scholarly journals Vibration Excitation and Control of a Pedestrian Walkway by Individuals and Crowds

2005 ◽  
Vol 12 (5) ◽  
pp. 333-347 ◽  
Author(s):  
James Mark William Brownjohn ◽  
Tao Neng Fu
Keyword(s):  
Force Plate ◽  
Low Frequency ◽  
Modal Parameters ◽  
Modal Parameter ◽  
Low Frequency Vibration ◽  
Lateral Response ◽  
Single Mass ◽  
The Subject ◽  
Mass Spring ◽  
And Control

As part of a continuing study on effects of humans on loading and dynamic response of footbridges, a steel frame walkway has been the subject of studies on the effects of multiple pedestrians with respect to loading and response mitigation. Following finite element modeling and experimental modal analysis to identify the low frequency vibration modes likely to be excited by normal walking, the variation of response with pedestrian density and of system damping and natural frequency with occupancy by stationary pedestrians were both studied. The potentially mitigating effect of stationary occupants is still not well understood and the study included direct measurement of damping forces and absorbed energy using a force plate. The various tests showed that energy dissipation measured directly was consistent with the observed change in damping, that vertical and lateral response both varied approximately with square root of number of pedestrians, and that the simple model of a human as a single mass-spring-damper system may need to be refined to fit observed changes in modal parameters with a crowd of humans present. Modal parameter changes with moving pedestrians were small compared to those with stationary pedestrians indicating that within limits, modal parameters for the empty structure could be used in analysis.

Localized Vibration Isolation Strategy for Low-Frequency Excitations in Membrane Space Structures

2006 ◽  
Vol 128 (6) ◽  
pp. 790-797 ◽  
Author(s):  
Hiraku Sakamoto ◽  
K. C. Park
Keyword(s):  
Vibration Isolation ◽  
Controller Design ◽  
Low Frequency ◽  
Space Structures ◽  
Membrane Structures ◽  
Low Frequency Vibration ◽  
And Control ◽  
Structural Mass ◽  
The Web ◽  
Frequency Harmonic

The present study explores both structural and controller design to attenuate vibration in large membrane space structures, especially due to low-frequency harmonic excitations. It is very difficult for membrane structures to suppress the low-frequency vibration induced by flexible support structures, because a lightly prestressed membrane has extremely low mode frequencies and little damping effect. The present study proposes the use of weblike perimeter cables around a membrane, and the application of simple and lightweight active controllers only along the web cables in order to isolate the membrane from vibration. This strategy successfully reduces the membrane vibration when the web-cable configuration is appropriately tailored. Both linear and nonlinear finite-element analyses exhibit a clear tradeoff between structural mass and control efficiency.

Modeling a Viscoelastic Gymnastics Landing Mat during Impact

2006 ◽  
Vol 22 (2) ◽  
pp. 103-111 ◽  
Author(s):  
Chris Mills ◽  
Matthew T.G. Pain ◽  
Maurice R. Yeadon
Keyword(s):  
High Speed ◽  
Force Plate ◽  
System Model ◽  
Video Cameras ◽  
Key Characteristics ◽  
Single Mass ◽  
Force Time ◽  
Mass Spring ◽  
The Impact ◽  
Landing Mat

Landing mats that can undergo a large amount of area deformation are now essential for the safe completion of landings in gymnastics. The objective of this study was to develop an analytical model of a landing mat that reproduces the key characteristics of the mat-ground force during impact with minimal simulation run time. A force plate and two high-speed video cameras were used to record the mat deformation during vertical drop testing of a 24-kg impactor. Four increasingly complex point mass spring-damper models, from a single mass spring-damper system, Model 1, to a 3-layer mass spring-damper system, Model 4, were constructed using Matlab to model the mat's behavior during impact. A fifth model composed of a 3-layer mass spring-damper system was developed using visual Nastran 4D. The results showed that Models 4 and 5 were able to match the loading phase of the impact with simulation times of less than 1 second for Model 4 and 28 seconds for Model 5. Both Models 4 and 5 successfully reproduced the key force-time characteristics of the mat-ground interface, such as peak forces, time of peak forces, interpeak minima and initial rates of loading, and could be incorporated into a gymnast-mat model.

Theory and Application of Localized Vibration Control Strategy in Cable-Suspended Membrane Space Structures

Aerospace ◽  
2005 ◽  
Author(s):  
Hiraku Sakamoto ◽  
K. C. Park
Keyword(s):  
Controller Design ◽  
Low Frequency ◽  
Space Structures ◽  
Membrane Structures ◽  
Flexible Support ◽  
Low Frequency Vibration ◽  
And Control ◽  
Structural Mass ◽  
The Web ◽  
Frequency Harmonic

The present study explores both structural and controller design to attenuate vibration in large membrane structures especially due to low-frequency harmonic excitations. It is very difficult for membrane structures to suppress the low-frequency vibration induced by flexible support structures, because a lightly pre-stressed membrane has extremely low mode frequencies and little damping effect. The present study proposes the use of web-like perimeter cables around a membrane, and the application of simple and lightweight active controllers only along the web cables. This strategy successfully suppresses the membrane vibration when the web-cable configuration is appropriately tailored. Both linear and nonlinear finite-element analyses exhibit a clear tradeoff between structural mass and control efficiency.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

THE EFFECT OF APPLYING DEMONSTRATION METHOD ON STUDENTS’ ACHIEVEMENT IN SPEAKING SKILL AT THE THIRD GRADE OF SMK PAB 3 MEDAN ESTATE

2015 ◽  
Vol 4 (2) ◽  
Author(s):  
Meryanti Napitupulu And Anni Holila Pulungan
Keyword(s):  
High School ◽  
Control Group ◽  
Vocational High School ◽  
Control Groups ◽  
Speaking Test ◽  
The Third ◽  
Speaking Skill ◽  
The Subject ◽  
And Control ◽  
Experimental Group

This study was conducted as an attempt to discover the effect of applying Demonstration Method on students’ achievement in speaking skill. It was an experimental research. The subject was students of Grade XII, Vocational High School (Sekolah Menengah Kejuruan: SMK), which consisted of 79 students. The research was divided into two groups: experimental and control groups. The instrument used to collect the data was speaking test. To obtain the reliability of the test, the writer applied Kuder Richardson 21 formula. The result of the reliability was 0.7, and it was found that the test was reliable. The data were analyzed by using t-test formula. The analysis showed that the scores of the students in the experimental group were significantly higher than the scores of the students in the control group at the level of significant m = 0.05 with the degree of freedom (df) 77, t-observed value 8.9 > t-table value 1.99. The findings indicate that using Demonstration Method significantly affected the students’ achievement in speaking skill. So, English teachers are suggested to use Demonstration Method in order to improve students’ achievement in speaking skill.

The Implementation of Learning Materials Based on Local Wisdom of Agricultural in Binjai to Improve the Students Problem Solving Abilities

2019 ◽  
Author(s):  
Nur Tsalits Fahman Mughni
Keyword(s):  
Problem Solving ◽  
Control Group ◽  
School Grade ◽  
Teaching Materials ◽  
Quasi Experimental ◽  
Equivalent Control ◽  
The Subject ◽  
And Control ◽  
Experimental Group

Teaching materials by integrating local culture makes easier for students to understand the subject matter in the learning process. The aims of the study is to measure the effectiveness of teaching materials based on local wisdom of agriculture in Binjai in improving the students problem solving abilities. The research method was a quasi experimental which use non equivalent control group in the pretest posttest design. The sample of study were students of Senior High School grade X in Binjai that consisted of experiment group which used teaching materials based on local wisdom of agriculture in Binjai and control group that used student handbooks. Teaching materials are tested by material experts and technology experts to ensure the quality of teaching materials. Data collection was conducted through test. The results showed that the teaching materials based on local wisdom of agriculture in Binjai effective in improving students problem solving abilities in the experimental group students based on the results of N gain value was 0.67 which has medium criteria. It means teaching materials based on agricultural local wisdom of agriculture in Binjai can be used as one of the teaching materials in learning activities.

scholarly journals GMO Genetic Elements Thesaurus (GMO-GET): a controlled vocabulary for the consensus designation of introduced or modified genetic elements in genetically modified organisms

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Paulien Adamse ◽  
Emilie Dagand ◽  
Karen Bohmert-Tatarev ◽  
Daniela Wahler ◽  
Manoela Miranda ◽  
...  
Keyword(s):  
Genetically Modified Organisms ◽  
Genetically Modified ◽  
Controlled Vocabulary ◽  
Data Systems ◽  
Genetic Elements ◽  
Related Information ◽  
Detection And Identification ◽  
Unique Approach ◽  
The Subject ◽  
And Control

Abstract Background Various databases on genetically modified organisms (GMOs) exist, all with their specific focus to facilitate access to information needed for, e. g., the assistance in risk assessment, the development of detection and identification strategies or inspection and control activities. Each database has its unique approach towards the subject. Often these databases use different terminology to describe the GMOs. For adequate GMO addressing and identification and exchange of GMO-related information it is necessary to use commonly agreed upon concepts and terminology. Result A hierarchically structured controlled vocabulary describing the genetic elements inserted into conventional GMOs, and GMOs developed by the use of gen(om)e-editing is presented: the GMO genetic element thesaurus (GMO-GET). GMO-GET can be used for GMO-related documentation, including GMO-related databases. It has initially been developed on the basis of two GMO databases, i.e. the Biosafety Clearing-House and the EUginius database. Conclusion The use of GMO-GET will enable consistent and compatible information (harmonisation), also allowing an accurate exchange of information between the different data systems and thereby facilitating their interoperability. GMO-GET can also be used to describe genetic elements that are altered in organisms obtained through current targeted genome-editing techniques.

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