The whistler nozzle phenomenon

The whistler nozzle is a simple device which can induce jet self-excitations of controllable amplitudes and frequencies and appears highly promising for many applications involving turbulent transport, combustion and aerodynamic noise. The characteristics of this curious phenomenon are documented for different values of the controlling parameters and attempts to explain the phenomenon. It is shown that the whistler excitation results from the coupling of two independent resonance mechanisms: shear-layer tone resulting from the impingement of the pipe-exit shear layer on the collar lip, and organ-pipe resonance of the pipe-nozzle. The crucial role of the shear-layer tone in driving the organ-pipe resonance is proven by reproducing the event in pipe-ring and pipe-hole configurations in the absence of the collar. It is also shown that this phenomenon is the strongest when the self-excitation frequency matches the preferred mode of the jet

Charged gravastars admitting conformal motion

We propose a new model of a {\it gravastar} admitting conformal motion. While retaining the framework of the Mazur-Mottola model, the gravastar is assumed to be internally charged, with an exterior defined by a Reissner-Nordstr{\"o}m rather than a Schwarzschild line element. The solutions obtained involve (i) the interior region, (ii) the shell, and (iii) the exterior region of the sphere. Of these three cases the first case is of primary interest since the total gravitational mass vanishes for vanishing charge and turns the total gravitational mass into an {\it electromagnetic mass} under certain conditions. This suggests that the interior de Sitter vacuum of a charged gravastar is essentially an electromagnetic mass model that must generate the gravitational mass. We have also analyzed various other aspects such as the stress energy tensor in the thin shell and the entropy of the system.Comment: Minor addition, Accepted in Phys. Lett.

Direct simulation for a homogenous gas

A probabilistic analysis of the direct simulation of a homogeneous gas is given. A hierarchy of equations similar to the BBGKY hierarchy for the reduced probability densities is derived. By invoking the molecular chaos assumption, an equation similar to the Boltzmann equation for the single particle probability density and the corresponding H-theorem is derived

Pertanggungjawaban Orang Tua Terhadap Anak Incest Menurut Hukum Islam

Based on the Islamic criminal law, the incest performer is handed down a death sentence as referred to Prophet Muhammad's words retold by Abdullah Bin Abbas ‘whoever has a sexual intercourse with his mahram (immediate/close relative), kill him”. The parents are responsible for their children in line with Al-Quran Surah i.e. Al-Baqarah, verse 233. One of the parents' responsibilities for their incestuous child's is to provide the custody. Based on the Islamic law, the custody of the incestuous child is given to his/her mother. In case she cannot take care of the child because she is not eligible for the custody; according to the Islamic law, it is transferred to his/her mother's relatives. An incestuous child does not have a kinship (nasab Consequently, based on the Islamic inheritance law, an incestuous child does not have any rights on the inheritance left by his/her father. However, according to Imam Syafi'i in the Compilation of the Islamic Laws Article 186, an incestuous child has the inheritance relationship from his/her mother and relatives from his/her mother side

Inelastic X-ray scattering in correlated (Mott) insulators

We calculate the inelastic light scattering from X-rays, which allows the photon to transfer both energy and momentum to the strongly correlated charge excitations. We find that the charge transfer peak and the low energy peak both broaden and disperse through the Brillouin zone similar to what is seen in experiments in materials like Ca_2 Cu O_2 Cl_2.Comment: 5 pages Revtex4, 6 figure

Towards the Formal Reliability Analysis of Oil and Gas Pipelines

It is customary to assess the reliability of underground oil and gas pipelines in the presence of excessive loading and corrosion effects to ensure a leak-free transport of hazardous materials. The main idea behind this reliability analysis is to model the given pipeline system as a Reliability Block Diagram (RBD) of segments such that the reliability of an individual pipeline segment can be represented by a random variable. Traditionally, computer simulation is used to perform this reliability analysis but it provides approximate results and requires an enormous amount of CPU time for attaining reasonable estimates. Due to its approximate nature, simulation is not very suitable for analyzing safety-critical systems like oil and gas pipelines, where even minor analysis flaws may result in catastrophic consequences. As an accurate alternative, we propose to use a higher-order-logic theorem prover (HOL) for the reliability analysis of pipelines. As a first step towards this idea, this paper provides a higher-order-logic formalization of reliability and the series RBD using the HOL theorem prover. For illustration, we present the formal analysis of a simple pipeline that can be modeled as a series RBD of segments with exponentially distributed failure times.Comment: 15 page

Adjustment of a Coastal Buoyant Outflow Under Tidal and Wind Forcing

The discharge of brackish water from estuaries typically forms distinct coastal plumes, often visible through their color signature due to sediment load and particulate matter from rivers. The processes of mixing and dispersion of coastal plumes are subjected to natural variations in the magnitude and timing of freshwater inflows, tides and meteorological conditions. This study presents shipboard observation of the bulge region of a buoyant plume off Winyah Bay, SC. The observation comprises downward looking 600 and 1200 kHz ADCP (Acoustic Doppler Current Profiler) and CTD measurements. Along with standard CTD casts, water samples were collected to analyze and determine mass sediment concentration using standard filtering techniques. Auxiliary data such as wind, river discharge and coastal sea level measurements were collected from WeatherFlow, USGS streamflow and NOAA tide gauge stations, respectively. The study addresses the evolution of bulge region of the plume under the conditions of low freshwater discharge and light wind forcing. The study also examines the fate of the suspended sediments under high discharge condition. The spatial and temporal salinity and temperature structures from CTD measurements are analyzed to inspect the evolution of the bulge region. The impact of suspended sediments on modifying the density anomaly within the plume is also assessed. Gradient Richardson number is calculated to examine the influence of suspended sediments on the mixing processes within the plume. Analysis of the observations demonstrate that the buoyant water was not dispersed by the wind forcing but formed a well pronounced baroclinic jet with associated front. The buoyant outflow occurring at semidiurnal tidal frequency first propagated northward with the wind-driven currents, but then turned anticyclonically and continued southward, against the wind-driven current. However, this baroclinic jet never reached the coastline to form a coastal current. Due to wind forcing, the frontal zone width exceeded the baroclinic Rossby radius, and in some cases multiple frontal structures were observed. Overall, the results demonstrate that under certain forcing conditions all buoyant outflow is deflected into a growing bulge and ultimately spreads offshore contributing to the cross-shelf exchange processes

Comparison of double disc and combined disc method for the detection of extended spectrum beta lactamases in enterobacteriaceae

Objective: To compare double disc approximation and combined disc method for their ability to detect extended spectrum b lactamase (ESBL) production in enterobacteriaceae and determine the percentage of isolates which are falsely reported as sensitive in absence of ESBL detection, in a clinical microbiology laboratory of a tertiary care hospital between September-October 2002. Methods: Selected isolates were identified according to standard biochemical tests. Disc susceptibility tests were performed according to NCCLS. ESBL detection by combined disc [cefotaxime (30 ug) versus cefotaxime plus clavulanate (30+10 ug)] was compared with detection using double discs [amoxy-clavulanic acid (20+10 ug) and aztreonam (30 ug) applied 10 mm apart]. Results were interpreted according to NCCLS and analysed on SPSS version 10. Results: ESBL production was detected in 140 (30%) isolates by combined disc method and 139 (29.5%) by double disc method. There was no significant difference between two methods. Of the ESBL positive isolates 41 (29%) gave zone diameters that were within the sensitivity range cutoff and would have been falsely reported as being beta lactam sensitive in absence of ESBL detection. Conculsion: ESBL detection should be routinely performed in clinical laboratories as false reporting would result in treatment failure despite in vitro sensitivity. No difference was found between the combined disc and double disc methods hence either of two could be used

Pemanfaatan Serbuk Kaca Sebagai Bahan Tambah Agregat Halus Untuk Meningkatkan Kuat Tekan Beton

Concrete is a building which is composed by an aggregate (sand rocks), cement and water (plus the other ingredients can be additive or admixture). Much research has been done on the concrete technology to meet the needs in infrastructure development started from the street, buildings, bridges, etc. The more concrete and more widespread use of the increasing scale of development also shows the more concrete needs in the foreseeable future, thus affecting the development of concrete technology which will demand new innovations regarding the concrete itself The times in the era of globalization, this resulted in a rapid increase of the number of goods waste residu which existence can be a problem for life, one of which is the presence of household glass waste. In this regard the efforts made are the utilization of powder glass as fine aggregate additive to enhance strong press concrete. Glass powder is used as a supplement for is smooth, with the addition of different variations, it is hoped to provide strong value press the concrete which is more varied and can be determined the optimum levels of glass powder. As for the variation of the addition of powder glass used is 0 %, 25 %, 50 %, 75 %, and 100 %, with tests on a 3-day, 7-day, 14-day and 28 days. The result shows that glass powder can increase the strength of the concrete of compressive strength of concrete press 12 % normal, whereas for the optimum proportion is 25%