Dominant Portion Research Articles

Contaminating effect of probe noise on jet pressure correlations

When a fast-responding static pressure probe is inserted into a flow, there are several possible mechanisms for the generation of extraneous noise. If the probe signal is cross correlated with the farfield sound, then the ’’probe noise’’ may contribute a dominant portion of the total correlatable noise from the local source region. A theoretical model is developed for predicting the distortion of ’’causality’’ correlation signatures (obtained when in-flow probes are cross correlated with the farfield sound), due to the parasitic probe noise. The predicted correlation functions agree with experiments conducted using probes of various shapes and sizes. In practice, the contaminated portion of the causality correlation signature is expected to be displaced in time from the ’’true’’ jet pressure correlation. An unexpected result of the present experiments is the absence of any legitimate correlation between the turbulent pressure fluctuations and the farfield jet noise. This leads to the conclusion that the extent and strength of the jet pressure fluctuations as noise sources must be very weak. Therefore, any probing device inserted into the flow will generally produce a large and potentially misleading portion of the total correlation.

Flow field and acoustic properties of a Mach number 0·9 jet at a low Reynolds number

An experimental study of the flow field and acoustic properties of a low Reynolds number ( Re ≅ 3600), M = 0·9 jet has been performed in our low pressure anechoic test chamber. The mean flow field was surveyed with a conventional Pitot pressure probe and flow fluctuations were detected with a normal hot wire probe. Also, condenser microphone measurements were made in the acoustic field. The major goal of the study was to develop a better understanding of the noise generation mechanisms of subsonic jets. The flow fluctuations within the jet were found to be dominated initially by a relatively discrete, large-scale, wave-like instability centered around a Strouhal number of 0·44. The axial wavelength of this instability was determined to be 1·45 jet diameters and its azimuthal character includes the n = 0 and n = ± 1 modes. The growth of this instability coupled with its non-linear breakdown are major contributors to the termination of the potential core region of the jet. The acoustic field of the jet, in contrast to the flow field, has a broad frequency spectrum with a peak amplitude near a Strouhal number of St = 0·2. The results indicate that a non-linear mechanism involving the large scale flow instability is responsible for a dominant portion of the noise generated from this jet.

The Safe Time Limit of Temporary Clamping of Cerebral Arteries in the Direct Surgical Treatment of Intracranial Aneurysm under Moderate Hypothermia

Of 274 operated cases of cerebral aneurysm, temporary occlusion of the cerebral arteries was used in 215 cases (79%). Of the 215 cases, 177 (82%) showed no sequelae. The maximum safe time limit for temporary occlusion at the bilateral A1 portion of the anterior cerebral arteries was 48.5 min at 26 degrees C, 47 min at 27 degrees C, and 42 min at 28 degrees C; at the M1 portion of the middle cerebral arteries, it was 30 min at 26 degrees C, 35 min at 27 degrees C, 36 min at 27.5 degrees C, 40 min at 30 degrees C and 19 min at normothermia; and at the dominant A1 portion, in cases of hypoplasia at the contralateral A1 portion, it was 82 min at 26 degrees C, 86 min at 27.5 degrees C, and 63 min at 28 degrees C. Consequently, when performing direct surgery on aneurysms of the anterior communicating artery, unilateral clamping of the A1 portion prevents rupture during surgery and has the advantage of prolonging the occlusion time. Neurological sequelae may have been caused by the temporary occlusion of the cerebral artery in one case, and by the temporary occlusion or the surgical operation in six cases. Of the 22 fatal cases, only one was thought to be due to the temporary occlusion of the cerebral artery. Intermittent release of the clamping for 5 to 10 min is considered to be effective in prolonging the safe time limit of temporary clamping of the cerebral arteries in surgery of cerebral aneurysm under moderate hypothermia.

MALIGNANT TERATOMA OF THE THYROID GLAND IN AN ADOLESCENT FEMALE

Malignant teratoma of the thyroid gland was found in a 19-year-old female. She was given a combined surgical and irradiation treatment. The tumor was 5.0X4.0X3.6 cm and located in the lower right lobe of the thyroid gland. Light and electron microscopical examination revealed mature or immature derivatives of the three primordial germ layers. The dominant portion of the tumor was composed of numerous masses of cancerous epithelial cells, which were distributed randomly in the mesenchymal tissue. Tumor cells invaded and replaced the surrounding thyroid tissue with occasional tumor thrombi in the lumens of blood vessels. No metastatic tumor was found in the lymph nodes. The patient was given a course of external irradiation, a total dose of 4000 rads, to the right thyroid area. Eight months after surgery, she is well and without any evidence of recurrence or metastasis.

Reynolds Number Dependence in Supersonic Jet Noise

An experimental study of the noise production by high speed jets over a wide range of Reynolds numbers has been performed. Two jets of nominal Mach numbers 1.5 and 2.3 were run over a Reynolds number range from 5300 to 107,000. Microphone measurements of the radiated noise and hot-wire measurements of the flow fluctuations demonstrate that at low Reynolds numbers coherent flow instabilities produce a dominant portion of the noise. In the nominal Mach number 2.3 jet these instability waves convect downstream supersonically with respect to the ambient air. In the nominal Mach number 1.5 jet the instabilities convect downstream subsonically. In both cases however, sound pressure level amplitude contours show that the low Reynolds number jets radiate noise comparable to intermediate and high Reynolds number jets. These measurements constitute substantial evidence that a flow instability model of the dominant noise generators may be appropriate for conventional high Reynolds number supersonic jets. a0 C D d M m n r Re St u U Nomenclature speed of sound outside jet wavespeed in the downstream direction diameter of the jet effective diameter of the jet Mach number of the jet at the exit normalized mass velocity fluctuations = azimuthal mode number = radial distance from jet centerline = Reynolds number = p Ud/n. = Strouhal number =fd/ (/(/is frequency) = local velocity =mean centerline velocity of the jet at the nozzle exit

Parental Awareness and Attitudes of Digital Media Advertising to Children

Children today are very comfortable using electronic technology, Internet, on line games and digital platforms. The dominant portion of the on line content is consumed via their parent’s technological devices. Knowing that children are not able to recognize media content from intentional advertising, raises the complex question of whether and how Internet advertising can be regulated and how children can be protected. The negative implications of children’s exposure to on line advertising can be categorized in: financial and psychological, and are summarized but not limited to: obesity, anxiety paired with influence over domestic spending’s, psychological and ethical issues. This raises the complex question of whether and how Internet advertising can be regulated and how children can be protected from the negative implications. The majority of research are focused on institutional regulations and industrial limitations but the importance and the role of the parents as a regularity mechanism is underestimated. The theory recognizes that certain parental style differs on how they view online exposure of their children and that influence their role in the process on regulation children exposure on online advertising. From the other side digital literacy of the parents is very important milestone in the proses positioning the parents in a role of as a self-regulation mechanism of children exposure. The industry and the regulators should be alerted for this matter in all parts of the world, since this issue is rising negative implication.

Crystal Spectrum of the Rare-Earth Hexahalide Complexes, MCl63−: The Absorption Spectrum of [(C6H5)3PH]3NdCl6

The site symmetry of Nd3+ in single-crystal [(C6H5)3PH]3NdCl6 is predicted by considerations of molar absorptivity, vibronic spectra, and stoichiometry. A calculation of the crystalline-field splitting of 4f3 J levels appears to predict a sixfold octahedral site symmetry with a slight distortion along one of the axes, in agreement with the observed spectrum. In addition, the observed spectrum indicates the occurrence of two slightly inequivalent sites of Nd3+. The effects of the small distortion away from octahedral symmetry and the spectrum due to two inequivalent sites are sufficiently small (5% of the average J-manifold crystalline-field splitting), however, as not to affect a first-order crystal-field analysis of the dominant portion of the spectrum. The crystal-field parameters based on octahedral symmetry, B4 = 282 cm−1 and B6 = 74.7 cm−1, predict a splitting of crystal quantum states in good agreement with experiment.

Impulsively Loaded Strain-Rate-Sensitive Plates

The response of an impulsively loaded, isotropically rate-sensitive annular plate is calculated via “exact” and approximate viewpoints. For a typical example, numerical results differed by about 3 percent. The essence of the approximate approach, which represents a natural extension of a previous one-dimensional analysis [1], is that the initial stress profile remains substantially constant during the dominant portion of plastic flow.

Screening Corrections to the Fermi Function for AllowedβDecay

The influence of electron screening on the Fermi function $F(W,Z)$ for allowed $\ensuremath{\beta}$ decay is reconsidered. Numerical values for $F(W,Z)$ are obtained by integrating the radial Dirac equations for the decay electrons (positrons) in a self-consistent atomic potential. Relativistic Hartree-Fock-Slater equations are used to construct the atomic potential. The Fermi function is tabulated for various nuclei and energies, and comparisons are made with $F(W,Z)$ for a pure Coulomb field. Detailed comparisons are also made with the WKB screening formula of Rose as well as with the previous numerical results of Reitz and of B\uhring. It is found that the Rose formula provides an accurate approximation to $F(W,Z)$ over the dominant portion of the $\ensuremath{\beta}$ spectrum provided the endpoint energy is sufficiently high and provided further that an appropriate value of the potential at the nucleus ${V}_{0}$ is used. An empirical formula for ${V}_{0}$ from the Hartree-Fock-Slater calculations is provided. The numerical results of Reitz appear to be badly in error, especially for large electron momenta. The predictions of B\uhring for a screened-potential model are in good agreement with the present work. Corrections to the $\mathrm{ft}$ value of several superallowed Fermi transitions are recomputed and found to be negligibly different from the predictions made using the Rose approximation.

The Unsteady Loading on a Marine Propeller in a Nonuniform Flow

The lifting-surface integral equation governing the unsteady loading on a marine propeller in a nonuniform free stream is derived using a classical vortex model. The induced downwash is split into a part corresponding to a locally tangent flat finite wing and wake, plus parts corresponding to the effects of the "helicoidal deviation" from this, of the true blade and wake, and the interference from the other blades and their wakes. Strip-type approximations are tolerated on these terms while a lifting-surface formulation is retained for the dominant finite flat-wing portion. A simple numerical example is carried out and these effects are indeed found to be quite small; so small, in fact, that it may suffice to retain only the flat finite-wing terms in practical applications.