Due to the high speed of the air inside the combustion chamber of Scramjet engines, the proper mixing of fuel and air in the combustion chamber is one of the challenges and key issues in the design and analysis of such engines. To improve the mixing, various methods are used, including the implementation of a RAMP ahead of the injection port. In the present work, the effect of RAMP height on the area of double hydrogen jet cross-jet flow in supersonic airflow has been investigated numerically and the effect of RAMP height on parameters such as mixing efficiency, effective mixing area ratio and stagnation pressure losses has been investigated. Numerical simulations have been performed using the solution of the three-dimensional Reynolds-Averaged Navier-Stokes equations with the two-equation turbulence model k-ω,sst. Initially, the results of numerical solution were validated with the experimental data, which comparison of numerical solution results with experimental data shows their good agreement with each other. Then, the effect of the presence of a RAMP upstream of the injection port is numerically investigated for several RAMPs with different heights.

This paper studies the effects of queue formation in the bottlenecks at off-RAMPs on the capacity of the freeways. Six expressway exit-RAMPs throughout the city of Tehran, Iran were selected and their traffic flows were observed in thirty-minute intervals during which the queue formation and queue elimination occurred. Assuming that in the absence of the queue, the traffic flow is in its normal state, the changes in the volume of through vehicles has been modeled as an average estimator of the change in the expressway capacity.The developed models prove that the changes in freeway capacity are due to queue formation at the off-RAMP sections. However, the estimated figures are different from those obtained from the theory of freeway capacity. The conclusion is that lane blockage is only one of many factors that affect the freeway capacity while the queue forms. Since it is not possible to quantify all those factors individually, the resulting models are macroscopic estimates of the phenomenon.

Background: The prevalence of obesity is increasing worldwide, and anesthesiologists are facing challenges in the airway management of such patients. Excessive adipose tissue infl uences pharyngeal spaces and aff ects the laryngoscopic grade. Standard RAMP positioning is time-consuming and diffi cult to prepare, and requires expensive equipment. Objectives: The aim of this study was to compare the standard RAMP position with the proposed low-cost and easily accessible modifi ed RAMP position in laryngoscopic view during the intubation of patients with morbid obesity. Methods: In this single-blind clinical trial, 84 patients candidate for bariatric surgery at Rasoul Akram Hospital in 2020 were assigned to the rapid airway management positioner (RAMP) (R) and new modifi ed RAMP (MR) groups by the block randomization method. The laryngoscopic view of the glottis based on the Cormack-Lehane scale, ventilation quality, duration of intubation, intubation attempts, oxygen saturation at the end of intubation, and the need for backward, upward, rightward pressure (BURP) maneuver for successful intubation were recorded. Normal distribution tests and Mann-Whitney and Kruskal-Wallis tests were used to analyze the data. Results: The results showed no signifi cant diff erences between the two groups regarding ventilation score, laryngoscopy grade, number of intubation attempts, duration of intubation, and the need for BURP maneuvers during intubation (P > 0. 05). Conclusions: The two methods are not signifi cantly diff erent, and the new modifi ed RAMP position can be used with more ease and availability and less cost.

Based on Bessel-Thompson filter design method, a new procedure is introduced to determine a desired closed loop characteristic equation for the step input signal. The transient and steady state responses of the calculated system are similar to those of the CDM (Coefficient Diagram Method) controller. Using some properties from Laplace transform, the characteristic equation is then employed to obtain a new closed loop transfer function which results in appropriate response for the RAMP input signal. To evaluate the newly defined closed loop transfer function, a RST output feedback controller is designed and simulated.

SERN (Single Expansion RAMP Nozzle) nozzles often used in many aerospace vehicles with scramjet engines. Employment of SERN nozzles results in reducing the frictional drag and weight of nozzle and also they produce extra lift. A numerical study of supersonic gas flow in SERN nozzles is presented in this paper. The Navier-Stokes equations are solved with using a FORTRAN code. The governing equations are conservation of mass, momentums, energy and state equation of perfect gas for two dimensional compressible viscose flow. Equations are solved with using time-marching method. For verification, the results of recent numerical solution are compared with experimental results and results of Fluent and results of method of characteristics (MOC) and comparisons show good agreement with experimental results and other numerical solutions.

Block RAMPs are hydraulic structures which are commonly used in river restoration projects. Especially in the last few decades, the use of this type of structures have become more and more popular. They furnish a correct balance between the hydraulic functioning and the environmental care, as they minimize the impact on the environment in which they are located. In addition, they can be considered flexible structures, i.e. they can easily adapt to the in situ conditions and they can be easily built to re-convert traditional concrete structures. They can be built either by loose or fixed blocks, arranged on a sloped bed. However, a correct design of this structural typology has to take into consideration several aspects. In particular, the hydraulic functioning of a block RAMP is assured when the structure remains stable, i.e. when the blocks are not removed from their original position. Thus, the first step in designing block RAMPs has to be the structural stability. Furthermore, the analysis has to focus also on the dissipative process occurring on them, in particular it has to consider the different flow regimes that can take place and the effect of the bed roughness on the energy dissipation. Another important aspect is the stilling basin design. In fact, a block RAMP has not to be considered as an isolated element in the contest in which it is located. It is part of that contest and it contributes to modify it. Thus, it is extremely important to consider the scour process occurring downstream of the structure. In particular, the maximum scour depth and length have to be carefully estimated in order to avoid structural collapse of the RAMP. The scour process occurring downstream of the structure is also extremely important in terms of energy dissipation. In fact, the global dissipative process is the result of two distinct processes: one occurring on the RAMP and the other in the downstream stilling basin. Finally, the analysis has to take into consideration which are the global sediment transport conditions of the river in which the structure is located. Thus, it has to be conducted in both clear water and live-bed conditions. It appears evident that a correct design of this type of structures is a complex operation which requires a particular attention in order to avoid functioning problems.