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Earliest Stone-Tipped Projectiles from the Ethiopian Rift Date to >279,000 Years Ago

Sahle, Yonatan; Hutchings, W. Karl; Braun, David R.; Sealy, Judith C.; Morgan, Leah E.; Negash, Agazi; Atnafu, Balemwal
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 13/11/2013 EN
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Projectile weapons (i.e. those delivered from a distance) enhanced prehistoric hunting efficiency by enabling higher impact delivery and hunting of a broader range of animals while reducing confrontations with dangerous prey species. Projectiles therefore provided a significant advantage over thrusting spears. Composite projectile technologies are considered indicative of complex behavior and pivotal to the successful spread of Homo sapiens. Direct evidence for such projectiles is thus far unknown from >80,000 years ago. Data from velocity-dependent microfracture features, diagnostic damage patterns, and artifact shape reported here indicate that pointed stone artifacts from Ethiopia were used as projectile weapons (in the form of hafted javelin tips) as early as >279,000 years ago. In combination with the existing archaeological, fossil and genetic evidence, these data isolate eastern Africa as a source of modern cultures and biology.

Inviscid aerodynamic predictions of hypersonic elliptical projectiles: a comparative study of the effects of stabilizing surfaces

Boyle, Christopher
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xviii, 120 p.;ills.
EN_US
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Approved for public release, distribution is unlimited; With the advent of "smart" munitions, the US and its allies are attempting to design more accurate tactical weapons. Of interest are relatively inexpensive barrel-launched projectiles capable of accuracy associated with guided munitions. This research studies potential configurations for a new class of kinetic energy projectiles. From past research, it has been shown that projectiles with elliptical cross-sections are more stable in flight than those with circular cross-sections. This research looks at one particular shape, an elliptical cone, and numerically predicts the aerodynamic attributes in inviscid, steady, hypersonic flow. In particular, the effects of different stabilizing surface configurations are evaluated. A residual benefit of this research is to show that ZEUS, an afterbody solver typically used for missile design, is capable of providing solutions for these configurations. The findings of this research will be delivered to the Chief, Aerodynamics Branch, Army Research Laboratory, and will fulfill part of ARL's commitment in a Key Technical Area agreement with the research laboratories of our allies.; http://www.archive.org/details/inviscidaerodyna00boyl; Captain...

Penetration of Granular Projectiles into a Water Target

González-Gutiérrez, Jorge; Carrillo-Estrada, J. L.; Ruiz-Suárez, J. C.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 24/10/2014 EN
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The penetration of low-speed projectiles into a water target has been studied in the last several years to understand the physics behind the formation and collapse of cavities. In such studies, the projectiles employed were solid bodies or liquid drops. Here we report similar impact experiments using granular projectiles, with the aim to investigate how the morphology of the cavities is determined by the balance between the dynamic pressure exerted by the fluid and the cohesive strength of the impactors. From the results we present and discuss in this manuscript, we speculate on the dynamics of meteorite disintegration in the atmosphere of our planet.

Reacciones nucleares de fragmentación con proyectiles débilmente ligados; Nuclear breakup reactions with weakly bound projectiles

Martínez Heimann, Diego
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2013 SPA
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A partir de la disponibilidad de instalaciones capaces de producir haces radiactivos, gran parte de las actividades dentro del marco de la física nuclear experimental y teórica han sido orientadas al estudio de reacciones con núcleos en zonas alejadas del denominado valle de estabilidad. Al mismo tiempo, la existencia de ciertos núcleos estables pero débilmente ligados, con muchas características similares (como ser por ejemplo el bajo umbral de energía de separación), brinda la posibilidad de estudiar este tipo de mecanismos con la ventaja adicional de poder ser producidos en forma más sencilla y con flujos de mayor intensidad. Entre los distintos mecanismos que pueden tener lugar en las interacciones con núcleos inestables o débilmente ligados, el proceso de quiebre o breakup resulta de particular interés por diversos motivos. Dentro del área de astrofísica nuclear, se ha propuesto que el estudio del mecanismo de breakup de núcleos livianos permitiría la determinación de secciones eficaces de captura radiativa a través del proceso inverso. Por otro lado, en el contexto de la física de reacciones en general, el interés está puesto en entender, no solo los mecanismos que dan lugar a este tipo de procesos por la comprensión del fenómeno en sí mismo...

Decay analysis of compound nuclei with mass A$\sim 30-200$ formed in the reactions involving loosely bound projectiles

Kaur, Mandeep; Singh, BirBikram; Sharma, Manoj K.; Gupta, Raj K.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/06/2015
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The dynamics of the reactions forming compound nuclei using loosely bound projectiles is analysed within the framework of dynamical cluster decay model (DCM) of Gupta and Collaborators. We have analysed different reactions with $^{7}Li$, $^{9}Be$ and $^{7}Be$ as neutron rich and neutron deficient projectiles, respectively, on different targets at the three $E_{lab}$ values, forming compound nuclei within the mass region A$\sim 30-200$. The contributions of light particles LPs ($A\le4$) cross sections $\sigma_{LP}$, energetically favoured intermediate mass fragments IMFs ($5 \le A_2 \le 20$) cross sections $\sigma_{IMF}$ as well as fusion-fission $\it{ff}$ cross sections $\sigma_{ff}$ constitute the $\sigma_{fus}$ (=$\sigma_{LP}$+$\sigma_{IMF}$+$\sigma_{ff}$) for these reactions. The contribution of the emitted LPs, IMFs and ff fragments is added for all the angular momentum upto the $\ell_{max}$ value, for the resepctive reactions. Interestingly, we find that the $\Delta R^{emp}$, the only parameter of model and uniquely fixed to address the $\sigma_{fus}$ for all other reactions having $\it same$ loosely bound projectile at the chosen incident energy. It may be noted that the dynamical collective mass motion of preformed LPs, IMFs and ff fragments or clusters through the modified interaction potential barrier are treated on parallel footing. We see that the values of modified interaction barrier heights $\Delta V_{B}^{emp}$ for such reactions are almost of the same amount specifically at the respective $\ell_{max}$ values.

Experimental Tests of the Proportionality of Aerodynamic Drag to Air Density for Supersonic Projectiles

Courtney, Elya; Courtney, Amy; Courtney, Michael
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/10/2015
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Pure theory recognizes the dependence of supersonic drag coefficients on both Mach number and Reynolds number, which includes an implicit dependence of drag coefficient on air density. However, many modern approaches to computing trajectories for artillery and small arms treat drag coefficients as a function of Mach number and assume no dependence on Reynolds number. If drag force is strictly proportional to air density for supersonic projectiles (as suggested by applied theory), the drag coefficient should be independent of air density over a range of Mach numbers. Experimental data to directly support this are not widely available for supersonic projectiles. The experiment determined drag on a 2.59 g projectile from M1.2 to M2.9 using optical chronographs to measure initial and final velocities over a separation of 91.44 m. The free flight determination of drag coefficients was performed at two significantly different atmospheric densities (0.93 kg/m3 and 1.15 kg/m3 ). This experiment supported direct proportionality of aerodynamic drag to air density from M1.2 to M2.9 within the experimental error of 1%-2%.

Breakup reaction models for two- and three-cluster projectiles

Baye, D.; Capel, P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/11/2010
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Breakup reactions are one of the main tools for the study of exotic nuclei, and in particular of their continuum. In order to get valuable information from measurements, a precise reaction model coupled to a fair description of the projectile is needed. We assume that the projectile initially possesses a cluster structure, which is revealed by the dissociation process. This structure is described by a few-body Hamiltonian involving effective forces between the clusters. Within this assumption, we review various reaction models. In semiclassical models, the projectile-target relative motion is described by a classical trajectory and the reaction properties are deduced by solving a time-dependent Schroedinger equation. We then describe the principle and variants of the eikonal approximation: the dynamical eikonal approximation, the standard eikonal approximation, and a corrected version avoiding Coulomb divergence. Finally, we present the continuum-discretized coupled-channel method (CDCC), in which the Schroedinger equation is solved with the projectile continuum approximated by square-integrable states. These models are first illustrated by applications to two-cluster projectiles for studies of nuclei far from stability and of reactions useful in astrophysics. Recent extensions to three-cluster projectiles...

Search of systematic behavior of breakup probability in reactions with weakly bound projectiles at energies around Coulomb barrier

Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.; Zhang, H. Q.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Comparing the capture cross sections calculated without the breakup effect and experimental complete fusion cross sections, the breakup was analyzed in reactions with weakly bound projectiles $^{6,7,9}$Li, $^{9,11}$Be, and $^{6,8}$He. A trend of a systematic behavior for the complete fusion suppression as a function of the target charge and bombarding energy is not achieved. The quasielastic backscattering is suggested to be an useful tool to study the behavior of the breakup probability in reactions with weakly bound projectiles.; Comment: 15 pages, 15 figures, accepted in PRC

Energy losses of fast heavy-ion projectiles in dense hydrogen plasmas

Ballester, D.; Tkachenko, I. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/12/2008
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It has been recently shown that the Bethe-Larkin formula for the energy losses of fast heavy-ion projectiles in dense hydrogen plasmas is corrected by the electron-ion correlations [Phys. Rev. Lett. \textbf{101}, 075002 (2008)]. We report numerical estimates of this correction based on the values of $g_{ei}(0)$ obtained by numerical simulations in [Phys. Rev. E \textbf{61}, 3470 (2000)]. We also extend this result to the case of projectiles with dicluster charge distribution. We show that the experimental visibility of the electron-ion correlation correction is enhanced in the case of dicluster projectiles with randomly orientated charge centers. Although we consider here the hydrogen plasmas to make the effect physically more clear, the generalization to multispecies plasmas is straightforward.; Comment: 5 pages, 1 figure. International Conference on Strongly Coupled Coulomb Systems 2008, Camerino (Italy). To appear in J. Phys. A

Status of art of reaction models for projectiles far from stability

Bonaccorso, Angela
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/06/2007
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This talk will review the status of art of nuclear and Coulomb breakup theories and their relation to optical models of elastic scattering of exotic projectiles. The effect of the final state interactions between the breakup particle and the core and target nuclei will be clarified and some typical numerical calculations for the relevant observables will be presented and compared to experimental data. Finally new results will be shown to demonstrate the feasibility of a novel type of experiment involving heavy projectiles far from stability on heavy targets.; Comment: 10 pages, 4 figures. Proceedings of NN2007, Rio de Janeiro

Prospects for the discovery of the next new element: Influence of projectiles with Z > 20

Folden III, Charles M; Mayorov, Dmitriy A; Werke, Tyler A; Alfonso, Marisa C; Bennett, Megan E; DeVanzo, Michael J
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/09/2012
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The possibility of forming new superheavy elements with projectiles having Z > 20 is discussed. Current research has focused on the fusion of 48Ca with actinides targets, but these reactions cannot be used for new element discoveries in the future due to a lack of available target material. The influence on reaction cross sections of projectiles with Z > 20 have been studied in so-called analog reactions, which utilize lanthanide targets carefully chosen to create compound nuclei with energetics similar to those found in superheavy element production. The reactions 48Ca, 45Sc, 50Ti, 54Cr + 159Tb, 162Dy have been studied at the Cyclotron Institute at Texas A&M University using the Momentum Achromat Recoil Spectrometer. The results of these experimental studies are discussed in terms of the influence of collective enhancements to level density for compound nuclei near closed shells, and the implications for the production of superheavy elements. We have observed no evidence to contradict theoretical predictions that the maximum cross section for the 249Cf(50Ti, 4n)295120 and 248Cm(54Cr, 4n)298120 reactions should be in the range of 10-100 fb.; Comment: An invited talk given by Charles M. Folden III at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012)...

AB-Net Method of Protection from Projectiles (city, military base, battle-front, etc.)

Bolonkin, Alexander
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/02/2008
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The author suggests a low cost special AB-Net from artificial fiber, which may protect cities and important objects from rockets, artillery and mortar shells, projectiles, bullets, and strategic weapons. The idea is as follows: The offered AB-Net joins an incoming projectile to a small braking parachute and this incoming projectile loses speed by air braking after a drag distance of 50 - 150 meters. A following interception net after the first may serve to collect the slowed projectiles and their fragments or bomblets so that they do not reach the aimpoint. The author offers the design of AB-Net, a developed theory of snagging with a small braking parachute by AB-Net; and sample computations. These nets may be used for defense of a town, city, military base, battle-front line, road (from terrorists), or any important objects or installations (for example nuclear electric station, government buildings, etc.). Computed projects are: Net to counter small rockets (for example, from Qassam), net to counter artillery projectile (caliber 76 mm), net to counter bullets (caliber 7.6 mm). The offered method is cheaper by thousands of times than protection of a city by current anti-rocket systems. Discussion and results are at the end of the article. Key words: Protection from missile and projectile weapons...

Production of neutron-rich nuclei in fragmentation reactions of 132Sn projectiles at relativistic energies

Pérez-Loureiro, D.; Benlliure, J.; Álvarez-Pol, H.; Blank, B.; Casarejos, E.; Dragosavac, D.; Föhr, V.; Gascón, M.; Gawlikowicz, W.; Heinz, A.; Helariutta, K.; Kelić, A.; Lukić, S.; Montes, F.; Pieńkowski, L.; Schmidt, K-H.; Staniou, M.; Subotić,
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/05/2011
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The fragmentation of neutron-rich 132Sn nuclei produced in the fission of 238U projectiles at 950 MeV/u has been investigated at the FRagment Separator (FRS) at GSI. This work represents the first investigation of fragmentation of medium-mass radioactive projectiles with a large neutron excess. The measured production cross sections of the residual nuclei are relevant for the possible use of a two-stage reaction scheme (fission+fragmentation) for the production of extremely neutron-rich medium-mass nuclei in future rare-ion-beam facilities. Moreover, the new data will provide a better understanding of the "memory" effect in fragmentation reactions.; Comment: 5 pages, 3 figures

Electron loss of fast heavy projectiles in collision with neutral targets

Matveev, V. I.; Ryabchenko, S. V.; Matrasulov, D. U.; Rakhimov, Kh. Yu.; Fritzsche, S.; Stöhlker, Th.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/06/2011
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The multiple electron loss of heavy projectiles in fast ion-atom collisions has been studied in the framework of the sudden perturbation approximation. Especially, a model is developed to calculate the cross sections for the loss of any number of electrons from the projectile ion, including the ionization of a single electron and up to the complete stripping of the projectile. For a given collision system, that is specified by the (type and charge state of the) projectile and target as well as the collision energy, in fact, the experimental cross sections for just three final states of the projectile are required by this model in order to predict the loss of any number, $N$, of electrons for the same collision system, or for any similar system that differs only in the energy or the initial charge state of the projectile ion. The model is simple and can be utilized for both, the projectile and target ionization, and without that large computer resources are requested. Detailed computation have been carried out for the multiple electron loss of Xe$^{18+}$ and U$^{6+,\, 10+,\, 28+}$ projectiles in collision with neutral Ar and Ne gas targets.

Effect of the break-up on the fusion and elastic scattering of weakly bound projectiles on $^{64}$Zn

Gomes, P. R. S.; Rodriguez, M. D.; Marti, C. V.; Padron, I.; Chamon, L. C.; Niello, J. O. Fernandez; Capurro, O. A.; Pacheco, A. J.; Testoni, J. E.; Arazi, A.; Ramirez, M.; Anjos, R. M.; Lubian, J.; Viega, R.; Neto, R. Liguori; Crema, E.; Added, N.; Tenre
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/02/2005
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We study the behavior of the fusion, break-up, reaction and elastic scattering of different projectiles on $^{64}$Zn, at near and above barrier energies. We present fusion and elastic scattering data with the tightly bound $^{16}$O and the stable weakly bound $^{6}$Li, $^{7}$Li and $^{9}$Be projectiles. The data were analyzed by coupled channel calculations. The total fusion cross sections for these systems are not affected by the break-up process at energies above the barrier. The elastic (non-capture) break-up cross section is important at energies close and above the Coulomb barrier and increases the reaction cross sections. In addition we also show that the break-up process at near and sub-barrier energies is responsible for the vanishing of the usual threshold anomaly of the optical potential and give rise to a new type of anomaly.; Comment: 24 pages, 10 figures

Microscopic effects in fragment mass distribution in fusion-fission reactions of light projectiles with heavy targets

Ghosh, T. K.; Pal, S.; Golda, K. S.; Bhattacharya, P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/02/2005
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Microscopic effects in fragment mass distributions in fusion-fission reactions of light projectiles (C, O and F) on deformed thorium and spherical bismuth targets in near and below Coulomb barrier energies are investigated. Precisely measured mass distribution shows a sudden anomalous increase in variances of mass distributions ($\sigma_{m}^2$) near Coulomb barrier energies for all three projectiles with deformed thorium target, in contrast to a smooth variation of $\sigma_{m}^2$ with energy for spherical bismuth target. Macroscopic effects of change in mass flow or prolonged mass equilibration time can not explain the observed variation in $\sigma_{m}^2$ with energy. Microscopic effects due to change in entrance channel shape compactness for projectiles hitting the polar region of prolate thorium target is postulated to reach a almost symmetric saddle without complete fusion for events of anomalous fragment widths. Quantitative estimates of mass widths mixed for the two processes explains the observed variation of $\sigma_{m}^2$ with excitation energy.; Comment: 11 pages, 4 figures

On High Explosive Launching of Projectiles for Shock Physics Experiments

Swift, Damian C.; Forest, Charles A.; Clark, David A.; Buttler, William T.; Marr-Lyon, Mark; Rightley, Paul
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/02/2007
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The hydrodynamic operation of the `Forest Flyer' type of explosive launching system for shock physics projectiles was investigated in detail using one- and two-dimensional continuum dynamics simulations. The simulations were insensitive to uncertainties in the material properties, and reproduced measurements of the projectile. The most commonly-used variant, with an Al alloy case, was predicted to produce a slightly curved projectile, subjected to some shock heating, and likely exhibiting some porosity from tensile damage. The flatness can be improved by using a case of lower shock impedance, such as polymethyl methacrylate. High-impedance cases, including Al alloys but with denser materials improving the launching efficiency, can be used if designed according to the physics of oblique shock reflection. The tensile stress induced in the projectile depends on the relative thickness of the explosive, expansion gap, and projectile. The thinner the projectile with respect to the explosive, the smaller the tensile stress. If the explosive is initiated with a plane wave lens, the tensile stress is lower than for initiation with multiple detonators over a plane. The previous plane wave lens designs did however induce a tensile stress close to the spall strength of the projectile. The tensile stress can be reduced by changes in the component thicknesses. Experiments to verify the operation of explosively-launched projectiles should attempt to measure porosity induced in the projectile: arrival time measurements may be insensitive to porous regions caused by damaged or recollected material.

Dynamic fracture of inorganic glasses by hard spherical and conical projectiles

Chaudhri, M. Munawar
Fonte: Royal Society Publishing Publicador: Royal Society Publishing
Tipo: Article; accepted version
EN
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This is the accepted manuscript of a paper published in Philisophical Transactions A., 373: 20140135. http://dx.doi.org/10.1098/rsta.2014.0135; In this article, high-speed photographic investigations of the dynamic crack initiation and propagation in several inorganic glasses by the impact of small spherical and conical projectiles are described. These were carried out at speeds of up to approximately 2 ? 106 frames s?1. The glasses were fused silica, ?Pyrex? (a borosilicate glass), soda lime and B2O3. The projectiles were 0.8?2 mm diameter spheres of steel, glass, sapphire and tungsten carbide, and their velocities were up to 340 m s?1. In fused silica and Pyrex, spherical projectiles? impact produced Hertzian cone cracks travelling at terminal crack velocities, whereas in soda-lime glass fast splinter cracks were generated. No crack bifurcation was observed, which has been explained by the nature of the stress intensity factor of the particle-impact-generated cracks, which leads to a stable crack growth. Crack bifurcation was, however, observed in thermally tempered glass; this bifurcation has been explained by the tensile residual stress and the associated unstable crack growth. A new explanation has been proposed for the decrease of the included angle of the Hertzian cone cracks with increasing impact velocity. B2O3 glass showed dynamic compaction and plasticity owing to impact with steel spheres. Other observations...

Nano-biolistics: a method of biolistic transfection of cells and tissues using a gene gun with novel nanometer-sized projectiles

O'Brien, John A; Lummis, Sarah C R
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Artigo de Revista Científica
EN
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RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.; Abstract Background Biolistic transfection is proving an increasingly popular method of incorporating DNA or RNA into cells that are difficult to transfect using traditional methods. The technique routinely uses 'microparticles', which are ~1 ?m diameter projectiles, fired into tissues using pressurised gas. These microparticles are efficient at delivering DNA into cells, but cannot efficiently transfect small cells and may cause significant tissue damage, thus limiting their potential usefulness. Here we describe the use of 40 nm diameter projectiles - nanoparticles - in biolistic transfections to determine if they are a suitable alternative to microparticles. Results Examination of transfection efficiencies in HEK293 cells, using a range of conditions including different DNA concentrations and different preparation procedures...

Measurements of the High Frequency Noise Produced by Cavitating Projectiles in the High Speed Water Tunnel

Knapp, Robert T.
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em 31/08/1943
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The High Speed Water Tunnel is operated by the California Institute of Technology under Contract OEMsr-207 and is sponsored by Division 6, Section 6.1 of the NDRC of the OSRD. The experiments reported in this memorandum were requested by the office of the Chief of Section 6.1. The report presents the results of preliminary measurements of the sound produced in the 20 to 100 kilocycle frequency range by cavitating projectiles in the Water Tunnel working section. Measurements were made of the noise intensity in the 20-100 kilocycle frequency band with three different projectiles. Measurements of the intensity and distribution of the noise within this band were made with one of these projectiles.