Dynamics of early planetary gear trains

A method to analyze the static and dynamic loads in a planetary gear train was developed. A variable-variable mesh stiffness (VVMS) model was used to simulate the external and internal spur gear mesh behavior, and an equivalent conventional gear train concept was adapted for the dynamic studies. The analysis can be applied either involute or noninvolute spur gearing. By utilizing the equivalent gear train concept, the developed method may be extended for use for all types of epicyclic gearing. The method is incorporated into a computer program so that the static and dynamic behavior of individual components can be examined. Items considered in the analysis are: (1) static and dynamic load sharing among the planets; (2) floating or fixed Sun gear; (3) actual tooth geometry, including errors and modifications; (4) positioning errors of the planet gears; (5) torque variations due to noninvolute gear action. A mathematical model comprised of power source, load, and planetary transmission is used to determine the instantaneous loads to which the components are subjected. It considers fluctuating output torque, elastic behavior in the system, and loss of contact between gear teeth. The dynamic model has nine degrees of freedom resulting in a set of simultaneous second order differential equations with time varying coefficients, which are solved numerically. The computer program was used to determine the effect of manufacturing errors, damping and component stiffness, and transmitted load on dynamic behavior. It is indicated that this methodology offers the designer/analyst a comprehensive tool with which planetary drives may be quickly and effectively evaluated

Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation

We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. 2007 (Paper I). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of 13% including both statistical and systematic errors. We also constrain the halo concentration parameter and halo bias as a function of cluster mass; both are in good agreement with predictions of LCDM models. The methods employed here will be applicable to deeper, wide-area optical surveys that aim to constrain the nature of the dark energy, such as the Dark Energy Survey, the Large Synoptic Survey Telescope and space-based surveys

Gamma radiation survey of the LDEF spacecraft

The retrieval of the Long Duration Exposure Facility spacecraft in January 1990 after nearly six years in orbit offered a unique opportunity to study the long term buildup of induced radioactivity in the variety of materials on board. We conducted the first complete gamma-ray survey of a large spacecraft on LDEF shortly after its return to earth. A surprising observation was the Be-7 activity which was seen primarily on the leading edge of the satellite, implying that it was picked up by LDEF in orbit. This is the first known evidence for accretion of a radioactive isotope onto an orbiting spacecraft. Other isotopes observed during the survey, the strongest being Na-22, are all attributed to activation of spacecraft components. Be-7 is a spallation product of cosmic rays on nitrogen and oxygen in the upper atmosphere. However, the observed density is much greater than expected due to cosmic-ray production in situ. This implies transport of Be-7 from much lower altitudes up to the LDEF orbit

Membangun Sistem Kepartaian Pluralisme Moderat: Menyederhanakan Jumlah Partai Politik

Sistem kepartaian macam apakah yang senyatanya berlangsung di Indonesia dewasa ini? Setelah tiga kali pemilihan umum Pasca Orde Baru tampaknya sistem kepartaian yang berlangsung selama ini masih lebih banyak sebagai sumber masalah daripada solusi. Setidak-tidaknya terdapat sejumlah permasalahan yang berkaitan dengan sistem kepartaian di Indonesia yang berimbas terhadap fungsi sistem perwakilan rakyat dan efektivitas pemerintahan baik pada tingkat nasional maupun daerah

Menyetarakan Nilai Suara: Jumlah dan Alokasi Kursi DPR ke Provinsi

Salah satu prinsip pemilihan umum yang demokratis adalah equality atau kesetaraan. Maksudnya kesetaraan suara yang biasa diungkapkan dengan istilah OPOVOV: one person, one vote, one value. Prinsip ini menegaskan bahwa nilai suara yang dimiliki setiap pemilih adalah sama dalam satu pemilihan. Dalam perspektif hak warga negara, kesetaraan suara adalah perwujudan asas persamaan kedudukan warga negara dalam hukum dan pemerintahan. UUD 1945 mengakui bahwa “Segala warga negara bersamaan kedudukannya dalam hukum dan pemerintahan dan wajib menjunjung hukum dan pemerintahan itu dengan tidak ada kecualinya.

Dynamical Generation of Spacetime Signature by Massive Quantum Fields on a Topologically Non-Trivial Background

The effective potential for a dynamical Wick field (dynamical signature) induced by the quantum effects of massive fields on a topologically non-trivial $D$ dimensional background is considered. It is shown that when the radius of the compactified dimension is very small compared with $\Lambda^{1/2}$ (where $\Lambda$ is a proper-time cutoff), a flat metric with Lorentzian signature is preferred on ${\bf R}^4 \times {\bf S}^1$. When the compactification radius becomes larger a careful analysis of the 1-loop effective potential indicates that a Lorentzian signature is preferred in both $D=6$ and $D=4$ and that these results are relatively stable under metrical perturbations

Modeling the Near-Infrared Luminosity Functions of Young Stellar Clusters

We present the results of numerical experiments designed to evaluate the usefulness of near-infrared luminosity functions for constraining the Initial Mass Function (IMF) of young stellar populations. From this numerical modeling, we find that the luminosity function of a young stellar population is considerably more sensitive to variations in the underlying initial mass function than to either variations in the star forming history or assumed pre-main-sequence (PMS) mass-to-luminosity relation. To illustrate the potential effectiveness of using the KLF of a young cluster to constrain its IMF, we model the observed K band luminosity function of the nearby Trapezium cluster. Our derived mass function for the Trapezium spans two orders of magnitude in stellar mass (5 Msun to 0.02 Msun), has a peak near the hydrogen burning limit, and has an IMF for Brown Dwarfs which steadily decreases with decreasing mass.Comment: To appear in ApJ (1 April 2000). 37 pages including 11 figures, AAS: ver 5.

The nature of the dense core population in the pipe nebula: core and cloud kinematics from C18O observations

We present molecular-line observations of 94 dark cloud cores identified in the Pipe nebula through near-IR extinction mapping. Using the Arizona Radio Observatory 12m telescope, we obtained spectra of these cores in the J=1-0 transition of C18O. We use the measured core parameters, i.e., antenna temperature, linewidth, radial velocity, radius and mass, to explore the internal kinematics of these cores as well as their radial motions through the larger molecular cloud. We find that the vast majority of the dark extinction cores are true cloud cores rather than the superposition of unrelated filaments. While we identify no significant correlations between the core's internal gas motions and the cores' other physical parameters, we identify spatially correlated radial velocity variations that outline two main kinematic components of the cloud. The largest is a 15pc long filament that is surprisingly narrow both in spatial dimensions and in radial velocity. Beginning in the Stem of the Pipe, this filament displays uniformly small C18O linewidths (dv~0.4kms-1) as well as core to core motions only slightly in excess of the gas sound speed. The second component outlines what appears to be part of a large (2pc; 1000 solar mass) ring-like structure. Cores associated with this component display both larger linewidths and core to core motions than in the main cloud. The Pipe Molecular Ring may represent a primordial structure related to the formation of this cloud.Comment: Accepted to ApJ. 14 pages, 11 figures. Complete table at end of documen