27,313 research outputs found
An eco-solution for track & trace of goods and third party logistics
This paper presents a new economic cost-effective solution known as the Web and telephony based method for tracking and tracing of goods and small and medium sized third party logistic providers. Considering that these companies usually operate on very flat margins, a comparison is made of the available track and trace technologies like GPS, mobile phone approximated GPS and Java based cell tracking in terms of costs, operating risks, and other evaluation criteria
Robust model-based controller synthesis for the SCOLE configuration
The design of a robust compensator is considered for the SCOLE configuration using a frequency-response shaping technique based on the LQG/LTR algorithm. Results indicate that a tenth-order compensator can be used to meet stability-performance-robustness conditions for a 26th-order SCOLE model without destabilizing spillover effects. Since the SCOLE configuration is representative of many proposed spaceflight experiments, the results and design techniques employed potentially should be applicable to a wide range of large space structure control problems
Three dimensional thermal analysis of rocket thrust chambers
A numerical model for the three dimensional thermal analysis of rocket thrust chambers and nozzles has been developed. The input to the model consists of the composition of the fuel/oxidant mixture and flow rates, chamber pressure, coolant entrance temperature and pressure, dimensions of the engine, materials and the number of nodes in different parts of the engine. The model allows for temperature variation in three dimensions: axial, radial and circumferential directions and by implementing an iterative scheme, it provides nodal temperature distribution, rates of heat transfer, hot gas and coolant thermal and transport properties
Application of the LQG/LTR technique to robust controller synthesis for a large flexible space antenna
The problem of synthesizing a robust controller is considered for a large, flexible space-based antenna by using the linear-quadratic-Gaussian (LQG)/loop transfer recovery (LTR) method. The study is based on a finite-element model of the 122-m hoop/column antenna, which consists of three rigid-body rotational modes and the first 10 elastic modes. A robust compensator design for achieving the required performance bandwidth in the presence of modeling uncertainties is obtained using the LQG/LTR method for loop-shaping in the frequency domain. Different sensor actuator locations are analyzed in terms of the pole/zero locations of the multivariable systems and possible best locations are indicated. The computations are performed by using the LQG design package ORACLS augmented with frequency domain singular value analysis software
Calibrating the Cepheid Period-Luminosity relation with the VLTI
The VLTI is the ideal instrument for measuring the distances of nearby
Cepheids with the Baade-Wesselink method, allowing an accurate recalibration of
the Cepheid Period-Luminosity relation. The high accuracy required by such
measurement, however, can only be reached taking into account the effects of
limb darkening, and its dependence on the Cepheid pulsations. We present here
our new method to compute phase- and wavelength-dependent limb darkening
profiles, based on hydrodynamic simulation of Classical Cepheid atmospheres.Comment: 3 pages, 2 postscript figures, uses eas.cls LaTeX class file, to
appear in the proc. Eurowinter School "Observing with the VLTI", Feb 3-8
2002, Les Houches (France
Conditional operation of a spin qubit
We report coherent operation of a singlet-triplet qubit controlled by the
arrangement of two electrons in an adjacent double quantum dot. The system we
investigate consists of two pairs of capacitively coupled double quantum dots
fabricated by electrostatic gates on the surface of a GaAs heterostructure. We
extract the strength of the capacitive coupling between qubit and double
quantum dot and show that the present geometry allows fast conditional gate
operation, opening pathways to multi-qubit control and implementation of
quantum algorithms with spin qubits.Comment: related papers here: http://marcuslab.harvard.ed
Cruise report hydro acoustic survey for blue whiting (Micromesistius poutassou) with R.V. Tridens, 17 March - 04 April 2008
This is the report of the Dutch part of the international North East Atlantic hydro acoustic survey for blue whiting. The survey is coordinated by ICES and has been executed annually. The purpose of the survey is to estimate the blue whiting stock of the North East Atlantic. The ICES uses this estimation is as a “tuning index” to assess the North East Atlantic blue whiting stock. The applied method was echo integration. By sailing transects over the survey area, the total acoustic cross-section can be calculated by surface area sampled. Trawling identified species composition of localized schools. The length composition of each species was determined. Blue whiting was examined on age and fecundity from which a split up stock structure was mad
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