نتایج جستجو برای: wave attenuation

تعداد نتایج: 263909  

2013
Z. KALÁB

Z. Kaláb, M. Stolárik, Institute of Geonics, Academy of Sciences, Czech Republic, B. Pandula, J. Kondela, Technical University of Košice, Institute of Geosciences, Slovakia The article summarizes experimental seismological measurements of vibration eff ects of blasting operations. During tunnel excavation can watch a variety of eff ects on the near or distant surroundings of the building. One o...

M Kaur, R Kumar, S.C Rajvanshi

The present study is concerned with the propagation of Lamb waves in a homogeneous isotropic thermoelastic micropolar solid with two temperatures bordered with layers or half spaces of inviscid liquid subjected to stress free boundary conditions. The generalized theory of thermoelasticity developed by Lord and Shulman has been used to investigate the problem. The secular equations for symmetric...

2007
EINAR KJARTANSSON

A linear model for attenuation of waves is presented, with Q, or the portion of energy lost during each cycle or wavelength, exactly independent of frequency. The wave propagation is completely specified by two parameters, e.g., Q and Co, a phase velocity at an arbitrary reference frequency w0. A simple exact derivation leads to an expression for the phase velocity c as a function of frequency:...

2012
Milda Tamošiūnaitė Mindaugas Žilinskas Milda Tamošiūnienė Stasys Tamošiūnas

Humidity remains in the atmosphere even on bright days. Water of all three states can be found naturally in the atmosphere: liquid (rain, fog, and clouds), solid (snowflakes, ice crystals), and gas (water vapour). Water in any state is an obstacle in the link of the electromagnetic wave. When the wave passes through the water particles, a part of its energy is absorbed and a part is scattered. ...

Journal: :فیزیک زمین و فضا 0
فائزه شیرمحمدی دانشجوی کارشناسی ارشد، گروه فیزیک زمین، موسسه ژئوفیزیک، دانشگاه تهران، ایران ظاهر حسین شمالی دانشیار، گروه فیزیک زمین، موسسه ژئوفیزیک، دانشگاه تهران، ایران مهرداد پاکزاد استادیار، گروه فیزیک زمین، موسسه ژئوفیزیک، دانشگاه تهران، ایران

in many seismological applications, the earth is considered as a perfectly elastic, homogeneous, and isotropic body. although this assumption is approximately valid, it is known that seismic waves pass through the real earth that is anelastic, inhomogeneous and anisotropic.  we consider four processes that can reduce wave amplitude, i.e.: geometrical spreading, scattering, multi-pathing, and an...

Journal: :IEICE Transactions 2005
Shoichi Kajiwara Atsushi Yamamoto Koichi Ogawa Akihiro Ozaki Yoshio Koyanagi

where E [V/m] is the amplitude of effective value of the electric field, σ [S/m] and ρ [kg/m] are the electric conductivity and the density of human tissue, respectively. In general, an approximation of a plane wave for the electromagnetic field has been applied to E in eq. (1) in order to represent the SAR characteristics in the internal parts of the head [1], [4]. For example, attenuation cha...

2012
E. Infantes

We demonstrate the utility of using the equivalent bottom roughness for calculating the friction factor and the drag coefficient of a seagrass meadow for conditions in which the meadow height is small compared to the water depth. Wave attenuation induced by the seagrass Posidonia oceanica is evaluated using field data from bottom-mounted acoustic doppler veloci meters (ADVs). Using the data fro...

2012
M. Tang

This study investigates the propagation of borehole Stoneley waves across heterogeneous and permeable structures. By modeling the structure as a zone intersecting the borehole, a simple one-dimensional theory is formulated to treat the interaction of the Stoneley wave with the structure. This is possible because the Stoneley wave is a guided wave, with no geometric spreading as it propagates al...

2014
Yuanming Ding Jingjing Sun Xue Wang

Ultra High Frequency (UHF) band is increasingly widely used in military maritime satellite communications due to its good communication performance. Electromagnetic wave emitted by satellite is reflected when reaching the sea surface, and multipath fading is very serious which causes interference on the received signal, especially when satellite elevation angle is low. In this paper, the UHF ba...

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