نتایج جستجو برای: acoustic
تعداد نتایج: 85922 فیلتر نتایج به سال:
In this paper with use of Particle in Cell (PIC) simulation method in one dimension the dynamic of ion acoustic soliton is studied. in this method the ions are monitored as particles and the electrons are assumed to be in thermal equilibrium. The dispersion relation of ion acoustic waves is investigated. The results are in good agreement with analytical results showing that in linear regime our...
In recent years, need to increase the convenience of trips in railway vehicles causes that train operators and manufacturers focus on reducing the noise level which is sensed by passengers. In this paper, first the state of modeling acoustic noise in cab train is discussed and natural frequencies and acoustic mode shapes are derived and then formulation of acoustic pressure in the cab will be o...
Investigating waves propagation’s equation in the atmosphere is one of the important and widely used issues in various sciences, which has attracted many researchers. A type of propagating waves is an acoustic-gravity wave. These type of waves have a lot of stationarity properties and can be propagate to a high altitude in the atmosphere. The equation of acoustic-gravity wave propagation is a h...
Introduction: The acoustic performance of natural fiber adsorbents has been investigated in numerous studies. A part of these materials show a poor adsorption within the frequency range of less than 1000 Hz. In the present study, attempts were made to investigate the effect of layout sequence of double-layered composites consisting of natural and synthetic fibers on improving the acoustic adsor...
Introduction: Microbubbles are widely used as contrast agent in diagnostic ultrasound. Recently they have shown good potential for applications in the therapeutic field such as drug delivery to the brain. Recent studies have shown focused ultrasound in conjunction with injected micro-bubbles could temporarily disrupt blood-brain barrier and let therapeutic agents transport into...
in recent years, need to increase the convenience of trips in railway vehicles causes that train operators and manufacturers focus on reducing the noise level which is sensed by passengers. in this paper, first the state of modeling acoustic noise in cab train is discussed and natural frequencies and acoustic mode shapes are derived and then formulation of acoustic pressure in the cab will be o...
background: the primary goal of antenatal testing is to identify fetuses at risk of intrauterine neurologic injury or death so that these adverse outcomes can be prevented. we want to assess nonstress test (nst) results and some parameters before and after vibro-acoustic stimulation and acupressure. we did a randomized controlled clinical trial in shahid-beheshti hospital in isfahan in 2011. ma...
Underwater acoustics is widely used in many applications, such as oceanography, marine biology, hydrography, fishery, etc. Different models are introduced to simulate the underwater acoustic propagation in the oceans and the seas. In this study, the Ray Theory model is used to simulate the acoustic wave propagation in a shallow-freshwater river (Gono River) located in western part of Japan. The...
in this study, the disadvantages of wood, which is widely employed in producing music instruments, are discussed. for example, high moisture sensitivity, low impact resistance, and time-consuming procedure as well as various properties of different species or in several parts of one specimen which are the main problems of wooden music instruments are extensively discussed in this paper. many ma...
Background: Since in multiple sclerosis (MS), changes in speech and voice quality often precede other signs and symptoms; early diagnosis of these changes is necessary. In this study, an acoustic examination of phonation subsystem was performed. Due to the progressive nature of multiple sclerosis, the aim of this study was to examine the correlation between acoustic parameters ...
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