scholarly journals Analysis of reservoir’s mass influence on the system free – surfaced liquid and spherical reservoir

2019 ◽  
pp. 110-113
Author(s):  
O. S. Limarchenko ◽  
Y. A. Sliusarchuk
Keyword(s):  
Normal Modes ◽  
Spherical Shape ◽  
Nonlinear Effects ◽  
Resonance Modes ◽  
Combined Motion ◽  
Near Resonance ◽  
Liquid Behavior ◽  
Steady Mode ◽  
The Mean ◽  
Spherical Reservoir

Within the framework of combined motion the effect of ratio of masses of reservoir and liquid on the behavior of a free surface of liquid in the reservoir of spherical shape is studied. We suppose that liquid is ideal and it fills partially the reservoir. Mathematical modelling is done on the basis of the model, which takes into account combined character of nonlinear dynamics of liquid and the reservoir. Examples were done based on mathematical model of combined motion of liquid in spherical reservoir and free-surfaced liquid under harmonic force disturbance in horizontal direction. Two cases of the ratio of masses in the system are considered. First, the mass of the reservoir is 5 times less than the mass of the liquid; the mass of the reservoir is 5 times greater than the mass of the liquid. In order to identify specific features of the system behavior, the results were compared with the results for liquid behavior in cylindrical and conical reservoirs. It was ascertained that mass increasing has no tendency of converging to a steady mode of motion, which was confirmed experimentally. Distinctions of manifestation of nonlinear processes for the below-resonance, near-resonance and above-resonance modes are shown. We note manifestation of nonlinear effects such as modulation, the presence of high-frequency normal modes of oscillations, antiresonance and drift of the mean of oscillations.

scholarly journals Correcting the Error in Measuring Radiation Received by a Person: Introducing Cylindrical Radiometers

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5085 ◽  
Author(s):  
Brown
Keyword(s):  
Vertical Cylinder ◽  
Spherical Shape ◽  
Indoor Environments ◽  
New Instrument ◽  
Human Energy ◽  
Integral Radiation ◽  
Outdoor Environments ◽  
The Mean ◽  
Radiant Temperature ◽  
New Instruments

Most human energy budget models consider a person to be approximately cylindrical in shape when estimating or measuring the amount of radiation that they receive in a given environment. Yet, the most commonly used instrument for measuring the amount of radiation received by a person is the globe thermometer. The spherical shape of this instrument was designed to be used indoors where radiation is received approximately equally from all directions. But in outdoor environments, radiation can be strongly directional, making the sphere an inappropriate shape. The international standard for measuring radiation received by a person, the Integral Radiation Measurement (IRM) method, yields a measure of the Mean Radiant Temperature (Tmrt). This method uses radiometers oriented in the four cardinal directions, plus up and down. However, this setup essentially estimates the amount of energy received by a square peg, not a cylinder. This paper identifies the errors introduced by both the sphere and the peg, and introduces a set of two new instrument that can be used to directly measure the amount of radiation received by a vertical cylinder in outdoor environments. The Cylindrical Pyranometer measures the amount of solar radiation received by a vertical cylinder, and the Cylindrical Pyrgeometer measures the amount of terrestrial radiation received. While the globe thermometer is still valid for use in indoor environments, these two new instruments should become the standard for measuring radiation received by people in outdoor environments.

scholarly journals Nonlinear gas oscillations in pipes. Part 1. Theory

1973 ◽  
Vol 59 (1) ◽  
pp. 23-46 ◽  
Author(s):  
J. Jimenez
Keyword(s):  
Boundary Conditions ◽  
Equations Of Motion ◽  
Nonlinear Effects ◽  
Wave Form ◽  
Cube Root ◽  
Acoustic Oscillations ◽  
Open Mouth ◽  
Near Resonance ◽  
Reflexion Coefficient ◽  
Two Parameters

The problem of forced acoustic oscillations in a pipe is studied theoretically. The oscillations are produced by a moving piston in one end of the pipe, while a variety of boundary conditions ranging from a completely closed to a completely open mouth at the other end are considered. All these boundary conditions are modelled by two parameters: a length correction and a reflexion coefficient equivalent to the acoustic impedance.The linear theory predicts large amplitudes near resonance and nonlinear effects become crucially important. By expanding the equations of motion in a series in the Mach number, both the amplitude and wave form of the oscillation are predicted there.In both the open- and closed-end cases the need for shock waves in some range of parameters is found. The amplitude of the oscillation is different for the two cases, however, being proportional to the square root of the piston amplitude in the closed-end case and to the cube root for the open end.

Two Methods to Broaden the Bandwidth of a Nonlinear Piezoelectric Bimorph Power Harvester

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Hongping Hu ◽  
Longxiang Dai ◽  
Hao Chen ◽  
Shan Jiang ◽  
Hairen Wang ◽  
...  
Keyword(s):  
Large Deformations ◽  
Initial Conditions ◽  
Flexural Vibration ◽  
Nonlinear Effects ◽  
Voltage Source ◽  
Energy Scavenging ◽  
Piezoelectric Bimorph ◽  
Near Resonance ◽  
Jump Phenomena ◽  
Power Harvester

We propose two methods to broaden the operation bandwidth of a nonlinear pinned–pinned piezoelectric bimorph power harvester. The energy-scavenging structure consists of a properly poled and electroded flexible bimorph with a metallic layer in the middle, and is subjected to flexural vibration. Nonlinear effects at large deformations near resonance are considered by taking the in-plane extension of the bimorph into account. The resulting output powers are multivalued and exhibit jump phenomena. Two methods to broaden the operation bandwidth are proposed: The first method is to extend the operation frequency to the left single-valued region through optimal design. The second method is to excite optimal initial conditions with a voltage source. Larger output powers in the multivalued region of the nonlinear harvester are obtained. Hence, the operation bandwidth is broadened from the left single-valued region to the whole multivalued region.

Nonlinear Adaptive Vibration Absorber for the Control of Plate Vibrations

2001 ◽  
Author(s):  
Osama N. Ashour ◽  
Ali H. Nayfeh
Keyword(s):  
Control Strategy ◽  
Flexible Structures ◽  
Digital Signal ◽  
Nonlinear Effects ◽  
Frequency Measurement ◽  
Control Technique ◽  
Vibration Absorber ◽  
Plate Vibrations ◽  
Near Resonance ◽  
Modeling Software

Abstract A nonlinear adaptive vibration absorber to control the vibrations of flexible structures is investigated. The absorber is based on the saturation phenomenon associated with dynamical systems possessing quadratic nonlinearities and a two-to-one internal resonance. The technique is implemented by coupling a second-order controller with the structure’s response through a sensor and an actuator. Energy is exchanged between the structure and the controller and, near resonance, the structure’s response saturates to a small value. Experimental results are presented for the control of a rectangular plate and a cantilever beam using piezoelectric ceramics and magnetostrictive alloys as actuators. The control technique is implemented using a digital signal processing board and a modeling software. The control strategy is made adaptive by incorporating an efficient frequency-measurement technique. This is validated by successfully testing the control strategy for a non-conventional problem, where nonlinear effects hinder the application of the nonadaptive controller.

Influence of Electrical Parameter on the Size of Superalloy Powders Prepared by Spark Plasma Discharge Process

2007 ◽  
Vol 561-565 ◽  
pp. 403-406
Author(s):  
Jun Yu ◽  
Chang Chun Ge ◽  
Guo Hua Ni ◽  
Lu Lu Meng ◽  
Wei Ping Shen ◽  
...  
Keyword(s):  
Particle Size ◽  
Pulse Duration ◽  
Electrical Parameter ◽  
Spherical Shape ◽  
Plasma Discharge ◽  
Discharge Process ◽  
Small Particle Size ◽  
Spark Plasma ◽  
Mean Size ◽  
The Mean

Superalloy powders, which have a small particle size and spherical shape, were prepared by a spark plasma discharge process. The electrical parameter, spark voltage, current and pulse duration have very important effects on the size distribution of produced superalloy powders. When current or pulse duration changed the mean size significantly changed.

Thermal effect in the resonance fluorescence of a two-level system

1991 ◽  
Vol 69 (11) ◽  
pp. 1367-1372
Author(s):  
C. H. A. Fonseca ◽  
L. A. Amarante Ribeiro
Keyword(s):  
Equations Of Motion ◽  
Normal Modes ◽  
Thermal Fluctuations ◽  
Harmonic Oscillators ◽  
Thermal Bath ◽  
Resonance Fluorescence ◽  
Level System ◽  
Near Resonance ◽  
Intensity Correlation Function ◽  
Heisenberg Equations

The damped two-level system, driven by a strong incident classical field near resonance frequency is subjected to the effect of thermal fluctuations. To simulate the thermal bath we introduce a large system of harmonic oscillators that represents the normal modes of the thermal radiation field. From the Heisenberg equations of motion we calculate the power spectrum of the scattered field and the intensity correlation function. The results show that the presence of the bath dramatically modifies the light scattered by the two-level system when compared with the case without a thermal bath.

A Method of Calculating Space Free Resonance Modes of an Aircraft

1953 ◽  
Vol 57 (510) ◽  
pp. 420-422 ◽  
Author(s):  
B. A. Hunn
Keyword(s):  
Free Space ◽  
Degrees Of Freedom ◽  
Normal Modes ◽  
Characteristic Root ◽  
Frequency Range ◽  
Resonance Modes ◽  
Characteristic Roots ◽  
Modes Of Vibration ◽  
4 Degrees Of Freedom

The problem of deducing resonance modes of vibration of an aircraft in free space is a concomitant of flutter calculations if the number of degrees of freedom used is to be small. When the structure is complex in that it involves wings, fuselage and tailplane, each of which possesses infinitely many normal modes, it becomes apparent that the number of point masses which must be considered, in constructing a dynamical equivalent to give a sufficient coverage of the frequency range in which flutter is likely, is very large. For example, it may be necessary to use four rods per wing and per tailplane and four point masses on the fuselage. This would involve 8 + 8 + 4 degrees of freedom, and if the usual technique of characteristic roots is used it would be necessary to consider a characteristic root matrix of order 20 × 20.

Nonlinear thermal convection in an elasticoviscous layer heated from below

1977 ◽  
Vol 356 (1685) ◽  
pp. 161-176 ◽  
Keyword(s):  
Linear Theory ◽  
Nonlinear Effects ◽  
Horizontal Layer ◽  
Plane Poiseuille Flow ◽  
Elastic Parameters ◽  
Temperature Contrast ◽  
The Mean ◽  
Exchange Of Stability ◽  
Steady Convection ◽  
Adiabatic Temperature Gradient

The linear and nonlinear stabilities of a horizontal layer of an elasticoviscous fluid, whose stress-rate-of-strain relations are due to Oldroyd (1958), are studied. In the linear theory it is already shown that steady convection (the situation generally referred to as the exchange of stability) is preferred for all relevant values of the Prandtl number (which is the ratio of the kinematic viscosity to the thermal diffusivity). The study of nonlinear effects for slightly supercritical Rayleigh number (which measures the temperature contrast across the layer) shows that plane disturbances for the case where the exchange of stability is valid and plane or centred disturbances for the case of overstability are governed by equations similar to those derived by Hocking, Stewartson & Stuart (1972) for plane Poiseuille flow. The influence of elasticity is to give rise to a burst only when the principle of exchange of stability is valid and provided certain conditions relating to the elastic parameters of the fluid are satisfied. The effect of the adiabatic temperature gradient is also discussed. It is shown that it stabilizes the layer in the linear theory. However, in the nonlinear theory it can destabilize the layer if the ratio the mean temperature of the layer to the temperature difference across the layer is large enough. For most practical purposes it does not influence the conditions necessary for a burst to occur.

scholarly journals The thermal emission of Centaurs and trans-Neptunian objects at millimeter wavelengths from ALMA observations

2017 ◽  
Vol 608 ◽  
pp. A45 ◽  
Author(s):  
E. Lellouch ◽  
R. Moreno ◽  
T. Müller ◽  
S. Fornasier ◽  
P. Santos-Sanz ◽  
...  
Keyword(s):  
Thermal Emission ◽  
Spherical Shape ◽  
Far Infrared ◽  
Physical Parameters ◽  
A Value ◽  
Thermal Measurements ◽  
Solar System Bodies ◽  
Flux Measurements ◽  
The Mean ◽  
Pole Orientation

The sensitivity of ALMA makes it possible to detect thermal mm/submm emission from small and/or distant solar system bodies at the sub-mJy level. While the measured fluxes are primarily sensitive to the objects’ diameters, deriving precise sizes is somewhat hampered by the uncertain effective emissivity at these wavelengths. Following recent work presenting ALMA data for four trans-Neptunian objects (TNOs) with satellites, we report on ALMA 233 GHz (1.29 mm) flux measurements of four Centaurs (2002 GZ32, Bienor, Chiron, Chariklo) and two other TNOs (Huya and Makemake), sampling a range of sizes, albedos, and compositions. These thermal fluxes are combined with previously published fluxes in the mid/far infrared in order to derive their relative emissivity at radio (mm/submm) wavelengths, using the Near Earth Asteroid Standard Model (NEATM) and thermophysical models. We reassess earlier thermal measurements of these and other objects – including Pluto/Charon and Varuna – exploring, in particular, effects due to non-spherical shape and varying apparent pole orientation whenever information is available, and show that these effects can be key for reconciling previous diameter determinations and correctly estimating the spectral emissivities. We also evaluate the possible contribution to thermal fluxes of established (Chariklo) or claimed (Chiron) ring systems. For Chariklo, the rings do not impact the diameter determinations by more than ~5%; for Chiron, invoking a ring system does not help in improving the consistency between the numerous past size measurements. As a general conclusion, all the objects, except Makemake, have radio emissivities significantly lower than unity. Although the emissivity values show diversity, we do not find any significant trend with physical parameters such as diameter, composition, beaming factor, albedo, or color, but we suggest that the emissivity could be correlated with grain size. The mean relative radio emissivity is found to be 0.70 ± 0.13, a value that we recommend for the analysis of further mm/submm data.

scholarly journals Error growth and dynamical vectors during southern hemisphere blocking

2004 ◽  
Vol 11 (1) ◽  
pp. 99-118 ◽  
Author(s):  
M. Wei ◽  
J. S. Frederiksen
Keyword(s):  
Southern Hemisphere ◽  
Normal Modes ◽  
Time Interval ◽  
Random Perturbations ◽  
Time Intervals ◽  
Amplification Factors ◽  
Fast Growing ◽  
A Value ◽  
The Mean ◽  
Basic States

Abstract. The structural organization of initially random perturbations or "errors" evolving in a barotropic tangent linear model with time-dependent basic states taken from observations, is examined for cases of block development, maturation and decay in the Southern Hemisphere atmosphere during April, November and December 1989. We determine statistical results relating the structures of evolved errors to singular vectors (SVs), Lyapunov vectors (LVs) and finite-time normal modes (FTNMs). The statistics of 100 evolved error fields are studied for six day periods or longer and compared with the growth and structures of leading fast growing SVs, LVs and FTNMs. The SVs are studied in the kinetic energy (KE), enstrophy (EN) and streamfunction (SF) norms, while all FTNMs and the first LV are norm independent. The mean of the largest pattern correlations between the 100 error fields and dynamical vectors, taken over the five fastest growing SVs, in any of the three norms, or over the five fastest growing FTNMs, increases with increasing time interval to a value close to 0.6 after six days. Corresponding pattern correlations with the five fastest growing LVs are slightly lower. The leading dynamical vectors (SVs 1, FTNM1 or LV 1) generally, but not always, give the largest pattern correlations with the error fields. It is found that viscosity slightly increases the average correlations between the evolved errors and LV 1 and evolved SVs 1. Mean pattern correlations with fast growing dynamical vectors increase further for time intervals longer than six days. The properties of the dynamical vectors during Southern Hemisphere blocking are briefly outlined. After a few days integration, the structures of the leading evolved SVs in the KE, EN and SF norms, are in general quite similar and also similar to some of the dominant FTNMs that are norm independent. For optimization times of six days or less, the evolved SVs and FTNMs are, in general, different from the dominant LVs on the same day. Nevertheless, amplification factors of the first FTNMs and first LVs are very similar, and also similar to, but slightly larger than, the mean amplification factor of 100 initially random perturbations in the SF norm, while the amplification factors in the SF norm of KE SVs 1 and SF SV 1 are much higher. For longer optimization times, the first SVs and the first FTNM increasingly turn towards the leading LV with convergence achieved within a month.

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