Absorption of laser radiation in a laser-produced plasma of Xe – hydrodynamic effects and nonequilibrium ionization

Experiments on measuring absorption of an IR laser radiation in the laser-produced plasma of Xe are described. The absorbed fraction of up to 65% has been obtained when the gas-jet target was illuminated by a wide, defocused beam, whereas it barely reached 8.5% in the case of a sharply focused beam. The phenomenon is explained on the basis of a hypothesis of the plasma hydrodynamic expansion according to which the plasma leaves the illuminated area the faster, the smaller its size. Based on the experimental results, an attempt to estimate plasma parameters (N, T, <Z>) is undertaken, with the mean ion charge, <Z>, being calculated using ionization cross-sections for ions from +7Xe to +14Xe which were obtained by means of a quantum-mechanical numeric simulation especially for the present work. A similarity of the EUV output and the laser energy absorption as functions of the laser beam diameter needs an additional study in a future.

Initial study of an alternative technology aimed at measuring and controlling the flow rate in air conditioning ducts

This paper states that there might have around 1000 small size business jets (until nine occupants) flying across the world equipped with flow control and regulating shut-off valves that uses hot wire anemometer devices to regulate massflow rate from the bleed airflow to supply the air-conditioning and pressurization systems. However, these valves present low reliability in the field. The purpose of this paper is to evaluate the implications of a flow control and regulating shut-off valve with a non-intrusive airflow measurer device under the perspective of fluid mechanics. The Venturi technology that is commonly used technology, given its construction simplicity, precision, and broad use in the industry, is selected to substitute the flow control and regulating shut-off valves with hot wire anemometer of the mentioned small size business jets applications. This paper has adopted a numeric simulation approach utilizing the ANSYS-CFX computational fluid dynamics software to verify both the differential pressure at the Venturi device and its correspondent mass flow rate to supply the air conditioning systems of some small size business jets, considering the mass-flow rate as requested by the FAA certification requirement (0.55 lb/min per occupant). This paper shows that a mass-flow rate control and regulating shut-off valve with a Venturi device, of 1 inch and β of 0.67, is compliant with the minimum fresh air flow requested by the FAA certification requirement to operate in some small size business jets. Besides that, the software ANSYS-CFX is also effective to support the engineering analysis of flow field characteristics inherent to the applications of internal compressible flow. The numeric simulation utilizing the ANSYS-CFX computational fluid dynamics software outlined herein can lay the basis for further research related to the design of a flow control and regulating shut-off valves with a Venturi device.

Numeric Simulation Demonstrates That the Upstream Movement of Invasive Bigheaded Carp Can Be Blocked at Sets of Mississippi River Locks-and-Dams Using a Combination of Optimized Spillway Gate Operations, Lock Deterrents and Carp Removal

Invasive bigheaded carp are advancing up the Upper Mississippi River by passing through its locks-and-dams (LDs). Although these structures already impede fish passage, this role could be greatly enhanced by modifying how their spillway gates operate, adding deterrent systems to their locks, and removing carp. This study examined this possibility using numeric modeling and empirical data, which evaluated all three options on an annual basis in both single LDs and pairs under different river flow conditions. Over 100 scenarios were modeled. While all three approaches showed promise, ranging from 8 to 73% reductions in how many carp pass a single LD, when employed together at pairs of LDs, upstream movement rates of invasive carp could be reduced 98–99% from current levels. Although modifying spillway gate operation is the least expensive option, its efficacy drops at high flows, so lock deterrents and/or removal using fishing/trapping are required to move towards complete blockage. Improved deterrent efficacy could also offset the need for more efficient removal. This model could help prioritize research and management actions for containing carp.

Synchronized Motion Profiles for Inverse-Dynamics-Based Online Control of Three Inextensible Segments of Trunk-Type Robot Actuators

This study proposes a novel method for the positioning and spatial orientation control of three inextensible segments of trunk-type robots. The suggested algorithm imposes a soft constraint assumption for the end-effector’s endpoint and a mandatory constraint on its direction. Simultaneously, the algorithm by-design enforces nonholonomic features on the robot segments in the form of arcs. An approximate robot spine curve is the key to the final robot state configuration based on the given conditions. The numeric simulation showed acceptable (less than 1 s) performance for single-core processing tasks. The parametric method finds the best proximate robot state solution and represents the gray box model in addition to existing learning or black-box inverse dynamics approaches. This study also shows that a multiple inverse kinematics answer constructs a single inverse dynamics solution that defines the robot actuators’ motion profiles, synchronized in time. Finally, this text presents rotational expressions and their outlines for controlling the manipulator’s tendons.

A Matching Problem between the Front Fan and Aft Fan Stages in Adaptive Cycle Engines with Convertible Fan Systems

In the process of studying the steady-state performance and component matching of adaptive cycle engines with convertible fan system, it was found that the front fan and aft fan stage have a unique matching problem when the mode select valve is closed and engine is operating at higher Mach number conditions. The cause of this matching problem was studied with numeric simulation in this paper. Based on the features of adaptive cycle engines with convertible fan system, the possible methods and their feasibilities of solving this matching problem were also discussed. According to the results, the flow rate adjustment capacity of the aft fan stage directly determines the occurrence and severity of this matching problem. The matching problem can be ameliorated in some extent by either reducing the design second bypass ratio or adjusting the variable geometry mechanisms, but it cannot be completely solved at the aspect of component matching mechanism.

Numeric simulation of the pulsation bottle for a reciprocating compressor in dynamic regime

The pulsation bottles are mounted at the inlet and outlet of / from the reciprocating compressor cylinders to even out the gas parameters (pressure and temperature). They ensure stable working conditions in the compressor cylinders and eliminate / reduce vibrations. The sizing of the pulsation bottle is done based on the geometric parameters of the compressor, the volume efficiency and working pressure. The use of a dynamic model made in the LMS Amesim program allows the study of a compressor with a set of pulsation bottles at the modification of: the pressure and temperature at the inlet / outlet of the compressor, the speed of the compressor the volume of the dead space and blocking or removing of the valves. The model includes the compressor cylinder with the corresponding dead spaces, the compressor valves, the suction and discharge pipelines and crank connecting rod mechanism. The simulation takes into account of the: gas composition, temperature and pressure in the system. The variation of the pressure in the bottles can be checked under these conditions. The values of the disturbing forces for a range of working and adjustment parameters can be obtained, values that can be used in a dynamic analysis according to API 618.