Search results for "Piston"
showing 10 items of 108 documents
"Melko onnellinen puhallinorkesteri" : tapaustutkimus Jyväskylän yliopiston puhallinorkesterista
2010
Tutkielman tavoitteena oli selvittää puhallinorkesterissa soittamisen merkitystä soittajalle sosiaalisena tapahtumana, sekä orkesteriharrastuksen eroja kuoroharrastukseen yhdessä olemisen muotona. Kuoroharrastuksen on todettu olevan erittäin merkittävä asia elämässä sitä harrastavalle, ja tämän tutkielman tarkoitus on tarkastella orkesteriharrastusta samasta näkökulmasta. Tutkielma toteutettiin tapaustutkimuksena, ja sen aineisto kerättiin verkossa täytettävän kyselyn avulla Jyväskylän yliopiston puhallinorkesteri Puhkupillien soittajilta syksyn 2009 aikana. Kysely toteutettiin pääpiirtein samanlaisena myös Musica-kuorolle, ja näin saatiin vertailukelpoisia tuloksia kuorosta sekä orkesteris…
Acoustic Emission-Based Condition Monitoring and Remaining Useful Life Prediction of Hydraulic Cylinder Rod Seals
2021
The foremost reason for unscheduled maintenance of hydraulic cylinders in industry is caused by wear of the hydraulic seals. Therefore, condition monitoring and subsequent estimation of remaining useful life (RUL) methods are highly sought after by the maintenance professionals. This study aimed at investigating the use of acoustic emission (AE) sensors to identify the early stages of external leakage initiation in hydraulic cylinders through run to failure studies (RTF) in a test rig. In this study, the impact of sensor location and rod speeds on the AE signal were investigated using both time- and frequency-based features. Furthermore, a frequency domain analysis was conducted to investig…
Pressure dependence of density and structural relaxation of glass near the glass transition region
2017
International audience; A simplified and effective pressure cell together with an experimental procedure has been developed and applied to compress samples of SCHOTT N-BK7 glass under static high pressures in a piston-cylinder apparatus. Results from the density and volume recovery measurements show that, the glass samples were effectively densified in piston-cylinder apparatus with the density at room temperature increasing linearly with frozen-in pressure. To explain the experimental data, we developed a mathematical model based on a suggestion by Gupta (1988) with two internal parameters, named fictive temperature (Tf) and fictive pressure (Pf), which fits the experimental data well.
NELLI vie tiedonlähteille
2006
Pressure-flow dynamics with semi-stable limit cycles in hydraulic cylinder circuits
2021
In hydraulic circuits of the standard fluid-power actuators and mechanisms, like the linear-stroke cylinders, some hydrodynamic effects are often neglected. It happens mainly due to their complexity and secondariness in comparison with the principal transient and steady-state behavior of the hydromechanical process variables, such as the differential pressure and relative displacement and its rate, in other words the piston stroke and velocity. However, a constrained motion of the cylinder piston can give rise to the back coupled excitation of the pressure-flow dynamics, especially upon mechanical impact at the cylinder limits. Following to that, semi-stable limit cycles can arise while the…
Hydrodynamic description of the adiabatic piston.
2006
A closed macroscopic equation for the motion of the two-dimensional adiabatic piston is derived from standard hydrodynamics. It predicts a damped oscillatory motion of the piston towards a final rest position, which depends on the initial state. In the limit of large piston mass, the solution of this equation is in quantitative agreement with the results obtained from both hard disk molecular dynamics and hydrodynamics. The explicit forms of the basic characteristics of the piston's dynamics, such as the period of oscillations and the relaxation time, are derived. The limitations of the theory's validity, in terms of the main system parameters, are established.
The escape transition of a compressed star polymer: Self-consistent field predictions tested by simulation
2013
The escape transition of a polymer "mushroom" (a flexible chain grafted to a flat non-adsorbing substrate surface in a good solvent) occurs when the polymer is compressed by a cylindrical piston of radius $R$, that by far exceeds the chain gyration radius. At this transition, the chain conformation abruptly changes from a two-dimensional self-avoiding walk of blobs (of diameter $H$, the height of the piston above the substrate) to a "flower conformation", i.e. stretched almost one-dimensional string of blobs (with end-to-end distance $\approx R$) and an "escaped" part of the chain, the "crown", outside the piston. The extension of this problem to the case of star polymers with $f$ arms is c…
(Table 1) Sea surface temperature reconstruction for eastern equatorial Pacific surface sediment samples
2012
Significant uncertainties persist in the reconstruction of past sea surface temperatures in the eastern equatorial Pacific, especially regarding the amplitude of the glacial cooling and the details of the post-glacial warming. Here we present the first regional calibration of alkenone unsaturation in surface sediments versus mean annual sea surface temperatures (maSST). Based on 81 new and 48 previously published data points, it is shown that open ocean samples conform to established global regressions of Uk'37 versus maSST and that there is no systematic bias from seasonality in the production or export of alkenones, or from surface ocean nutrient concentrations or salinity. The flattening…
Prahan kevät 2008 : Kaarlen yliopiston kirjastoihin tutustumassa
2008
Modeling of Friction Losses in Offshore Knuckle Boom Crane Winch System
2018
This paper presents a method for friction modeling in a hydraulically actuated multi motor winch system of an offshore knuckle boom crane. The method is based on a combination of a model of the variable displacement axial piston motor based on measurements from the sub supplier, and combined with a model of the remaining friction loss obtained from measurements on the full system.