Rotational Moment Of Inertia Research Articles

Electro-Hydrostatic Actuator의 성능해석

정유압 방식 EHA는 종래의 밸브 제어 방식 전기유압 구동장치와 전혀 다른 특성을 나타낸다. 본 논문에서는 EHA의 비선형 요소를 포함한 수학적 모델을 유도하고 실험적으로 검증하였다. 이 수학적 모델을 근거로 전기 모터로 구동되는 유압 펌프, 파이프 배관 그리고 유압 실린더로 구성되는 EHA의 시물레이션 모델을 개발하여 주요 설계 인자인 모터 토크의 피크치, 펌프의 관성 모멘트 등이 제어 성능에 미치는 영향을 분석하였다. 여기에서 실험 조건은 의도적으로 과도기에서 모터 토크가 포화되도록 선정하였다. 그 결과로서 최대 속도로 동작하는 EHA의 제어 정밀도를 개선하기 위한 설계 조건을 조사하였다. The EHA(Electro-hydrostatic Actuator) reveals completely different characteristics from the conventional valve-controlled Electro-hydraulic actuators. In this paper, its mathematical model including nonlinear elements was derived to be verified by experiments. Based on this, a simulation program was developed for the EHAs consisting of an electric motor driven hydraulic pump, pipe lines and a cylinder. The influence of important design parameters such as peak motor torque and rotational inertia moment of the hydraulic pump on control performance was investigated, where the test condition was intentionally selected so that the motor torque was saturated during the transient phase. As a result, design requirements for improving the control accuracy under full speed operation conditions of the EHAs were investigated.

Bose-Einstein condensation: Where many become one and, therefore, there is plenty of room at the bottom

Bose{Einstein condensation and super∞uidity are well known to occur in the dilute gaseous as well as in the dense liquid state of matter having a flxed number of Bose particles. Very recently, experimental evidence has been obtained for the probable realization of BEC and super∞uidity in 4 He in the solid state too, as revealed through its non-classical rotational moment of inertia { smaller than that for the solid. Such a solid that can also subtend a ∞ow as super∞uid { and hence a supersolid { is indeed a surprise of condensed matter physics. In this conversation, an order-parameter description for the supersolid state will be given in which the super∞uid ∞ow is decoupled from the crystalline density modulation which remains at rest in the laboratory frame, thus giving it a non- classical inertia.

Finite element analysis and optimization of composite wheelchair wheels

A methodology for the design of Paralympics wheelchair wheels has been developed and provided a framework for comparison between design solutions. Finite element analysis was used as a tool to develop an understanding of wheel design, provide a basis for evaluation of design solutions, and as a mean of design optimisation. A finite element model of an existing wheel design was created and analysed. It was found that the pushrim was significantly over designed for the application. As such, wheel improvement focused on redesign of this component. A number of design solutions were analysed and compared based on weight, rotational moment of inertia, side profile surface area, and wheel stiffness. From this, it was decided that a thin pushrim attached via spokes to the rim and the hub in a tangential spoking pattern would offer the best solution.

Observation of Non-Classical Rotational Inertia in Solid 4He Confined in Porous Gold

Recent torsional oscillator measurements on solid 4He confined in Vycor glass at 62 bars show supersolid response, an abrupt drop in rotational moment of inertia, at 175 mK1. We have investigated the pore-size dependence of the supersolid behavior by confining solid 4He in a different porous host, porous gold, of a considerably larger pore diameter. When solid 4He in porous gold is cooled below 0.2 K a sharp drop in the resonant period is found. The supersolid response exhibits a strong dependence on the amplitude of oscillation.

High-resolution infrared spectra of carbonyl sulfide solvated with helium atoms

Infrared spectra of HeN–OCS clusters with N up to about 20 have been studied in the 2062 cm−1 region of the O–C stretching vibration using a tunable diode laser spectrometer to probe pulsed supersonic expansions from moderately high-pressure (<35 atm) cooled (>−60 °C) jet sources. Resolved rotation-vibration transitions have been assigned for the clusters with N=2–8, and these assignments have been confirmed in detail by observations of the corresponding pure rotational transitions in the microwave region. The vibrational frequencies (band origins) were observed to move to higher frequencies (blueshift) for N=2–5, continuing the shift previously observed for the binary complex, He–OCS. Then, for N=6–8, the vibrational frequency moves back in the direction of lower frequencies (redshift), leading towards the limiting redshift previously observed in larger helium nanodroplets with N≈103–104. These vibrational shifts are consistent with a model in which the first five helium atoms fill a “ring” around the “equator” of the OCS molecule, with the subsequent heliums then taking positions closer to the ends. The cluster rotational constants decrease monotonically (increasing rotational moments of inertia) for N=1–8, falling below the value previously observed for the “free” rotation of OCS in helium nanodroplets. Strong, sharp spectral lines from clusters in the size range N≈9–20 were also observed, but not assigned. This difficulty in extending the analysis for N>8 may be related to the onset of partially free internal rotation of the OCS within the helium cluster, which in turn has interesting implications for the nature of superfluid-type behavior in this finite scale system.

An experimental study for drivability improvements in vehicle acceleration mode

Modern vehicles require a high degree of refinement, including good drivability. Vehicle drivability, which becomes a key decisive factor for marketability, is affected by many parameters such as engine control and the dynamic characteristics in the drivelines. Therefore, engine and drivetrain characteristics should be analysed to achieve a well-balanced vehicle response simultaneously. This paper describes experimental procedures that have been developed to measure engine torque and investigate shuffle characteristics. A simplified powertrain model is presented for vehicle dynamic response analysis. Submodels within the model are the engine and drivetrain. Using this model, the friction and inertial moment for each submodel were measured, and effects of parameters were analysed. To analyse vehicle dynamics behaviour, frictional torques and the rotational inertia moment of the engine and the drivetrain were measured. Shuffle characteristics at the tip-in condition were investigated in an experimental vehicle at the second and third gear stages. It was found that shuffle characteristics are caused by sudden changes in engine torque and have a different vibration frequency with gear stage variation. The rotational inertia moment of the engine, including flywheel rotation, is a key factor influencing the shuffle characteristics.

SU(3) monopoles and their fields

Some aspects of the fields of charge two SU(3) monopoles with minimal symmetry breaking are discussed. A certain class of solutions look like SU(2) monopoles embedded in SU(3) with a transition region or ``cloud'' surrounding the monopoles. For large cloud size the relative moduli space metric splits as a direct product AH\times R^4 where AH is the Atiyah-Hitchin metric for SU(2) monopoles and R^4 has the flat metric. Thus the cloud is parametrised by R^4 which corresponds to its radius and SO(3) orientation. We solve for the long-range fields in this region, and examine the energy density and rotational moments of inertia. The moduli space metric for these monopoles, given by Dancer, is also expressed in a more explicit form.

A new procedure to determine external power output during handrim wheelchair propulsion on a roller ergometer: a reliability study.

This study presents a mathematical model by which power output (PO) delivered to the rear wheel during handrim wheelchair propulsion on a roller ergometer can be determined for individual wheelchair-user combinations. PO is calculated from the torque applied to the wheel and its angular velocity. The torque applied is a function of one total internal torque of the wheelchair-ergometer system, the rotational moment of inertia of the rear wheel, the one of the roller and its angular acceleration. The total internal torque reflects all internal friction forces and is determined with a deceleration test. To assess the reliability of this approach, 11 able-bodied subjects underwent progressively increasing exercise tests on two different occasions. PO values ranged from 12 to 63 W and were highly reliable (r2 > 0.95). Peak physiological responses were never different from test 1 and 2 (repeated measures ANOVA; p: N.S.) and correlations were 0.90, 0.72, 0.88, 0.82, 0.70 and 0.85 for PO, oxygen uptake (VO2), heart rate, minute ventilation, carbon dioxide production and blood lactate concentration, respectively. After an initial increase, gross mechanical efficiency dropped at higher velocities, with values ranging from 4.64 to 11.26%. In conclusion, the roller ergometer, the mathematical model to determine PO and the protocol used seem to be adequate to exercise test people in a handrim wheelchair. It is feasible to apply the theoretical procedure to other roller ergometers which would allow for comparisons of exercise intensities and protocols between different devices used in exercise physiology and rehabilitation.

Nuclear Collective Dynamics of Shape Phase Transition. I

The quasi-bands structure for the transition from spherical to deformed shape in Sm isotopes is studied by making use of the self-consistent collective coordinate method. The five-quadrupole collective coordinates and momenta are explicitly treated and they are canonically transformed into the intrinsic shape and rotational degrees of freedom with respect to the body-fixed reference frame. From the analysis of the collective kinetic energy in the intrinsic system, the higher-order anharmonic terms including the coupling with two-quasi-particle non-collective states play an essential role in the description of the mass parameters and rotational moments of inertia.

Nuclear Collective Dynamics of Shape Phase Transition. I: Quasi-Bands Structure and Intrinsic Quadrupole Motions

The quasi-bands structure for the transition from spherical to deformed shape in Sm isotopes is studied by making use of the self-consistent collective coordinate method. The five-quadrupole collective coordinates and momenta are explicitly treated and they are canonically transformed into the intrinsic shape and rotational degrees of freedom with respect to the body-fixed reference frame. From the analysis of the collective kinetic energy in the intrinsic system, the higher-order anharmonic terms including the coupling with two-quasi-particle non-collective states play an essential role in the description of the mass parameters and rotational moments of inertia.

Effect of rotation on molecular shape

The moment of inertia of CH3NC about the z axis is very small, and the rotational spacings for increasing quantum number K are large. In the T-shaped transition state for isomerization to CH3CN, on the other hand, both the N and C atoms lie off the axis, and the moment of inertia for rotation in this direction becomes large; thus, for a given amount of angular momentum, the energies of the stable molecules are raised very much more than the energy of the transition state. In the limit of very high K, triangular C-N-C configurations become the most stable, and the two linear arrangements become transition states. As a result, the equilibrium arrangements of the heavy atoms in CH3NC and, to a lesser extent in CH3CN, become nonlinear at quite moderate rotational energies, and the possibility of detecting this distortion experimentally is discussed.

Quantization of the Nambu-Jona-Lasinio soliton and the nucleon-delta splitting

The self-consistent chiral soliton of the Nambu-Jona-Lasinio model is quantized by means of the collective coordinate method and the rotational moment of inertia is evaluated. For constituent masses around 400 MeV the nucleon-delta splitting agrees well with the experimental data. The contribution of the sea quarks to the moment of inertia is about 20%. In this region the isoscalar quadratic radius of the nucleon is reproduced as well and a clear valence quark picture prevails.

Nuclear structure of light thallium isotopes as deduced from laser spectroscopy on a fast atom beam.

The neutron-deficient isotopes /sup 189-194/Tl have been studied using collinear fast atom beam laser spectroscopy with mass-separated beams of 7 x 10/sup 4/ to 4 x 10/sup 5/ atoms per second. By laser excitation of the 535 nm atomic transitions of atoms in the beam, the 6s/sup 2/7s /sup 2/S/sub 1/2/ and 6s/sup 2/6p /sup 2/P/sub 3/2/ hyperfine structures were measured, as were the isotope shifts of the 535 nm transitions. From these, the magnetic dipole moments, spectroscopic quadrupole moments, and isotopic changes in mean-square charge radii were deduced. A large isomer shift in /sup 193/Tl was observed, implying a larger deformation in the (9/2/sup -/ isomer than in the (1/2/sup +/ ground state. The /sup 189,191,193/Tl/sup m/ isotopes have deformations that increase as the mass decreases. A deformed shell model calculation indicates that this increase in deformation can account for the drop in energy of the (9/2/sup -/ bandhead in these isotopes. An increase in neutron pairing correlations, having opposite and compensating effects on the rotational moment of inertia, maintains the spacing of the levels in the (9/2/sup -/ strong-coupled band. Results for /sup 194/Tl/sup m/ differ from previously published values, but are consistent with the /sup 190,192/Tl/sup m/more » data.« less

The born-oppenheimer theory of nuclear rotations and vibrations

In this paper it is demonstrated that there is a fruitful analogy between nuclear and molecular collective rotations and vibrations. In order to implement this analogy, and to construct the analog of the factorable molecular Born-Oppenheimer trial function, one must transform into a representa- tion, in which the nuclear collective “position” operators and the residual intrinsic operators are diagonal. In this representation, the trial function is assumed factorable. Using projection operator techniques, this trial function can be transformed back into a particle coordinate representation, so that conventional many-body techniques can be used. The collective operators are “chosen” only to the extent needed to identify the “type” of collective process that one intends to describe, by stating their transformation properties under the standard symmetry operations in coordinate-, spin- and isospin space: In the present case, the collective operators form a symmetric, second rank tensor, are isoscalar, and thus describe rotations, and size and quadrupole shape oscillations. A more detailed determination of these operators is based on the dynamical argument of minimal coupling between collective and intrinsic modes of excitation. One then finds that in the harmonic limit, vibrations have frequencies given by RPA type equations, and rotational moments of inertia are determined by self-consistent cranking type prescriptions.

Frequency-Response Matching to Optimize Wind-Turbine Test Data Correlation

Pre-averaging is often applied to wind turbine test data to improve correlation between wind speed and power output data. In the past, trial and error or intuition have been used in the selection of pre-averaging time and researchers and institutions have differed widely in their pre-averaging practice. In this paper a standardized method is proposed for selection of the optimum pre-averaging time. The method selects an averaging time such that the test data are low-pass-filtered at the same frequency as the response frequency of the test wind turbine/anemometer system. A theoretial method is provided for estimation of the wind system transfer function as a function of the anemometer location, rotor moment of inertia, the stiffness of the connection between the rotor and the electrical grid, hub height, rotor speed and wind speed. The method is based in proven theory, repeatable, easy to use and applicable to a wide range of wind turbines and test conditions. Results of the transfer function predictions are compared with the measured response of two wind systems. Agreement between the predicted and measured response is completely adequate for the purposes of the method. Example results of calculated averaging times are presented for several wind turbines. In addition, a case study is used to demonstrate the dramatic effects of test design and data analysis methods on the results of a power coefficient measurement.

Macroscopic model of rotating nuclei.

I present a macroscopic model for the energy of rotating nuclei which has several refinements relative to the rotating-liquid-drop model. Of most importance are the inclusion of finite-range effects in the nuclear surface energy by means of a Yukawa-plus-exponential potential, finite surface diffuseness effects in the Coulomb energy and in the rotational moments of inertia, and an improved specification of nuclear shapes. With this model I calculate the properties of points of equilibrium corresponding to nuclear ground states and fission saddle points. The results are qualitatively similar to those of the rotating-liquid-drop model, but there are significant quantitative differences in fission-barrier heights and moments of inertia. Fission barriers for nonrotating nuclei are calculated for nuclei with atomic numbers varying from 14 to 117. For rotating nuclei, detailed results are given for the entire range of angular momentum for which a fission barrier exists, for nuclei with atomic numbers from 20 to 100, and for mass numbers which exceed the range of known nuclei. The calculated barriers are lower than liquid-drop-model barriers for lighter nuclei and are consistent with those deduced from experimental fission-fusion data over a wide range of nuclear species. The present calculations indicate that super-deformed rotating ground states, which are predicted in the liquid-drop model, would not survive fission long enough to undergo electromagnetic decay. Multiparameter functions which approximately reproduce the calculated results for barrier heights and moments of inertia are described.

Neutron chopper phasing for a quasi-periodic pulsed neutron source

A control system has been developed which phases a neutron chopper to a pulsed neutron source which has a randomly varying pulse repetition rate. The chopper is driven by an induction motor and stabilized by a high precision proportional derivative (PD) feedback circuit. A control theory is developed which relates the system response bandwidth to motor and driver characteristics and rotor moment of inertia. Experiments with choppers operating in a phase-locked loop with the Los Alamos pulsed neutron source, the WNR/PSR Facility, show that (1) the control system can hold the phase of the chopper within the band in which the pulsed source will accept trigger pulses; and (2) when the chopper is used to trigger the pulsed source within this hand, the phase between source and chopper can be controlled to less than 1 μs.

Quantized ATDHF calculations for the α + 16O 20Ne system

The quantized adiabatic time-dependent Hartree-Fock theory (quantized ATDHF.) is numerically applied to the α + 16O 20Ne system. Density-dependent interactions with finite-range direct Yukawa-tenns are used and the single-particle wave functions are represented on a three-dimensional grid in coordinate and momentum space. It is demonstrated that the evaluation of observables is independent on the actual choice of the collective coordinate. For the 20Ne ground state the importance of parity projection is shown. For the description of the dynamics of the α + 16O 20Ne system the collective potential, the mass parameter, rotational moments of inertia and quantum corrections (zero point energies) are evaluated microscopically. The collective Schrödinger equation is then solved for the ground-state rotational band and for the α- 16O elastic scattering. In both cases good agreement with experimental data is obtained.

A self-consistent description of systems with many interacting bosons

A self-consistent description for the ground state of many interacting bosons is discussed. The excited bandheads are obtained by solving the TDA and RPA equations. The latter can be used to isolate the spurious states that arise as a consequence of broken symmetries. The rotational moment of inertia is obtained in different approximations. The interband and intraband electromagnetic decay modes are also analyzed. The use of this framework is exemplified describing systems containing bosons with angular momenta l = 0, 2 and 4.

Quantized ATDHF calculations for subbarrier fusion of heavy ions

The quantized adiabatic time-dependent Hartree-Fock theory (quantized ATDHF) is applied to the subbarrier fusion process of 16 O + 16 O → 32 S . The corresponding optimal, i.e. maximally decoupled collective path is evaluated by means of three-dimensional coordinate and momentum space grid techniques using the Bonche-Koonin-Negele interaction completed by the Coulomb force. Collective mass parameters, potentials, quantum corrections and rotational moments of inertia are evaluated in dependence of the distance between the ions. The results are compared to experimental fusion data and to the outcome of Hartree-Fock with quadrupole constraint.