Large Moment Of Inertia Research Articles

Coupled Attitude-Orbit Control of Flexible Solar Sail for Displaced Solar Orbit

The solar sail is a new type of spacecraft for deep space exploration that is propelled by solar radiation pressure. The solar sail is large, has a large moment of inertia, and is highly flexible, and its motion involves a coupling of the orbit, the attitude, and structural vibration. With the coupling effect of the orbit and the attitude included, a non-Keplarian displaced solar orbit is designed. In the rotating frame, the solar sail has a stable equilibrium point, and an attitude controller is employed for coupled attitude-orbit control. With control, the time required for eliminating the orbital deflection is much larger than that required for the attitude deflection. Including the additional influence of the flexibility of the solar sail, the structure shows a sustained, high-frequency vibration, which also leads to sustained and high-frequency likewise small vibrations of the orbit and attitude. This work demonstrates the importance of including the structural flexibility into the coupling effect of the solar sail for long-term missions in space.

평균대 제자리 무릎 구부려 뒤공중돌기 기술의 운동역학적 분석

This study was to perform the kinetic analysis of tucked backward salto on the balance beam. Eight women's gymnastics players(age: <TEX>$15.88{\pm}2.45yrs$</TEX>, career: <TEX>$6.38{\pm}0.52yrs$</TEX>, height: <TEX>$152.38{\pm}7.35cm$</TEX>, weight: <TEX>$44.25{\pm}7.54kg$</TEX>) of the I-region participated in this study. The kinematic variables were analyzed response time of motion, angle, velocity, acceleration and the kinetic variables were analyzed ground reaction force(GRF) of motion. For measure and analysis of kinematic and kinetic variables of this study, used to synchronized to 6 Eagle camera and 1 force plate, used to the Cortex(Ver. 1.0) for analyzed of variables. The results were as follows; To the kinematic variables of tucked backward salto on the balance beam, a time appeared longer landing than air rotation, changes of angle regulated segment of body smaller moment of inertia when air rotation, larger moment of inertia when releasing and landing. A velocity appeared fast motion when releasing and air rotation of body, but appeared more decelerations from landing and acceleration showed to be tended to velocity. A GRF appears jump more than twice the weight at the moment that showed the power of motion to all subject.

Constraints on the Moment of Inertia of a Proto Neutron Star from the Hyperon Coupling Constants

The influence of the hyperon coupling constants on the moment of inertia of a proto neutron star has been investigated within the framework of relativistic mean field theory for the baryon octet {n,p,Λ,Σ − ,Σ0,Σ + ,Ξ − ,Ξ0} system. It is found that for a proto neutron star, the mass, the moment of inertia and their own maximum values as a function of radius R or M/R are all more sensitive to the hyperon coupling constants. For all the different hyperon coupling constants mentioned, the case of no hyperons corresponds to the largest moment of inertia.

Deletion of Cx43 from Osteocytes Results in Defective Bone Material Properties but Does Not Decrease Extrinsic Strength in Cortical Bone

Deletion of connexin (Cx) 43 from osteoblasts and osteocytes (OCN-Cre;Cx43(fl/-) mice) or from osteocytes only (DMP1-8kb-Cre;Cx43(fl/fl) mice) results in increased cortical, but not cancellous, osteocyte apoptosis and widening of the femoral midshaft without changes in cortical thickness. Despite the consequent larger moment of inertia, stiffness and ultimate load, measures of mechanical strength assessed by three-point bending, are not higher in either model of Cx43 deficiency due to reduced Young's modulus, a measure of the stiffness of the material per unit of area. In OCN-Cre;Cx43(fl/-) mice, this was accompanied by a reduced ratio of nonreducible/reducible collagen cross-links as assessed by Fourier transformed infrared imaging (FTIRI) in the femoral diaphysis. On the other hand, DMP1-8kb-Cre;Cx43(fl/fl) mice did not show a significant reduction in collagen maturation in the same skeletal site, but a small decrease in mineralization was detected by FTIRI. Remarkably, both osteoblastic and osteocytic cells lacking Cx43 expressed lower mRNA levels of lysyl oxidase, a crucial enzyme involved in collagen maturation. These findings suggest that Cx43 expression in osteoblasts is involved in maintaining the quality of the bone matrix in cortical bone through the maturation of collagen cross-links. Osteocytic Cx43 expression is important also to maintain the stiffness of the bone material, where Cx43 deficiency results in local reduction in mineralization, possibly due to osteocyte apoptosis.

Resonances in 28Si + 28Si. I: --Dinuclear Molecular Model with Axial Asymmetry--

A molecular model developed for resonances observed in medium light heavy-ion collisions is described. At high spins in 28Si+28Si (oblate-oblate system), a stable dinuclear configuration is found to be equator-equator touching one. The normal modes around the equilibrium are investigated. These modes are expected to be the origin of a large number of resonances observed. Furthermore, due to the axially asymmetric shape of the stable configuration of 28Si+28Si, the system rotates preferentially around the axis with the largest moment of inertia, which gives rise to wobbling motion ($K$-mixing). Energy spectra for the normal modes and for the extended model including the wobbling motion are given.

Linear Chain Structure of Four-αClusters inO16

We investigate the linear-chain configurations of four-$\alpha$ clusters in $^{16}$O using a Skyrme cranked Hartree-Fock method and discuss the relationship between the stability of such states and angular momentum. We show the existence of a region of angular momentum (13-18 $\hbar$) where the linear chain configuration is stabilized. For the first time we demonstrate that stable exotic states with a large moment of inertia ($\hbar^2/2\Theta$ $\sim$ 0.06-0.08 MeV) can exist.

CLUSTERING IN A = 10 NUCLEI

The experimental evidence for existence of cluster and molecular states in 10 Be , 10 B and 10 C is presented in details. For the most studied of the three, 10 Be , a rotational band have recently been firmly identified, with states having rather large moment of inertia. For the isobaric analogue states in 10 B first experimental results have been obtained and presented; some simple predictions for the 10 C nucleus are also given.

Shell model and band structures in 19O

We have studied the reaction ( ^7Li, p) on 13C targets at E lab = 44 MeV, populating states in the oxygen isotope 19O . The experiments were performed at the Tandem Laboratory (Maier-Leibniz Laboratorium) using the high-resolution Q3D magnetic spectrometer. States were populated up to an excitation energy of 21MeV, with an overall energy resolution of 45keV. We discuss shell model states and cluster bands related to the rotational bands in the 18O -isotope, using the weak-coupling approach. Similar to 18O , the broken intrinsic reflection symmetry in these states must give rise to rotational bands as parity doublets, so two K = 3/2 bands (parities, + and - are proposed with large moments of inertia. These are discussed in terms of an underlying cluster structure, ( ^14C ⊗ n ⊗ $ \alpha$ ) . An extended molecular binding diagram is proposed which includes the 14C -cluster.

Design of Frequency Control System for Centrifuge in Multi-Parameter Combined Environmental Testing Device

In the centrifuge of the multi-parameter combined environmental testing device, the three-phase induction motor could not be started directly at the frequency of 50Hz due to the large moment of inertia of the centrifuge rotor. Therefore, large torque output of the three-phase induction motor was required at low frequencies. And the specimen needed stepless rotational speed adjustment (40-130r/min). A set of frequency control system was developed based on vector control with PG, inverter and LabVIEW to solve these problems. The principle of the centrifuge was present. The principles of vector control with PG of three-phase induction motor were analyzed. Based on the mechanical characteristic of three-phase induction motor, vector control with PG was employed in the system. The system control software based on LabVIEW was presented, which realized stepless speed adjustment of the centrifuge on a computer. Experimental results show that the developed system could realize the stepless regulation of the specimen’s centrifugal acceleration.

Comparing the Performance of Optimally Tuned Dynamic Vibration Absorbers With Very Large or Very Small Moment of Inertia

In this article, the performance of a two degree-of-freedom dynamic vibration absorber (DVA) with very large or very small moment of inertia is studied. Although it has been shown previously that an optimally tuned DVA with a negligibly small moment of inertia marginally outperforms the optimally tuned DVA with a very large moment of inertia, the physical reasons for this have not been made clear. Using a simplified model of the stiffness elements of the DVA, it is shown that the two sets of parallel combinations of stiffness and damping elements of the DVA with negligibly small moments of inertia effectively act in series, rather than in parallel as in the other case. Furthermore, it is shown that the stiffness and damping elements can be represented as a single stiffness and a single damping element whose properties are frequency dependent. This frequency dependency means that there is additional freedom in choosing the optimum stiffness and damping of the DVA, which results in better performance.

Lyapunov instability of rough hard-disk fluids

The dynamical instability of rough hard-disk fluids in two dimensions is characterized through the Lyapunov spectrum and the Kolmogorov-Sinai entropy h{KS} for a wide range of densities and moments of inertia I . For small I the spectrum separates into translation-dominated and rotation-dominated parts. With increasing I the rotation-dominated part is gradually filled in at the expense of translation until such a separation becomes meaningless. At any density, the rate of phase-space mixing, given by h{KS} , becomes less and less effective the more the rotation affects the dynamics. However, the degree of dynamical chaos, measured by the maximum Lyapunov exponent, is only enhanced by the rotational degrees of freedom for high-density gases but is diminished for lower densities. Surprisingly, no traces of Lyapunov modes were found in the spectrum for larger moments of inertia. The spatial localization of the perturbation vector associated with the maximum exponent however persists for any I .

The effects of parameter variation on the gaits of passive walking models: simulations and experiments

SUMMARYWe have made a systematic study of the gait of a straight leg planar passive walking model through simulations and experiments. Three normalised parameters, which represent the foot radius, the position of the mass centre and the moment of inertia, are used to characterise the walking model.In the simulation, we have obtained the fixed points and the basins of attraction of the walking models with different parameter combinations by the aid of the cell mapping method. With the results of fixed points, we investigated the effects of parameter variations on the gait descriptors, including step length, period, average speed and energy inefficiency. A model that has a large basin of attraction has been obtained, and it can start walking far from its fixed point. However, the size of the basin of attraction is not a good measurement of robustness. Thus, we proposed floors with random slope angles or stairs with random heights to test robustness. Five hundred times of simulations with 100 non-dimensional time units were implemented for each parameter combination. The times that the walker failed to arrive at the end were recorded. The simulation results showed that the model with a larger foot radius and higher position of mass centre has a lower possibility of falling on uneven floors. A large moment of inertia is helpful for walking on a random slope angle floor, while low values of moment of inertia are good for navigating random stairs.Prototype experiments have validated the simulation results, which showed that models with larger feet have a longer step length and high speed. However, period differences were difficult to obtain in the experiments since the differences were very small. We have tested the sensitivity with the initial conditions of the models with different foot radii on a flat floor, and have also tested the robustness of the models on a floor with random slope angles. The times that the model reached the end of the floor were recorded. The experimental results showed that a large foot radius is good for improving the basin of attraction and robustness on uneven floors. Finally, the exceptions of the experiment are explained.

Detecting the crankshaft torsional vibration of diesel engines for combustion related diagnosis

Early fault detection and diagnosis for medium-speed diesel engines is important to ensure reliable operation throughout the course of their service. This work presents an investigation of the diesel engine combustion related fault detection capability of crankshaft torsional vibration. The encoder signal, often used for shaft speed measurement, has been used to construct the instantaneous angular speed (IAS) waveform, which actually represents the signature of the torsional vibration. Earlier studies have shown that the IAS signal and its fast Fourier transform (FFT) analysis are effective for monitoring engines with less than eight cylinders. The applicability to medium-speed engines, however, is strongly contested due to the high number of cylinders and large moment of inertia. Therefore the effectiveness of the FFT-based approach has further been enhanced by improving the signal processing to determine the IAS signal and subsequently tested on a 16-cylinder engine. In addition, a novel method of presentation, based on the polar coordinate system of the IAS signal, has also been introduced; to improve the discrimination features of the faults compared to the FFT-based approach of the IAS signal. The paper discusses two typical experimental studies on 16- and 20-cylinder engines, with and without faults, and the diagnosis results by the proposed polar presentation method. The results were also compared with the earlier FFT-based method of the IAS signal.

Angular Momentum Form of Verlet Algorithm for Rigid Molecules

A new simple algorithm is presented for solving the equations of motion for rigid molecules. These equations are integrated using a Verlet framework in the angular momentum form. This simple algorithm is named “the angular momentum Verlet algorithm”. For obtaining a high accuracy in molecular dynamics (MD) simulations, we introduce the scaling method with the constraint by Lagrange's method of undetermined multipliers. The results of MD simulations for carbon tetrachloride using the angular momentum Verlet algorithm are reported. The relative total energy fluctuations for carbon tetrachloride using the angular momentum Verlet algorithm are compared with those using the standard leap-frog and Gear predictor–corrector algorithms. The energy drift using the angular momentum Verlet algorithm is smaller than that using the leap-frog or Gear predictor–corrector algorithm, particularly for large time intervals. The MD simulations for A X n Y 4- n -type models having different moments of inertia are also carried out to investigate the effects of the angular momentum Verlet algorithm for molecules with different symmetries. We found that the time integrations for the model with the largest moment of inertia are stable. The scaling method with the constraint by Lagrange's method of undetermined multipliers in the angular momentum Verlet algorithm is effective in obtaining a smaller energy drift, particularly for large time intervals.

Hyperdeformed band in 36Ar populated in the 12C + 24Mg elastic scattering

The strongly oscillating angular distributions of the elastic scattering of 12C + 24Mg at energies around the Coulomb barrier (Ecm = 10.67 − 16.00 MeV) [1] were reproduced adding three Breit-Wigner resonance terms with J values of 6, 7 and 8 h respectively to the l = 6, 7 and 8 terms of the elastic S-matrix. The elastic scattering S-matrix was calculated using the double folding, deep, optical potential with non-local interaction, also called, Sao Paulo Potential [2]. All fifteen angular distributions could be well reproduced by the 3 resonances, located respectively at Ecm = 14.15, 15.8 and 16.9 MeV in the entrance channel, which correspond to excitation energies of 30.45, 32.1 and 33.2 MeV in the 36Ar compound nucleus. The J = 6, 7 and 8 h resonances fit well into a rotational molecular band, together with the J = 18, 20, 22 and 24 h resonances observed in the 16O + 20Ne elastic scattering [3]. The band head is at 29.5 MeV excitation energy in the 36Ar compound nucleus and has a large moment of inertia indicating a large deformation. Calculations of Rae and Merchant [4] propose the existence of a hyperdeformed band in 36Ar with 12C + 24Mg and 16O + 20Ne cluster structure.

A dynamic approximation of balanced gymnastics landings

A gymnast can balance after an uneven parallel bar dismount by contacting the ground with an appropriate body position and angular velocity. Balanceable gymnastics landings were predicted by dividing landing into two parts: a short duration impact phase when foot-mat contact forces are high, and a subsequent longer balancing phase during which the gymnast exerts active control at the joints to attenuate the resulting post-impact velocities and achieve a desired motionless terminal configuration. This paper identifies controllable sets of pre-impact landing positions and velocities for a typical female collegiate gymnast that are feasible targets for the end of flight following a single- and double-backward somersault uneven bar dismount with forward mass centre (CM) velocity. Simple algebraic impulse-momentum models for the impact phase determine impulses necessary to stop the feet and slow angular velocity. After impact, a dynamic analysis is needed to determine stability because non-negligible post-impact angular and linear velocities are possible. For almost all successfully balanced landings, ground contact occurs with the CM positioned above the feet and between the toe and heel, because the linear impact impulses that stop the feet also contribute to an angular impulse that slows angular momentum. Only at the largest pre-impact angular velocities following a double-somersault dismount can contact occur with the CM in front of the toe. The gymnast is in balanceable preimpact orientations longer when rotating more slowly and with a smaller angular momentum; therefore balance may be more likely after performing a single-somersault dismount with a large moment of inertia.

Rotational Dynamics of HCN−M (M = Na, K, Rb, Cs) van der Waals Complexes Formed on the Surface of Helium Nanodroplets

Infrared laser spectroscopy was used to probe the unique rotational dynamics of the HCN-M (M = Na, K, Rb, Cs) complexes formed on the surface of helium droplets. The nu1 CH stretch ro-vibrational spectra were measured revealing what appears to be the P and R contours of a nearly rigid linear rotor. To simulate the linear molecule spectra, given a rotational temperature of 0.37 K, effective moments of inertia, IB, were required to be 10(4)-10(5) amu.A2 larger than the ab initio predicted values. The large moments of inertia were found to be strongly dependent on both the mass of the complex and the size of the helium droplet, consistent with a model where the dopant is located in a dimple site on the surface of the droplet. In this model, the moment of inertia is representative of the rotational motion of the dopant on the surface about an inertial axis through the center of the droplet.

Collinear ternary cluster decay of hyperdeformed 60Zn at high angular momentum

Binary and ternary cluster decay of 60Zn compound nuclei at high angular momentum, formed in the 36Ar + 24Mg reaction at E lab(36Ar) = 195 MeV, has been measured in a unique kinematic coincidence setup consisting of two large area position sensitive (x, y) gas detector telescopes with Bragg-ionization chambers (BRS). The BRS provides the opportunity to measure the reaction angles in-and out-of-plane, and through Bragg-curve spectroscopy to achieve a complete identification of the nuclear charge for different final channels. We observed very narrow out-of-plane angular correlations for two heavy fragments emitted either in purely binary events or in events with a missing mass consisting of 2 and 3α particles. These narrow correlations are interpreted as ternary fission decay from compound nuclei at high angular momenta through an elongated (hyperdeformed) shape with a very large moment of inertia. In these stretched configurations, the lighter mass in the neck region remains at rest or with very low momentum in the center of mass.

Transfer, sequential decay, and quasi-free reactions induced by 18-MeV 6He beam on 6Li, 7Li, and 12C

The He-6 + Li-6,Li-7 and He-6 + C-12 scattering and reactions have been studied using an 18-MeV He-6 beam. Experimental results for the elastic scattering on all three targets are in fair agreement with optical model predictions, using the potentials found in the analysis of the Li-6 scattering on the same targets and at close beam energies. Several two-body exit channels show clear signatures of a direct reaction mechanism allowing extraction of spectroscopic information. The measured angular distribution for the He-6 + Li-6 --> alpha + Li-8 reaction indicated close similarity between the alpha + 2n configuration in He-6 and the alpha + d configuration in Li-6. The obtained results for alpha-particle pickup from both Li-6 and Li-7 give large values of a spectroscopic factors for some Be-10 states, indicating their well-developed alpha + He-6 cluster structure. The exotic two-proton pickup reaction (He-6, Be-8) was studied, as well as two-neutron and triton transfer reactions. Quasi-free scattering of He-6 on deuteron and a particle in Li-6 was also observed. The sequential decay reactions He-6 + Li-6 --> He-6 + alpha + d, He-6 + Li-6 --> 2 alpha + t + n, He-6 + Li-7 --> He-6 + alpha + t, and He-6 + C-12 --> Be-10 + 2 alpha were clearly seen, and alpha clustering of some states in Li-6,Li-7, Be8-10, and C-14 was thus studied. Several new spectroscopic results obtained for some Be-10 states support the existence of a molecule-like rotational band in Be-10 with a very large moment of inertia.

Backpack Moment of Inertia Affects Oxygen Consumption During Walking

Prior research on the metabolic energy cost of carrying backpack loads has focused primarily on the effects of weight carried on the rate of oxygen consumption during walking. However, less research has been done on the effects of manipulating backpack mass center location or moment of inertia (MOI) on oxygen consumption. PURPOSE: The purpose of this study was to examine the effects of manipulating the MOI (distribution of mass about an axis of rotation) of a backpack load on the rate of oxygen consumption during walking. We hypothesized that varying the relationships among MOI values for the principal axes would differentially affect oxygen consumption. METHODS: Fourteen male volunteers participated in the study. Steel weights (26 kg total mass) were positioned in each of three military backpacks to produce different MO Is, but with the same mass (35 kg, inclusive of the backpack) and mass center locations (0.3 m posterior to the pack frame and 0.3 m superior to the bottom of the pack). The three packs differed in that each had the MOI of a unique principal axis (Ixx, Iyy, Izz) set at a small value (< 1.0 kg.m2), while the other two principal axes had large moments of inertia (> 2.0 kg.m2). Relative to the load carrier's body, Ixx, Iyy, and Izz defined the MOI about the anterior-posterior axis, the medial-lateral axis, and the vertical axis, respectively. The volunteers walked on a level treadmill at 4.8 km/h for 10 min carrying each of the packs. The rate of oxygen consumption (VO2) was recorded (COSMED K4b2, COSMED, Rome, Italy) during the last 90 sec of the walking period and was scaled to body plus load mass. A repeated measures ANO VA with three levels of MOI and follow-up comparisons were used to assess differences in the mean mass specific VO2. RESULTS: A significant difference (p < .05) in mean mass specific VO2 was found between the small Ixx value pack (15.04 ml/kg/min (SD 1.96)) and the small Iyy value pack (16.27 ml/kg/min (SD 2.09)). Mean differences approached statistical significance (p = .061) between the small Ixx pack and the small Izz pack (16.15 ml/kg/min (SD 2.23)). The small Iyy value and small Izz value packs did not statistically differ. CONCLUSION: The mean mass specific rate of oxygen consumption was 7.6% lower when Ixx was minimized relative to Iyy. Therefore, the metabolic energy cost of carrying backpack loads is not solely dependent on the amount of mass carried. The manner in which items are stowed in the backpack also affects metabolic energy expenditure and thus the physical endurance of the load carrier.