Unsteady transonic flow in cascades

There is a need for methods to predict the unsteady air loads associated with flutter of turbomachinery blading at transonic speeds. The results of such an analysis in which the steady relative flow approaching a cascade of thin airfoils is assumed to be transonic, irrotational, and isentropic is presented. The blades in the cascade are allowed to undergo a small amplitude harmonic oscillation which generates a small unsteady flow superimposed on the existing steady flow. The blades are assumed to oscillate with a prescribed motion of constant amplitude and interblade phase angle. The equations of motion are obtained by linearizing about a uniform flow the inviscid nonheat conducting continuity and momentum equations. The resulting equations are solved by employing the Weiner Hopf technique. The solution yields the unsteady aerodynamic forces acting on the cascade at Mach number equal to 1. Making use of an unsteady transonic similarity law, these results are compared with the results obtained from linear unsteady subsonic and supersonic cascade theories. A parametric study is conducted to find the effects of reduced frequency, solidity, stagger angle, and position of pitching axis on the flutter

Influence of Hydrodynamic Interactions on the Kinetics of Colloidal Particle's Adsorption

The kinetics of irreversible adsorption of spherical particles onto a flat surface is theoretically studied. Previous models, in which hydrodynamic interactions were disregarded, predicted a power-law behavior $t^{-2/3}$ for the time dependence of the coverage of the surface near saturation. Experiments, however, are in agreement with a power-law behavior of the form $t^{-1/2}$. We outline that, when hydrodynamic interactions are considered, the assymptotic behavior is found to be compatible with the experimental results in a wide region near saturation.Comment: 4 pages, 1 figures, Phys. Rev. Lett. (in press

The rapidity dependence of the proton-to-pion ratio in Au+Au and p+p collisions at sqrt(sNN) = 62.4 and 200 GeV

The BRAHMS measured proton-to-pion ratios in Au+Au and p+p collisions at \rootsnn{62.4} and \rootsnn{200} are presented as a function of transverse momentum and collision centrality within the pseudo-rapidity range 0 < eta < 3.8 The results for Au+Au at sqrt(sNN) = 200 GeV are compared with predictions from models which incorporate hydro-dynamics, hadron rescattering and jet production, in the eta interval covered. In Au+Au collisions at sqrt(sNN) = 200 GeV, eta ~ 2.2, and at sqrt(sNN) = 62.4 GeV, eta = 0, the bulk medium can be characterized by the common value of \mi_B ~ 65 MeV. The p/pi ratios measured for these two selections display a striking agreement in the pT range covered (up to 2.2 GeV/c). At a collision energy of 62.4 GeV and at forward pseudo-rapidity we found a crossing point of p/pi+ ratios measured in central and semi-peripheral Au+Au and in p+p reactions. The crossing occurs in the narrow eta bin around value of 3.2, simultaneously in the whole covered pT range (0.3 GeV/c < pT < 2 GeV/c).Comment: 4 pages, 4 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee Included corrections indicated in internal review report. Minor correction to Fig.

Comparison of Grain Refinement in Selected Materials Subjected to Hydrostatic Extrusion

The subject of this study was to examine and compare the impact of intense hydrostatic extrusion on grain refinement in three different alloys: duplex stainless steel, commercially used aluminum alloy (6060) and Ag-Cu12 alloy. As a result of the process grain sizes from 370 nm to 90 nm were obtained in aluminum and duplex steel. To analyze the of hydrostatic on mechanical properties tensile tests were also carried out. The highest grain refinement (70 nm) and yield strength increase (over 300%) was observed in duplex steel af-ter hydrostatic extrusion. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3560

Utilization of parallel processing in solving the inviscid form of the average-passage equation system for multistage turbomachinery

A procedure is outlined which utilizes parallel processing to solve the inviscid form of the average-passage equation system for multistage turbomachinery along with a description of its implementation in a FORTRAN computer code, MSTAGE. A scheme to reduce the central memory requirements of the program is also detailed. Both the multitasking and I/O routines referred to are specific to the Cray X-MP line of computers and its associated SSD (Solid-State Disk). Results are presented for a simulation of a two-stage rocket engine fuel pump turbine

Effects of ammonia on combustion, emissions, and performance of the ammonia/diesel dual-fuel compression ignition engine

Ammonia is currently receiving more interest as a carbon-free alternative fuel for internal combustion engines (ICE). A promising energy carrier, easy to store and transport, being liquid, and non-carbon-based emissions which make ammonia a green fuel to decarbonize ICE and to reduce greenhouse gas (GHG) emissions. This paper aims to illustrate the impacts of replacing diesel fuel with ammonia in an ammonia/diesel dual fuel engine. Hence, the effects of various ammonia diesel ratios on emissions and engine performance were experimentally investigated. In addition, a developed 1D model is used to analyze the combustion characteristics of ammonia and diesel. Results show 84.2% of input energy can be provided by ammonia meanwhile indicated thermal efficiency (ITE) is increased by increasing the diesel substitution. Moreover, increasing the ammonia energy share (AES) changed the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Therefore, combustion duration and combustion phasing decreased by 6.8CAD and 32CAD, respectively. Although ammonia significantly reduced CO2, CO, and particulate matter (PM) emissions, it also increased NOX emissions and unburned ammonia (14800 ppm). Furthermore, diesel must be replaced with more than 35.9% ammonia to decrease GHG emissions, since ammonia combustion produces N2O (90 ppm) that offsets the reduction of CO2.<br/

Effects of ammonia on combustion, emissions, and performance of the ammonia/diesel dual-fuel compression ignition engine

Ammonia is currently receiving more interest as a carbon-free alternative fuel for internal combustion engines (ICE). A promising energy carrier, easy to store and transport, being liquid, and non-carbon-based emissions which make ammonia a green fuel to decarbonize ICE and to reduce greenhouse gas (GHG) emissions. This paper aims to illustrate the impacts of replacing diesel fuel with ammonia in an ammonia/diesel dual fuel engine. Hence, the effects of various ammonia diesel ratios on emissions and engine performance were experimentally investigated. In addition, a developed 1D model is used to analyze the combustion characteristics of ammonia and diesel. Results show 84.2% of input energy can be provided by ammonia meanwhile indicated thermal efficiency (ITE) is increased by increasing the diesel substitution. Moreover, increasing the ammonia energy share (AES) changed the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Therefore, combustion duration and combustion phasing decreased by 6.8CAD and 32CAD, respectively. Although ammonia significantly reduced CO2, CO, and particulate matter (PM) emissions, it also increased NOX emissions and unburned ammonia (14800 ppm). Furthermore, diesel must be replaced with more than 35.9% ammonia to decrease GHG emissions, since ammonia combustion produces N2O (90 ppm) that offsets the reduction of CO2.<br/

Urological procedures in Central Europe and the current reality based on the national registries of Czech Republic, Hungary, and Poland (2012 status)

INTRODUCTION: In recent years, the laparoscopic approach in oncologic urology seems more attractable to the surgeons. It is considered to have the same oncologic quality as open surgery, but is less invasive in patients. It is used widely in all of Europe, but with various frequency. The aim of the study was to present a various amount of oncourological procedures from three neighbouring countries - Poland, Czech Republic and Hungary. Prostatectomy, cystectomy, nephrectomy and tumorectomy (Nephron Sparing Procedures - NSS) were presented as a list of procedures prepared from the national registry. MATERIAL AND METHODS: The total amount of procedures was presented, as well as the LO (Lap to Open procedures) index, P/P (procedures/population) index, ratio of cystectomy/population, and cystectomy/TURBT. RESULTS: In the Czech Republic, the most complex procedures are performed (laparoscopic/robotic prostatectomy, NSS LAP, LAP nephrectomy) in the majority when analysing the country's population. In Hungary and Czech Republic, there are more laparoscopic/robotic radical prostatectomies performed, than open ones. In Poland the largest number of cystectomies is performed when analysing the country's population, but it is difficult to explain the much higher ratio of 6.57 TUR/one cystectomy. In the Czech Republic this procedure is performed in almost one quarter of the patients (23.36%). Interestingly, in Hungary the cystectomy with pouch creation is performed in about 67.65% cases. The highest reimbursement for surgical procedure is present in the Czech Republic with approximately 20-40% more than when compared to Poland or Hungary. CONCLUSIONS: The definitive leader in Central Europe (based on the national registry) is the Czech Republic, where the most complex procedures are performed (laparoscopic/robotic prostatectomy, NSS LAP, LAP nephrectomy) in biggest amounts when analysing the country's population. Explanation of such circumstances, can be the higher reimbursement rate for surgical procedure in this country

Model of correlated sequential adsorption of colloidal particles

We present results of a new model of sequential adsorption in which the adsorbing particles are correlated with the particles attached to the substrate. The strength of the correlations is measured by a tunable parameter $\sigma$. The model interpolates between free ballistic adsorption in the limit $\sigma\to\infty$ and a strongly correlated phase, appearing for $\sigma\to0$ and characterized by the emergence of highly ordered structures. The phenomenon is manifested through the analysis of several magnitudes, as the jamming limit and the particle-particle correlation function. The effect of correlations in one dimension manifests in the increased tendency to particle chaining in the substrate. In two dimensions the correlations induce a percolation transition, in which a spanning cluster of connected particles appears at a certain critical value $\sigma_c$. Our study could be applicable to more general situations in which the coupling between correlations and disorder is relevant, as for example, in the presence of strong interparticle interactions.Comment: 6 pages, 8 EPS figures. Phys. Rev. E (in press

Notifications Efficiency, Impact, and Interference in Second-Screen Scenarios

The growing use of second-screen devices stresses the importance of finding a balance between engagement, distraction, and disturbance of its users, while simultaneously watching television. In this framework, this article reports on a study designed to analyze the efficiency, impact, and interference of different notification strategies aiming to identify the best approach to be used when an alert is needed in second-screen scenarios. A prototype able to deliver synchronized information related with TV content, with intervals of 10, 30 and 60 s, followed by individual or combined notifications (e.g., audio, visual, and haptic—on the tablet and visual—on the TV) was developed. A laboratory adapted to replicate a living room was set up and a test that involved watching three segments of a 20-min clip while using the prototype was carried with 30 participants, under a cognitive walk-through protocol. Quantitative and qualitative results show that receiving notifications while watching TV is effective in alerting users about new information, despite its inherent cognitive disturbance for the TV viewing experience. It was also possible to highlight that in an HCI perspective, the most suitable strategy for integrating notifications (considering type and cadence) should be based on a combination of a visual notification (displayed only on the TV screen) along with a haptic notification (vibration on the tablet); spaced by an interval of at least 30 s