scholarly journals Research on dynamic characteristics test of wooden floor structure for gymnasium

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Adam Guo
Keyword(s):  
Double Layer ◽  
Load Distribution ◽  
Optimization Design ◽  
Absorption Rate ◽  
Damping Ratio ◽  
Engineering Application ◽  
Single Layer ◽  
Structural Vibration ◽  
Wooden Floor ◽  
Floor Structure

In order to better evaluate the structural performance of the wooden floor used in the gymnasium and realize the structural optimization design, this research considered two gymnasium’s floors in Nanjing as the research object and used the transient excitation method to test the natural frequency and damping ratio parameters of the three types of floor structures. The results showed that three kinds of floor structures all meet the requirements of building comfort; under the premise that the types and specifications of the constituent materials were the same, the order of the damping ratios of the three kinds of floor structures from large to small was: the fixed floor structure with double-layer load distribution strip, the suspended floor structure with single-layer load distribution strip, and the suspended floor structure with double-layer load distribution strip; compared with the fixed floor structure, the suspended floor structure had low damping ratio characteristics, the energy dissipation was slow during structural vibration, which means its impact absorption rate was small, and its impact buffering ability was good. The integral structure had good resilience performance; compared with the floor structure using single-layer load distribution strip. The floor structure using a double-layer load distribution strip had a low damping ratio characteristic. The absorption rate of the structure was small and the resilience performance was good. The research conclusion had certain engineering application value.

scholarly journals Exact Solutions for a Novel H2 Optimal Design of Electromagnetic Tuned Mass Damper

2021 ◽  
Author(s):  
Ge Li ◽  
Qibo Mao ◽  
Yifan Luo ◽  
Yong Wang ◽  
Lei Liu
Keyword(s):  
Vibration Control ◽  
Optimization Design ◽  
Damping Ratio ◽  
Tuned Mass Damper ◽  
Parameters Optimization ◽  
Structural Vibration ◽  
Control Effect ◽  
Mass Damper ◽  
Two Parameters ◽  
H2 Optimization

To realize structural vibration control,a two parameters H2 optimization design was proposed to optimize the tuning ratio and damping ratio for electromagnetic tuned mass damper (EMTMD). The control effect of this two parameters optimization design is better than that of classical tuned mass damper (TMD).For this two parameters optimization,the most important thing is that the inductance of the coil can be set very small and the external load resistance can be positive ,which can avoid the use of complex negative impedance circuit. If Ref.[6] were designed according to the H2 optimization of two parameters, the EMTMD can be used for multi-modal vibration control of structures without connecting negative inductance and negative resistance spontaneously.

Cracking at the fold in double layer coated paper: the influence of latex and starch composition

TAPPI Journal ◽  
2019 ◽  
Vol 18 (2) ◽  
pp. 93-99
Author(s):  
SEYYED MOHAMMAD HASHEMI NAJAFI ◽  
DOUGLAS BOUSFIELD, ◽  
MEHDI TAJVIDI
Keyword(s):  
Mechanical Properties ◽  
Double Layer ◽  
Starch Content ◽  
Single Layer ◽  
Double Layers ◽  
Coated Paper ◽  
Coated Papers ◽  
Coating Layers ◽  
Scanned Images ◽  
Packaging Paper

Cracking at the fold of publication and packaging paper grades is a serious problem that can lead to rejection of product. Recent work has revealed some basic mechanisms and the influence of various parameters on the extent of crack area, but no studies are reported using coating layers with known mechanical properties, especially for double-coated systems. In this study, coating layers with different and known mechanical properties were used to characterize crack formation during folding. The coating formulations were applied on two different basis weight papers, and the coated papers were folded. The binder systems in these formulations were different combinations of a styrene-butadiene latex and mixtures of latex and starch for two different pigment volume concentrations (PVC). Both types of papers were coated with single and double layers. The folded area was scanned with a high-resolution scanner while the samples were kept at their folded angle. The scanned images were analyzed within a constant area. The crack areas were reported for different types of papers, binder system and PVC values. As PVC, starch content, and paper basis weight increased, the crack area increased. Double layer coated papers with high PVC and high starch content at the top layer had more cracks in comparison with a single layer coated paper, but when the PVC of the top layer was low, cracking area decreased. No measurable cracking was observed when the top layer was formulated with a 100% latex layer.

Single layer versus double layer suture for anastomosis of the gastrointestinal tract

2009 ◽  
Author(s):  
Alvaro Sanabria ◽  
Gabriel Gomez ◽  
Eduardo Valdivieso ◽  
C Bermudez
Keyword(s):  
Gastrointestinal Tract ◽  
Double Layer ◽  
Single Layer ◽  
Layer Versus

Single layer versus double layer suture for anastomosis of the gastrointestinal tract

2005 ◽  
Author(s):  
Alvaro Sanabria ◽  
Gabriel Gomez ◽  
Eduardo Valdivieso ◽  
C Bermudez
Keyword(s):  
Gastrointestinal Tract ◽  
Double Layer ◽  
Single Layer ◽  
Layer Versus

scholarly journals Electron-phonon interaction in In-induced √7 ×√3 structures on Si(111) from first-principles

2021 ◽  
Author(s):  
I. Yu. Sklyadneva ◽  
Rolf Heid ◽  
Pedro Miguel Echenique ◽  
Evgueni Chulkov
Keyword(s):  
Density Functional Theory ◽  
Double Layer ◽  
First Principles ◽  
Linear Response ◽  
Density Functional ◽  
Single Layer ◽  
Phonon Interaction ◽  
Functional Theory ◽  
Electron Phonon Interaction ◽  
The Density Functional Theory

Electron-phonon interaction in the Si(111)-supported rectangular √(7 ) ×√3 phases of In is investigated within the density-functional theory and linear-response. For both single-layer and double-layer √(7 ) ×√3 structures, it...

scholarly journals A Trial Acoustic Improvement in a Lecture Hall with MPP Sound Absorbers and FDTD Acoustic Simulations

2021 ◽  
Vol 11 (6) ◽  
pp. 2445
Author(s):  
Matteo Cingolani ◽  
Giulia Fratoni ◽  
Luca Barbaresi ◽  
Dario D’Orazio ◽  
Brian Hamilton ◽  
...  
Keyword(s):  
Double Layer ◽  
Speech Intelligibility ◽  
Single Layer ◽  
Lecture Hall ◽  
Full Spectrum ◽  
Metal Printing ◽  
Specific Impedance ◽  
Specific Material ◽  
Acoustic Treatment ◽  
Difference Time

Sound absorbing micro-perforated panels (MPPs) are being increasingly used because of their high quality in terms of hygiene, sustainability and durability. The present work investigates the feasibility and the performance of MPPs when used as an acoustic treatment in lecture rooms. With this purpose, three different micro-perforated steel specimens were first designed following existing predictive models and then physically manufactured through 3D additive metal printing. The specimens’ acoustic behavior was analyzed with experimental measurements in single-layer and double-layer configurations. Then, the investigation was focused on the application of double-layer MPPs to the ceiling of an existing university lecture hall to enhance speech intelligibility. Numerical simulations were carried out using a full-spectrum wave-based method: a finite-difference time-domain (FDTD) code was chosen to better handle time-dependent signals as the verbal communication. The present work proposes a workflow to explore the suitability of a specific material to speech requirements. The measured specific impedance complex values allowed to derive the input data referred to MPPs in FDTD simulations. The outcomes of the process show the influence of the acoustic treatment in terms of reverberation time (T30) and sound clarity (C50). A systematic comparison with a standard geometrical acoustic (GA) technique is reported as well.

scholarly journals Ileo-colic intra-corporeal anastomosis during robotic right colectomy: a systematic literature review and meta-analysis of different techniques

2021 ◽  
Author(s):  
Simone Guadagni ◽  
Matteo Palmeri ◽  
Matteo Bianchini ◽  
Desirée Gianardi ◽  
Niccolò Furbetta ◽  
...  
Keyword(s):  
Double Layer ◽  
Meta Analysis ◽  
Single Layer ◽  
Right Colectomy ◽  
Layer Versus ◽  
Bleeding Rate ◽  
Common Technique ◽  
Technical Details ◽  
Robotic Right Colectomy ◽  
Mechanical Anastomosis

Abstract Purpose Robotic assistance could increase the rate of ileo-colic intra-corporeal anastomosis (ICA) during robotic right colectomy (RRC). However, although robotic ICA can be accomplished with several different technical variants, it is not clear whether some of these technical details should be preferred. An evaluation of the possible advantage of one respect to another would be useful. Methods We conducted a systematic review of literature on technical details of robotic ileo-colic ICA, from which we performed a meta-analysis of clinical outcomes. The extracted data allowed a comparative analysis regarding the outcome of overall complication (OC), bleeding rate (BR) and leakage rate (LR), between (1) mechanical anastomosis with robotic stapler, versus laparoscopic stapler, versus totally hand-sewn anastomosis and (2) closure of enterocolotomy with manual double layer, versus single layer, versus stapled. Results A total of 30 studies including 2066 patients were selected. Globally, the side-to-side, isoperistaltic anastomosis, realized with laparoscopic staplers, and double-layer closure for enterocolotomy, is the most common technique used. According to the meta-analysis, the use of robotic stapler was significantly associated with a reduction of the BR with respect to mechanical anastomosis with laparoscopic stapler or totally hand-sewn anastomosis. None of the other technical aspects significantly influenced the outcomes. Conclusions ICA fashioning during RRC can be accomplished with several technical variants without evidence of a clear superiority of anyone of these techniques. Although the use of robotic staplers could be associated with some benefits, further studies are necessary to draw conclusions.

scholarly journals Identification of Dynamic Parameters of Pedestrian Walking Model Based on a Coupled Pedestrian–Structure System

2021 ◽  
Vol 11 (14) ◽  
pp. 6407
Author(s):  
Huiqi Liang ◽  
Wenbo Xie ◽  
Peizi Wei ◽  
Dehao Ai ◽  
Zhiqiang Zhang
Keyword(s):  
Negative Correlation ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Testing ◽  
The Body ◽  
Structural Vibration ◽  
Pedestrian Dynamics ◽  
Structure Interaction ◽  
Mass Spring ◽  
Stiffness And Damping

As human occupancy has an enormous effect on the dynamics of light, flexible, large-span, low-damping structures, which are sensitive to human-induced vibrations, it is essential to investigate the effects of pedestrian–structure interaction. The single-degree-of-freedom (SDOF) mass–spring–damping (MSD) model, the simplest dynamical model that considers how pedestrian mass, stiffness and damping impact the dynamic properties of structures, is widely used in civil engineering. With field testing methods and the SDOF MSD model, this study obtained pedestrian dynamics parameters from measured data of the properties of both empty structures and structures with pedestrian occupancy. The parameters identification procedure involved individuals at four walking frequencies. Body frequency is positively correlated to the walking frequency, while a negative correlation is observed between the body damping ratio and the walking frequency. The test results further show a negative correlation between the pedestrian’s frequency and his/her weight, but no significant correlation exists between one’s damping ratio and weight. The findings provide a reference for structural vibration serviceability assessments that would consider pedestrian–structure interaction effects.

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