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Piecewise linear detection for direct superposition modulation

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Digital Communications and Networks 2018年第2期4卷 98-105页

作者： Martin Damrath Peter Adam Hoeher Gilbert J.M. Forkel Institute of Electrical and Information Engineering Faculty of Engineering University of Kiel Kaiserstr. 2 24143 Kiel Germany

Considering high-order digital modulation schemes, the bottleneck in consumer products is the detector rather than the modulator. The complexity of the optimal a posteriori probability （APP） detector increases exponentially with respect to the number of modulated bits per data symbol. Thus, it is necessary to develop low-complexity detection algorithms with an APP-like performance, especially when performing iterative detection, for example in conjunction with bit interleaved coded modulation. We show that a special case of superposition modulation, dubbed Direct Superposition Modulation （DSM）, is particularly suitable for complexity reduction at the receiver side. As opposed to square QAM, DSM achieves capacity without active signal shaping. The main contribution is a low-cost detection algorithm for DSM, which enables iterative detection by taking a priori information into account. This algorithm exploits the approximate piecewise linear behavior of the soft outputs of an APP detector over the entire range of detector input values. A theoretical analysis and simulation results demonstrate that at least max-log APP performance can be reached, while the complexity is significantly reduced compared to classical APP detection.

关键词： Digital modulation Demodulation Detection algorithms Linear approximation

Symbol detection based on Voronoi surfaces with emphasis on superposition modulation

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Digital Communications and Networks 2017年第3期3卷 141-149页

作者： Martin Damrath Peter Adam Hoeher Gilbert J.M. Forkel Institute of Electrical and Information Engineering Faculty of Engineering University of Kiel Kaiserstr. 2 24143 Kiel Germany

A challenging task when applying high-order digital modulation schemes is the complexity of the detector. Particularly, the complexity of the optimal a posteriori probability （APP） detector increases exponentially with respect to the number of bits per data symbol. This statement is also true for the Max-Log-APP detector, which is a common simplification of the APP detector. Thus it is important to design new detection algorithms which combine a sufficient performance with low complexity. In this contribution, a detection algorithm for two- dimensional digital modulation schemes which cannot be split-up into real and imaginary parts （like phase shift keying and phase-shifted snperposition modulation （PSM）） is proposed with emphasis on PSM with equal power allocation. This algorithm exploits the relationship between Max-Log-APP detection and a Voronoi diagram to determine planar surfaces of the soft outputs over the entire range of detector input values. As opposed to state-of-the-art detectors based on Voronoi surfaces, a priori information is taken into account, enabling iterative processing. Since the algorithm achieves Max-Log-APP performance, even in the presence of a priori information, this implies a great potential for complexity reduction compared to the classical APP detection.

关键词： Digital modulation Demodulation Detection algorithms Linear approximation

从煤焦油软沥青和苯基硅烷制备硅取代聚芳烃中间相的研究(英文)

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新型炭材料 2003年第2期18卷 1-9页

作者： J. Schwendinger W.G. Zhang K.J. Hüttinger Institut für Chemische Technik Universitt KarlsruheInstitut für Chemische Technik Universitt KarlsruheInstitut für Chemische Technik Universitt Karlsruhe Kaiserstr. 12 76128 Karlsruhe Germany Kaiserstr. 12 76128 Karlsruhe Germany Kaiserstr. 12 76128 Karlsruhe Germany

　过滤后的煤焦油沥青分别与一,二,三,四苯基硅烷在1MPa氩气气氛和420℃～460℃温度下共炭化,合成了硅取代聚芳烃中间相。在四种合成中间相中,元素硅的起始加入量均为2%。测定了裂解残留物和硅的收率、可溶性、玻璃转化温度以及裂解残... 详细信息

　过滤后的煤焦油沥青分别与一,二,三,四苯基硅烷在1MPa氩气气氛和420℃～460℃温度下共炭化,合成了硅取代聚芳烃中间相。在四种合成中间相中,元素硅的起始加入量均为2%。测定了裂解残留物和硅的收率、可溶性、玻璃转化温度以及裂解残留物的炭收率;并分别以偏光显微镜和电子探针微分析法考察了残留物的微结构和相应的硅分布,硅的收率取决于不同的苯取代硅烷的挥发性和反应性。裂解残留物显示出三种不同的共存相:(a)含有粗镶嵌织构和痕量硅的光学各向异性相;(b)硅含量较高的光学各向同性相;(c)含细镶嵌织构和中等硅含量的光学各向异性相。最后这种中间相主要来自二,三苯取代硅烷与煤沥青的共炭化,是由于硅取代聚芳烃中碳原子并破坏了其分子的平面结构而引起的。

关键词：煤焦油软沥青苯基硅烷制备硅聚芳烃中间相取代研究热解微结构煤焦油沥青

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Experimental and Analytical Analysis of Perforated Plate Aerodynamics

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Journal of Thermal Science 2003年第3期12卷 193-197页

作者： JürgenZierep RainerBohning Piotr Doerffer ISL Karlsruhe University Kaiserstr.12 D-76 128 Karsruhe GermanyISL Karlsruhe University Kaiserstr.12 D-76 128 Karsruhe GermanyIMP PAN Fiszera 14 PL-80 952 Gdansk Poland

Perforated walls and transpiration flow play an important role in aerodynamics due to an increasing interest in application of flow control by means of blowing and/or suction. An experimental study was carried out which has led to the determination of a transpiration flow characteristics in the form of a simple formula that is very useful in modelling such flows. In connection to this relation a method of 'aerodynamic porosity' determination has been proposed which is much more reliable than geometric description of the porosity. A theoretical analysis of the flow through a perforation hole was also carried out. The flow was considered as compressible and viscous. The gasdynamic analysis led us to a very similar result to the relation obtained from the experiment. The adequacy of the theoretical result is discussed in respect to the experiment.

关键词： transonic flow flow control transpiration flow perforated walls blowing and suction.

Visualization of Unsteady Gas/Vapor Expansion Flows

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Journal of Thermal Science 1997年第3期6卷 171-180页

作者： G.H.Schnerr S.Adam InstitutfuerStroemungsmaschinen UniversitaetKarlsruhe（TH）Kaiserstr12D－76128KarlsruheGermany Insti

High speed expansion flows of pure vapors or gas/vapor mixtures are important to many technical applications, e.g. to steam turbines, jet engines, and for safety control of pressurized power *** sudden cooling of the fluid flow leads to condensation and nonequilibrium two-phase now with instabilities and periodic shock formation at mean frequencies of about 1 kHz. Modelling and control of this dynamical problem is not only important with respect to erosion, it also may cause flutter excitation and serious demolition of technical facilities. In numerical simulations, the time dependent 2-D Elller equations collpled to four equations describing the process of homogeneous nucleation and droplet growth are solved by a MUSCL-type finite volume method. The results are compared with experiments carried out in an atmospheric supersonic wind tunnel. By application of this numerical method to internal flows (nozzles) we found different modes of instabilities including bifurcations. At the stability limit a sharp frequency minimum was found for symmetric oscillations in slender nozzles. It separates oscillation modes where the oncoming subsonic flow remains unchanged from the oscillatory state where a shock monotonically moves upstream into the oncoming flow. For different nozzles we detected a new unsymmetric oscillation mode with a complex system of upstream moving oblique shocks. Here the frequency curve shows the typical structure of a bifurcation problem, which is definitely not controlled by viscous effects but by instabilities of the interaction of flow and phase transition process.

关键词： two-phase flow instability oscillation compressible flow CFD nozzle flow

Shock Wave-Boundary Layer Interaction in Forced Shock Oscillations

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Journal of Thermal Science 2003年第1期12卷 10-15页

作者： Piotr Doerffer Oskar Szulc Franco Magagnato Institute of Fluid-Flow Machinery Polish Academy of Sciences Fiszera 14Institute of Fluid-Flow Machinery Polish Academy of Sciences Fiszera 14Institute fur Stromungslehre Universitat Karlsruhe Kaiserstr. 12 80-952 Gdansk Poland 80-952 Gdansk Poland D-76128 Karlsruhe Germany

The flow in transonic diffusers as well as in supersonic air intakes becomes often unsteady due to shock wave boundary layer interaction. The oscillations may be induced by natural separation unsteadiness or may be forced by boundary conditions. Significant improvement of CFD tools, increase of computer resources as well as development of experimental methods have *** the attention of researchers to this topic. To investigate the problem forced oscillations of transonic turbulent flow in asymmetric two-dimensional Laval nozzle were considered. A viscous, perfect gas flow, was numerically simulated using the Reynolds-averaged compressible Navier-Stokes solver SPARC, employing a two-equation, eddy viscosity, turbulence closure in the URANS *** time-dependent and stationary flow simulations, Mach numbers upstream of the shock between 1.2 and 1.4 were considered. Comparison of computed and experimental data for steady states generally gave acceptable agreement. In the case of forced oscillations, a harmonic pressure variation was prescribed at the exit plane resulting in shock wave motion. Excitation frequencies between 0 Hz and 1024 Hz were investigated at the same pressure *** main result of the work carried out is the relation between the amplitude of the shock wave motion and the excitation frequency in the investigated range. Increasing excitation frequency resulted in decreasing amplitude of the shock movement. At high frequencies a natural mode of shock oscillation (of small amplitude) was observed which is not sensitive to forced excitement.

关键词： unsteady transonic flow shock wave nozzle flow.

INFLUENCE OF SEDIMENT TRANSPORT ON ARMORED SURFACES

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International Journal of Sediment Research 2001年第2期16卷 201-206页

作者： Katinka KOLL1and Andreas DITTRICH1 1 Institute of Resources Management, Hydraulic and Rural Engineering, University of Karlsruhe, kaiserstr. 12, 76128 Karlsruhe, Germany. Institute of Resources Management Hydraulic and Rural Engineering University of Karlsruhe Kaiserstr. 1276128 Karlsruhe Germany.

Laboratory experiments have been carried out to study the characteristics of sediment transport in steep streams. The question is discussed wether an armoured surfaces is destroyed due to the transport of material, because additional impulses are acting on it, or the layer is sheltered by the transported material, because a part of the stream power is used to move the material. According to the results of the presented experiments, in which the influence of the feeding rate and the feeding duration have been investigated, transported material reaching an armoured river section from upstream always remobilzes bed material, which is immobile under clear water flow conditions. To decide if a static armour layer is either destroyed or not, two simple criteria were chosen: one considering the grain-size distribution of the eroded bed material, and another, which referes to the amount of eroded bed material.

关键词： Sediment transport Bed stability Armored layer

A Novel Approach to Predict the Stability Limits of Combustion Chambers with Large Eddy Simulation

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Journal of Thermal Science 2010年第3期19卷 261-265页

作者： B.Pritz F.Magagnato M.Gabi Department of Fluid Machinery University of Karlsruhe Kaiserstr.1276131 KarlsruheGermany

Lean premixed combustion,which allows for reducing the production of thermal NOx,is prone to combustion *** is an extensive research to develop a reduced physical model,which allows-without time-consuming measurements-to calculate the resonance characteristics of a combustion system consisting of Helmholtz resonator type components (burner plenum,combustion chamber).For the formulation of this model numerical investigations by means of compressible Large Eddy Simulation (LES) were carried *** these investigations the flow in the combustion chamber is isotherm,non-reacting and excited with a sinusoidal mass flow *** a combustion chamber as a single resonator subsequently a coupled system of a burner plenum and a combustion chamber were *** this paper the results of additional investigations of the single resonator are *** flow in the combustion chamber was investigated without excitation at the *** was detected,that the mass flow rate at the outlet cross section is pulsating once the flow in the chamber is *** fast Fourier transform of the signal showed that the dominant mode is at the resonance frequency of the combustion *** result sheds light on a very important source of self-excited combustion *** the LES can provide not only the damping ratio for the analytical model but the eigenfrequency of the resonator also.

关键词： compressible large-eddy simulation combustion instabilities oscillating flow damping ratio

Streamwise Vortex Interaction with a Horseshoe Vortex

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Journal of Thermal Science 2003年第4期12卷 304-309页

作者： Piotr Doerffer Pawel Flaszynski Franco Magagnato IMP PAN Fiszera 14 PL-80 952 Gdansk PolandIMP PAN Fiszera 14 PL-80 952 Gdansk PolandFGS Karlsruhe University Kaiserstr.12 D-76 128 Karlsruhe Germany

How control in turbomachinery is very difficult because of the complexity of its fully 3-D flow structure. The authors propose to introduce streamwise vortices into the control of internal flows. A simple configuration of vortices was investigated in order to better understand the flow control methods by means of streamwise vortices. The research presented here concerns streamwise vortex interaction with a horseshoe vortex. The effects of such an interaction are significantly dependent on the relative location of the streamwise vortex in respect to the leading edge of the profile. The streamwise vortex is induced by an air jet. The horseshoe vortex is generated by the leading edge of a symmetric profile. Such a configuration gives possibility to investigate the interaction of these two vortices alone. The presented analysis is based on numerical simulations by means of N-S compressible solver with a two-equation turbulence model.

关键词： flow control horseshoe vortex streamwise vortex.