Line Source Of Finite Length Research Articles

Acoustic field radiated by an impulsively excited line source of finite length

A new closed-form theoretical expression is derived that describes the transient acoustic pressure field that is radiated when a line source of finite length impulsively excites the fluid surrounding it. The new expression, which is obtained by solving the two-dimensional scalar wave equation by integral-transform techniques,describes the acoustic field of the finite line, in the time-domain, in terms of generalized functions. The results obtained, which support the ideas advanced in the Rubinowicz-Maggi diffraction theory, show that the field of a line source is comprised of three distinct components: a spatially discontinuous cylindrical wave (“geometrical wave”) and two directional boundary-diffraction waves radiated by the ends of the line. There is a direct analogy between the results reported in this paper and those given by Schoch in his classic paper on the radiated acoustic fields of planar sources.

Two-Dimensionality and end Correction in Gravity Prospecting with an Inverse Solution of a Line Source of Finite Length

An ideal two-dimensional mass distribution is in fact a three-dimensional distribution which has an infinitely long dimension and does not change its configuration or density along this dimension. The condition that the long dimension be horizontal and the sphericity of the earth do not exclude the assumption of two dimensionality provided an end correction is applied in appropriate cases.

Dispersi Polutan Karbon Monoksida di Sekitar Pintu Tol Baranangsiang Bogor (Carbon monoxide Dispersion in the Vicinity of Baranangsiang Toll Gateway in Bogor)

Over the past decade, emission from carbon monoxide (CO) has risen due to the increase of vehicles per year. Bogor as a weekend tourist tour town has a heavy burden in the terms of the volume of motor vehicles. The object of this study is Baranangsiang Bogor toll gateway, where queue of motor vehicles is often the case, and allegedly produces many pollutants CO. This study was conductes to simulate the CO concentration by the method of Finite Length Line Source (FLLS) aroung Baranangsiang Bogor toll gateway and recapitulate types of diseases associated with CO impacts on communities around the toll is in line with the pattern of increase in the volume of vehicles at 6% per years. Based on the result of measurements and simulations that were conducted on four sampling points within 20 m and 190 m from the sources pollutions on 26th August to 1st September 2014, the concentration of CO is still within the range of quality standards in accordance with Regulation No. 41 of 1999 which is 634-9189 µg/Nm3. Dispesion of pollutants CO dominantly heading Eastwards with the wind speed measurements 1.5-5.2 m/s and atmospheric stability class B. Kampung Sawah RT 02 RW 07is exposed to higher CO. Recapitulation of medical records showed that CO intoxication suspected cases of the disease are more common in Kampung Sawah housing than IPB Baranangsiang 4 Settlement.Keywords : Baranangsiang Toll Gate, Carbon Monoxide, CO Intoxication, Dispersion CO

Disturbances produced by variable body forces in a layer of finite thickness resting on a rigid foundation

The disturbances produced by time-dependent torsional body forces in a layer of elastic material lying on a rigid foundation have been discussed in this paper. Solutions have been obtained first for a general type of body force, and the solutions for an impulsive cylindrical source and an impulsive torsional line source of finite length have been deduced. It has been found that for any point in the layer, there is no disturbance up to a certain instant, after which there is a sudden displacement, which gradually falls off and tends to zero as the timet increases.

Acoustic Radiation from a Finite Cylinder

A semianalytic method is presented that can be used to calculate the acoustic radiation in a domain exterior to a source that is vibrating harmonically in time. This method follows the traditional technique of an expansion of the boundary conditions in an infinite series of eigenfunctions and of a least-squares approximation of this expansion by a finite series of the same functions. For simply connected bodies, such as a finite cylinder, that are not constant coordinate surfaces and for which a complete set of geometrically appropriate eigenfunctions is unavailable, the spherical eigenfunctions are employed as the complete set of eigenfunctions. Farfield patterns produced by radially pulsating cylinders of length equal to twice the diameter have been calculated for ka = 1,2, and 5 and are compared to the calculated farfield patterns of the physically similar situations of a finite-length line source and a radially pulsating band of finite length on an otherwise inert, infinite cylinder. In addition, the radiation resistance and directivity index are calculated and compared for the finite and infinite cylinder sources.

Synthesis of Line Source Directivity Patterns

The distribution of sound intensity in space (pattern function) from a line source of finite length is given by an integral involving the distribution of source strength along the line of the source (excitation function). Synthesizing a desired pattern function with a given length of source requires the solution of an integral equation for the excitation function. Practical solutions may be obtained by expressing the pattern function as a finite sum of “characteristic functions” and obtaining the excitation function as a similar sum of complementary functions. One such scheme relates the zeroes of the pattern function to the coefficients of the Fourier expansion of the excitation function. Equal-minor-lobe patterns may be approximated, but the solution is not obtained in closed form as with linear point-source arrays.