency ( z = 9.72, p<.01) for all subjects.

Biological Model of Fisheries Production Based on Physiological and Ecological Scalings of Body Size

1989 ◽  
Vol 46 (4) ◽  
pp. 614-623 ◽  
Author(s):  
P. R. Boudreau ◽  
L. M. Dickie
Keyword(s):  
Body Size ◽  
Individual Species ◽  
Data Series ◽  
Biomass Density ◽  
Fish Stocks ◽  
Population Sampling ◽  
Functional Relationships ◽  
Relationship Of ◽  
The Relationship ◽  
Population Equilibrium

Earlier ecological studies showing regularity in the relationship of certain indices of production to body size are used to develop a predictive equation of fish production on a year to year basis, with biomass and body size as independent stock variables. The prediction system makes use of the observed regular adjustments of local biomass density with body size and the parallelism of the functional relationships of production and biomass with body size both between and within stock cohorts. The method obviates the need to invoke assumptions of population equilibrium. The model is applied to three data series for individual species exploited by commercial fisheries on the Scotian Shelf. The results suggest that despite the vagaries of population sampling, ecological information can provide practical estimates of the production potential of fish stocks.

Harmonic and transient fields on the surface of a two‐layer medium

Geophysics ◽  
1979 ◽  
Vol 44 (7) ◽  
pp. 1208-1217 ◽  
Author(s):  
Alexander A. Kaufman
Keyword(s):  
Low Frequency ◽  
Vertical Axis ◽  
Fractional Powers ◽  
Circular Loop ◽  
Ore Body ◽  
Layer Medium ◽  
Relationship Of ◽  
The Relationship ◽  
Finite Extent ◽  
Depth Of Investigation

The article deals with the behavior of the quasi‐static electromagnetic (EM) fields created by currents in a two‐layer medium when the source is a vertical axis circular loop. This analysis is of use for determining the depth of investigation of induction methods in mining prospecting. The relationship of the active and reactive components of the field with the geoelectrical parameters is different, depending on the range of frequencies. Unlike the case of a confined body, the low‐frequency part of the spectrum is presented as a series made up of integral and fractional powers of frequency ω and also logarithmic terms of ω. The late stage of a transient process is described with a sum of terms, proportional to the inverse power of time t. These representations are useful for determining the host rock effect against which the signal from an ore body of finite extent must be detected.

A Kinematic Profile of Skills in Professional Basketball Players

1994 ◽  
Vol 10 (3) ◽  
pp. 205-221 ◽  
Author(s):  
Irene S. McClay ◽  
John R. Robinson ◽  
Thomas P. Andriacchi ◽  
Edward C. Frederick ◽  
Ted Gross ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Knee Flexion ◽  
Structural Parameters ◽  
Overuse Injuries ◽  
Ankle Sprains ◽  
Basketball Players ◽  
Professional Basketball ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Overuse injuries are common in basketball. To gain insight into their etiology and relationship to mechanics, researchers and clinicians need an understanding of the normal biomechanics of the sport. This study was undertaken with this goal in mind. Lower extremity joint kinematics and structural parameters were collected from 24 players from five professional basketball teams as they performed maneuvers typical of their sport. The results indicated that certain common moves such as the layup landing resulted in knee flexion velocities almost double those seen during the landing phase of running. Lateral movements such as cutting and shuffling placed the foot in extreme positions of supination. Both of these findings have implications for injuries common to basketball such as patellar tendinitis and ankle sprains. It is hoped that this information will initiate a database for normal lower extremity kinematics during basketball and lead to a greater understanding of the relationship of lower extremity movement patterns and injury.

scholarly journals NUMERICAL STUDY ON EFFECTS OF TENON SIZES ON WITHDRAWAL LOAD CAPACITY OF MORTISE AND TENON JOINT

Wood Research ◽  
2021 ◽  
Vol 66 (2) ◽  
pp. 321-330
Author(s):  
Tianxing Zhang ◽  
Wengang Hu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Response Surface ◽  
Numerical Study ◽  
Load Capacity ◽  
The Finite Element Method ◽  
Surface Method ◽  
Mortise And Tenon ◽  
Relationship Of ◽  
The Relationship

The effect of tenon length and tenon width on withdrawal load capacity of mortise and tenon (M-T) joint was studied based on the finite element method (FEM), and the relationship of withdrawal load capacity relating to tenon length and tenon width was regressed using response surface method. The results showed that the tenon length and tenon width had remarkable effects on withdrawal load capacity of M-T joint T-shaped sample. The effect of tenon length on withdrawal load capacity was greater than tenon width. The regression equation used to predict the withdrawal load capacity was capable of optimizing the tenon sizes of M-T joint with R-square of 0.926. Using FEM can get more knowledge of M-T joint visually, and reduce the costs of materials and time of experiments.

An integrated approach for prioritizing lean and agile production factors based on costs of quality with a case study in the home appliance industry

2018 ◽  
Vol 25 (2) ◽  
pp. 660-676 ◽  
Author(s):  
Arash Shahin ◽  
Marzieh Rezaei
Keyword(s):  
Production Management ◽  
Strong Relationship ◽  
Integrated Approach ◽  
Quadrant Analysis ◽  
Content Type ◽  
Two Factors ◽  
Home Appliance ◽  
Relationship Of ◽  
The Relationship ◽  
Agile Production

Purpose The purpose of this paper is to prioritize lean production (LP) and agile production (AP) factors based on costs of quality (COQ). Design/methodology/approach After literature review, two separated houses of quality (HoQ) have been developed. By the first HoQ, LP and AP factors can be proritized based on prevention and appraisal costs and by the second HoQ, LP and AP factors can be prioritized based on failure costs. The proposed approach has been examined by analyzing data collected from 36 home appliance producers of Isfahan as an industrial province of Iran. Findings The first HoQ indicates that the highest and the lowest priorities are related to over-production (lean factor) and speed (agility factor), respectively. The second HoQ implies that the highest and the lowest priorities are related to responsiveness (agility factor) and inventory (lean factor), respectively. Quadrant analysis also indicates that defectives and over-processing are the two factors that have the highest priorities based on both failure costs and appraisal and prevention costs. As a major finding, LP factors have strong relationship with prevention and appraisal costs; and AP factors have strong relationship with failure costs. Practical implications The proposed approach helps organizations in reducing their costs. By clarifying the relationship of the LP and AP factors and the COQ, managers can determine appropriate strategies with the lowest cost. Originality/value The integrated approach of this study has not been applied and studied in the literature. The subject of the relationship of LP and AP and COQ is relatively new, which integrates the two areas of production management and quality management.

scholarly journals Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: energy-reflectivity spectrum

2008 ◽  
Vol 26 (7) ◽  
pp. 1793-1803 ◽  
Author(s):  
A. R. Jacobson ◽  
R. Holzworth ◽  
X.-M. Shao
Keyword(s):  
Lightning Discharge ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Angle Of Incidence ◽  
Radio Emissions ◽  
Statistical Variation ◽  
Reflection Height ◽  
D Region ◽  
Relationship Of ◽  
The Relationship

Abstract. We analyze data on radio-reflection from the D-region of the lower ionosphere, retrieving the energy-reflection coefficient in the frequency range ~5–95 kHz. The data are the same as developed for a recent study of ionospheric-reflection height, and are based on recordings of powerful (multi-Gigawatt) radio emissions from a type of narrow (~10 μs) lightning discharge known as "Narrow Bipolar Events". The sequential appearance of first the groundwave signal, and then the ionospheric single-hop reflection signal, permits us to construct the energy-reflection ratio. We infer the energy reflection's statistical variation with solar zenith angle, angle-of-incidence, frequency, and propagation azimuth. There is also a marginally-significant response of the energy reflectivity to solar X-ray flux density. Finally, we review the relationship of our results to previous published reports.

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