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In this paper, an L-DACS1 physical layer laboratory demonstrator is presented which has been implemented recently in FPGA technology by the German Aerospace Center (DLR). The main goal of this lab demonstrator is to perform first compatibility measurements between L-DACS1 and legacy L-band systems where interference from L-DACS1 towards the legacy systems as well as interference from the legacy systems onto the L-DACS1 receiver is considered. The lab demonstrator is already implemented up to the first intermediate frequency at 10.7 MHz. The radio frontend for up-/down-conversion to/from the Lband is scheduled to be delivered in May this year. First compatibility tests are planned to take place in the labs of the German ATC authority DFS this summer. Using real hardware equipment, these tests will give valuable insight into the L-band coexistence issue and possible deployment scenarios.

RGBW AMOLED panel, compare to the RGB panel, has lower power consumption and current stress and as result — bigger life time. Using special algorithms and RGB subpixels (as additional white) permits to increase brightness of this panel up to 2 times. At the same time it's very important to keep panel current at permissible range. We propose an algorithm, what permits to increase brightness of the RGBW AMOLED panel and limit its summary current at the same time.

The evaluation of the blading clearance at the design stage is important for heavy duty gas turbine efficiency. The minimum clearance value at base load is limited by the pinch point clearance during startup and/or shutdown. Therefore, transient analysis is necessary for different operating conditions. 3D transient analysis of a whole engine is labor-intensive; however 2D axisymmetric analysis does not allow consideration of different 3D effects (e.g. twisting, bending, ovality, rotor alignment). In order to overcome these cost and time limitations, the combination of 2D, axisymmetric, whole-engine model results and the scaled deflections caused by different 3D effects is used for the axial and radial clearance engineering assessment during engine operation. The basic rotor and stator closures are taken from the transient analysis using a 2D finite element (FE) model composed of axisymmetric solid and plane stress elements. To take into account 3D effects of airfoil twisting and bending, the 3D FE displacements of the blade are included in the clearance evaluation process. The relative displacements of airfoil tip and reference point at the blade or vane hub are taken from 3D steady-state FE analyses. Then the steady-state displacements of the airfoils are scaled for transient conditions using the proposed technique. Different 3D rotor / stator effects (cold-build clearances and their tolerances, rotor position with respect to stator after assembly, casing bending, deformations of compressor and turbine vane carrier inducing of casing ovalization, exhaust gas housing movements, movements of the rotor in bearings and CVC and TVC support, etc.) are also included as a contributor to the clearances. The results of the calculations are analyzed and compared with good agreements to the clearances measured in engine testing under real operation conditions. The proposed methodology allows assessing the operating clearances between the stator and rotor during the design phase. Optimization of the running clearance is one key measure to upgrade and improve the engine performance during operating experience.

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During the modernization of the low-pressure compressor of the regional aircraft engine, a flow separator made of polymer composite material was developed, which has less weight, is easier and cheaper to manufacture. However, the separator must undergo a series of tests before being installed on the engine, in particular the endurance tests, necessary to assess the fatigue strength margin. A method for determining the endurance limit of a large part of an aircraft engine is developed in the presented work and consists in replacing the tests of the entire separator with tests of individual structural elements cut from the part. The shape, dimensions and fixation of the elements have been chosen in such a way that their own test frequency was close to the natural frequency of the flow separator on the engine. The natural oscillation frequencies and places of maximum dynamic stresses have been determined before testing on three-dimensional models of the flow separator and elements cut from it. As a result, the structural elements have been tested until appearance of fatigue cracks which allowed to assess the endurance limit and evaluate fatigue strength margin of the separator.

The regional aircraft with a turbofan gas turbine engine, created in Russia, is successfully operated in the world market. Further increase of the life and reduction of the cost of the life cycle are necessary to ensure the competitive advantages of the engine. One of the units limiting the engine life is the compressor rotor. The cyclic life of the rotor depends on many factors: the stress-strain state in critical zones, the life of the material under low-cycle loading, the regime of engine operation, production deviations (within tolerances), etc. In order to verify the influence of geometry deviations, the calculations of the model with nominal dimensions and the model with the most unfavorable geometric dimensions (worst cases) have been carried out. The obtained influence coefficients for geometric and weight tolerances are then used for probabilistic modeling of stresses in the critical zone. Rotor speed and gas loads on the blades for different flight missions and engine wear are determined from the corresponding aerodynamic calculations taking into account the actual flight cycles (takeoff, reduction, reverse) and are also used for stress recalculations. The subsequent calculation of the rotor cyclic life and the resource assessment is carried out taking into account the spread of the material low-cycle fatigue by probabilistic modeling of the rotor geometry and weight loads. A preliminary assessment of the coefficients of tolerances influence on stress in the critical zone can be used to select the optimal (in terms of life) tolerances at the design stage. Taking into account the actual geometric and weight parameters can allow estimating the stress and expected life of each manufactured rotor.

This article investigates the influence of sampling time offset on the performance of an interleaved frequencydivision multiple-access (IFDMA) uplink scheme for mobile radio transmission. It is shown that sampling time offset causes signal-to-noise ratio (SNR) degradation and leads to intersymbol interference (ISI). In addition, an efficient algorithm is proposed which is capable to estimate sampling time offset by applying oversampling at the receiver. The proposed algorithm requires only three-times oversampling, does not use any pilot symbols, and is independent from the transmission channel and modulation alphabet.