Satellite triangulation in Europe from WEST and ISAGEX data

Observational data that was acquired during the West European Satellite Triangulation (WEST) program and the International Satellite Geodesy Experiment (ISAGEX) campaign was obtained for the purpose of performing a geometric solution to improve the present values of coordinates of the European stations in the OSU WN14 solutions, adding some new stations and assessing the quality of the WN14 solution with the help of the additional data available. The status of the data as received, the preprocessing required and the preliminary tests carried out for the initial screening of the data are described. The adjustment computations carried out and the results of the adjustments are discussed

NASTRAN implementation of an isoparametric doubly-curved quadrilateral shell element

A quadrilateral shell element, CQUAD4, was added to level 15.5 and subsequently to level 16.0 of NASTRAN. The element exhibited doubly curved surfaces and used biquadratic interpolation functions. Reduced integration techniques were used to improve the performance of the element in thin shell problems. The creation of several new bulk data items is discussed, along with a special module, GPNORM, to process SHLNORM bulk data cards. In addition to the theoretical basis for the element stiffness matrix, consistent mass and load matrices are presented. Several potential sources of degenerate behavior of the element were investigated. Guidelines for proper use of the element were suggested. Performance of the element on several widely published classical examples was demonstrated. The results showed a significant improvement over presently available NASTRAN shell elements for even the coarsest meshes. Potential applications to two classes of practical problems are discussed

Complex Master Slave Interferometry

A general theoretical model is developed to improve the novel Spectral Domain Interferometry method denoted as Master/Slave (MS) Interferometry. In this model, two functions, g and h are introduced to describe the modulation chirp of the channeled spectrum signal due to nonlinearities in the decoding process from wavenumber to time and due to dispersion in the interferometer. The utilization of these two functions brings two major improvements to previous implementations of the MS method. A first improvement consists in reducing the number of channeled spectra necessary to be collected at Master stage. In previous MSI implementation, the number of channeled spectra at the Master stage equated the number of depths where information was selected from at the Slave stage. The paper demonstrates that two experimental channeled spectra only acquired at Master stage suffice to produce A-scans from any number of resolved depths at the Slave stage. A second improvement is the utilization of complex signal processing. Previous MSI implementations discarded the phase. Complex processing of the electrical signal determined by the channeled spectrum allows phase processing that opens several novel avenues. A first consequence of such signal processing is reduction in the random component of the phase without affecting the axial resolution. In previous MSI implementations, phase instabilities were reduced by an average over the wavenumber that led to reduction in the axial resolution

Internationalisierungspfade mittelständischer Unternehmen in Osteuropa: Internationalisierungsprozess und Standorteffekte am Beispiel niedersächsischer KMU

Für westeuropäische Unternehmen im Allgemeinen und für westeuropäische kleine und mittlere Unternehmen (KMU) im Besonderen bildete die politische und wirtschaftliche Marktöffnung in Mittel- und Osteuropa (MOE) zu Beginn der 1990er Jahre und die Integration vieler dieser Transformationsländer in die EU einen wichtigen Anlass, ihre Aktivitäten in der Großregion MOE zu verstärken. Das Ziel der Studie ist es, die Spezifika des Markteintritts, die Rolle von Barrieren beim Markteintritt und im Verlauf der Internationalisierung sowie mögliche Standorteffekte zu analysieren. Die Studie basiert auf Fallstudien in KMU mit Sitz in Niedersachsen, die bereits Märkte in MOE erschlossen haben. Den theoretisch-konzeptionellen Hintergrund bilden zwei gängige Modelle der Internationalisierung: das Prozessmodell und der Netzwerkansatz. Als Ergebnis zeigt sich, dass beide Modelle den Internationalisierungsverlauf der betrachteten Unternehmen nur unzureichend beschreiben. Vielmehr beeinflusst ein Mix unterschiedlicher Faktoren den Markteintritt wie die Marktbearbeitung im Zeitverlauf. Als Tendenz ist gleichwohl feststellbar, dass sich die Bedeutung von Barrieren beim Markteintritt in MOE seit dem EU-Beitritt vieler MOE-Länder abgeschwächt hat.The political and economic transformation and market opening in Central Eastern Europe (CEE) at the beginning of the 1990s as well as the EU enlargement gave reason for Western European firms in general and Western European small and medium-sized enterprises (SMEs) in particular to increase their activities in these countries. The objective of the study is to explore patterns concerning their market entries, market development, barriers encountered and the potential locational effects of business activities in CEE. The study is based on cases studies in SMEs located in the Federal State of Lower Saxony, which have already entered CEE markets. As theoretical background we use two established models of the internationalization of SMEs, i.e., the process or stage model, and the network approach to internationalization. Our findings suggest, however, that the basic contentions made by these models on the internationalization path of SMEs should be complemented with a broader perspective that takes into consideration a variety of additional factors. As a general tendency, we find nonetheless evidence that the intensity of market entry barriers in CEE has decreased since and, obviously, due to EU enlargement

Investigation into the effect of atmospheric particulate matter (PM2.5 and PM10) concentrations on GPS signals

The Global Positioning System (GPS) has been widely used in navigation, surveying, geophysical and geodynamic studies, machine guidance, etc. High-precision GPS applications such as geodetic surveying need millimeter and centimeter level accuracy. Since GPS signals are affected by atmospheric effects, methods of correcting or eliminating ionospheric and tropospheric bias are needed in GPS data processing. Relative positioning can be used to mitigate the atmospheric effect, but its efficiency depends on the baseline lengths. Air pollution is a serious problem globally, especially in developing countries that causes health problems to humans and damage to the ecosystem. Respirable suspended particles are coarse particles with a diameter of 10 micrometers or less, also known as PM10. Moreover, fine particles with a diameter of 2.5 micrometers or less are known as PM2.5. GPS signals travel through the atmosphere before arriving at receivers on the Earth’s surface, and the research question posed in this paper is: are GPS signals affected by the increased concentration of the PM2.5/PM10 particles? There is no standard model of the effect of PM2.5/PM10 particles on GPS signals in GPS data processing, although an approximate generic model of non-gaseous atmospheric constituents (<1 mm) can be found in the literature. This paper investigates the effect of the concentration of PM2.5/PM10 particles on GPS signals and validates the aforementioned approximate model with a carrier-to-noise ratio (CNR)-based empirical method. Both the approximate model and the empirical results show that the atmospheric PM2.5/PM10 particles and their concentrations have a negligible effect on GPS signals and the effect is comparable with the noise level of GPS measurements

Mode Division Multiplexing Exploring Hollow-Core Photonic Bandgap Fibers

We review our recent exploratory investigations on mode division multiplexing using hollow-core photonic bandgap fibers (HC-PBGFs). Compared with traditional multimode fibers, HC-PBGFs have several attractive features such as ultra-low nonlinearities, low-loss transmission window around 2 μm etc. After having discussed the potential and challenges of using HC-PBGFs as transmission fibers for mode multiplexing applications, we will report a number of recent proof-of-concept results obtained in our group using direct detection receivers. The first one is the transmission of two 10.7 Gbit/s non-return to zero (NRZ) data signals over a 30 m 7-cell HC-PBGF using the offset mode launching method. In another experiment, a short piece of 19-cell HC-PBGF was used to transmit two 20 Gbit/s NRZ channels using a spatial light modulator for precise mode excitation. Bit-error-ratio (BER) performances below the forward-error-correction (FEC) threshold limit (3.3×10-3) are confirmed for both data channels when they propagate simultaneously. © 2013 IEEE