GPS radio occultation with GRACE: Atmospheric profiling utilizing the zero difference technique

Radio occultation events recorded on 28-29 July 2004 by a GPS receiver aboard the GRACE-B satellite are analyzed. The stability of the receiver clock allows for the derivation of excess phase profiles using a zero difference technique, rendering the calibration procedure with concurrent observations of a reference GPS satellite obsolete. 101 refractivity profiles obtained by zero differencing and 96 profiles calculated with an improved single difference method are compared with co-located ECMWF meteorological analyses. Good agreement is found at altitudes between 5 and 30 km with an average fractional refractivity deviation below 1% and a standard deviation of 2-3%. Results from end-to-end simulations are consistent with these observations.Comment: 17 pages, 4 figure

Global monitoring of tropospheric water vapor with GPS radio occultation aboard CHAMP

The paper deals with application of GPS radio occultation (RO) measurements aboard CHAMP for the retrieval of tropospheric water vapor profiles. The GPS RO technique provides a powerful tool for atmospheric sounding which requires no calibration, is not affected by clouds, aerosols or precipitation, and provides an almost uniform global coverage. We briefly overview data processing and retrieval of vertical refractivity, temperature and water vapor profiles from GPS RO observations. CHAMP RO data are available since 2001 with up to 200 high resolution atmospheric profiles per day. Global validation of CHAMP water vapor profiles with radiosonde data reveals a bias of about 0.2 g/kg and a standard deviation of less than 1 g/kg specific humidity in the lower troposphere. We demonstrate potentials of CHAMP RO retrievals for monitoring the mean tropospheric water vapor distribution on a global scale.Comment: 7 pages, 4 figure

Inverse dynamic equilibrium analysis of mechanical systems undergoing prescribed rotational motions

Mechanical systems that undergo prescribed rotational motions arise in such engineered systems as robots, spacecraft, propulsion and power generation systems, and certain sensors and actuators. In order to avoid the resonance or the critical speed of the system and to keep the desired dynamic equilibrium state in the mechanical system undergoing rotational motions, the system’s design parameter values or driving angular speed should be tuned. In this work, a general formulation for the inverse dynamic equilibrium analysis is developed to directly calculate the driving angular speed or design parameter values which satisfy the condition of the desired dynamic equilibrium positions. The method is based upon the use of relative coordinates and a velocity transformation technique, and it is applicable to multibody systems having either open or closed loop configurations. To illustrate the method’s effectiveness, accuracy, and computational efficiency, two numerical examples are considered, and the results obtained analytically are compared with those obtained by using a commercial program’s transient analysis. In some cases, the equilibrium configuration is shown to have an operating condition for which the response has nearly zero standard deviations for small perturbations in a design parameter’s value. In that case, to verify the method’s effectiveness and usefulness, Monte-Carlo simulation results are shown

Can GNSS reflectometry detect precipitation over oceans?

For the first time, a rain signature in Global Navigation Satellite System Reflectometry (GNSS‐R) observations is demonstrated. Based on the argument that the forward quasi‐specular scattering relies upon surface gravity waves with lengths larger than several wavelengths of the reflected signal, a commonly made conclusion is that the scatterometric GNSS‐R measurements are not sensitive to the surface small‐scale roughness generated by raindrops impinging on the ocean surface. On the contrary, this study presents an evidence that the bistatic radar cross section σ0 derived from TechDemoSat‐1 data is reduced due to rain at weak winds, lower than ≈ 6 m/s. The decrease is as large as ≈ 0.7 dB at the wind speed of 3 m/s due to a precipitation of 0–2 mm/hr. The simulations based on the recently published scattering theory provide a plausible explanation for this phenomenon which potentially enables the GNSS‐R technique to detect precipitation over oceans at low winds

Evaluation of E Layer Dominated Ionosphere Events Using COSMIC/FORMOSAT-3 and CHAMP Ionospheric Radio Occultation Data

At certain geographic locations, especially in the polar regions, the ionization of the ionospheric E layer can dominate over that of the F2 layer. The associated electron density profiles show their ionization maximum at E layer heights between 80 and 150 km above the Earth’s surface. This phenomenon is called the “E layer dominated ionosphere” (ELDI). In this paper we systematically investigate the characteristics of ELDI occurrences at high latitudes, focusing on their spatial and temporal variations. In our study, we use ionospheric GPS radio occultation data obtained from the COSMIC/FORMOSAT-3 (Constellation Observing System for Meteorology, Ionosphere, and Climate/Formosa Satellite Mission 3) and CHAMP (Challenging Minisatellite Payload) satellite missions. The entire dataset comprises the long period from 2001 to 2018, covering the previous and present solar cycles. This allows us to study the variation of the ELDI in different ways. In addition to the geospatial distribution, we also examine the temporal variation of ELDI events, focusing on the diurnal, the seasonal, and the solar cycle dependent variation. Furthermore, we investigate the spatiotemporal dependency of the ELDI on geomagnetic storms

Perfil profissional dos trabalhadores na percepção de gestores de empresas do Vale do Taquari-RS

A competência profissional vem sendo considerada um fator essencial para a competitividade das empresas, que sofrem constantes mudanças estabelecidas pelo ambiente em que estão inseridas. Neste contexto, o objetivo desta pesquisa, de abordagem quantitativa e descritiva, foi identificar o perfil profissional dos trabalhadores requerido pelos gestores de empresas do Vale do Taquari-RS. Por meio de um questionário estruturado, com uma amostra de 67 gestores de empresas dos segmentos industrial, comercial e de prestação de serviços, os dados foram coletados e, após, analisados através da técnica estatística média ponderada. Os resultados oferecem indícios de que o perfil profissional dos trabalhadores, na percepção de gestores, é deficitário

Lateral Vibration and Read/Write Head Servo Dynamics in Magnetic Tape Transport

Magnetic tape is a flexible mechanical structure having dimensions that areorders of magnitude different in its thickness, width, and length directions. In order to position the tape relative to the read/write head, guides constrain the tape\u27s lateral motion, but even the modest forces that develop during guiding can cause wear and damage to the tape\u27s edges. This paper presents antensioned axially-moving viscoelastic Euler–Bernoulli beam model used to simulate thentape\u27s lateral dynamics, the guiding forces, and the position errornbetween the data tracks and the read/write head. Lateral vibration can be excited by disturbances in the form of pack runout, flange impacts, precurvature of the tape in its natural unstressed state, and spiral stacking as tape winds onto the take-up pack. The guide model incorporates nonlinear characteristics including preload and deadbands in displacement and restoring force. A tracking servo model represents the ability of the read/write head\u27s actuator to track disturbances in the tape\u27s motion, and the actuator\u27s motion couples through friction with the tape\u27s vibration. Low frequency excitation arising from pack runout can excite high frequency position error because of the nonlinear characteristics of the guides and impacts against the pack\u27s flanges. The contact force developed between the tape and the packs\u27 flanges can be minimized without significantly increasing the position error by judicious selection of the flanges\u27 taper angle

Exploring the internal dynamics of corporate social responsibility implementation : the role of resource endowments and functional departments

The way corporate social responsibility (CSR) strategies unfold inside organizations remains a black box. This qualitative study delves into the inner workings of CSR. We inductively investigate the role of tangible and intangible resources and how resource flows are linked to various organizational departments involved in the execution of CSR. Our research question is: How are resources allocated for CSR distributed among organizational departments and why do these resources shift in the course of CSR implementation? We find six mechanisms explaining why resources are dynamically allocated to different departments and why such resource shifts trigger organizational transition towards more advanced levels of CSR implementation. Our research contributes to the literature that examines how CSR activities and strategies unfold within businesses. More generally, this allows better understanding of intra-organizational dynamics of firms’ strategic responses to normative pressures

Finite Element Model for Hysteretic Friction Damping of Traveling Wave Vibration in Axisymmetric Structures

A finite element method is developed to treat the steady-state vibration of two axisymmetric structures—a base substructure and an attached dampersubstructure—that are driven by traveling wave excitation and that couplethrough a spatially distributed hysteretic friction interface. The base substructure is representative of a rotating brake rotor or gear, and the damper is a ring affixed to the base under preload and intended to control vibration through friction along the interface. In the axisymmetric approximation, the equation of motion of each substructure is reduced in order to the number of nodal degrees of freedom through the use of a propagation constant phase shift. Despite nonlinearity and with contact occurring at an arbitrarily large number of nodal points, the response duringsticking, or during a combination of sticking and slipping motions, can be determined from a low-order set of computationally tractable nonlinear algebraic equations. The method is applicable to element types for longitudinal and bending vibration, and to an arbitrary number of nodal degrees of freedom in each substructure. In two examples, friction damping of the coupled base and damper is examined in the context of in-plane circumferential vibration (in which case the system is modeled as two unwrapped rods), and of out-of-plane vibration (alternatively, two unwrapped beams). The damper performs most effectively when its natural frequency is well below the base\u27s natural frequency (in the absence of contact), and also when its natural frequency is well separated from the excitationfrequency