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1

On Nörlund summation and ergodic theory, with applications to power series of Hilbert contractions

Cuny C., Weber M.

Bulletin of the Polish Academy of Sciences. Mathematics

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2018

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Vol. 66, no. 1

69--85

EN

We show that if a = (an)n∈N is a good weight for the dominated weighted ergodic theorem in Lp, p > 1, then the Nörlund matrix Na = {ai−j / Ai}0≤j≤i, Ai = ∑ik=0|ak|, is bounded on ℓp(N). We study the regularity (convergence in norm and almost everywhere) of operators in ergodic theory: power series of Hilbert contractions and power series ∑n∈N an Pn f of L2-contractions, and establish similar close relations to the Nörlund operator associated to the modulus coefficient sequence (|an|)n∈N.

2

The influence of high efficiency engines and hybrids on exhaust systems

Weber M.

Combustion Engines

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2017

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R. 56, nr 4

207--210

EN

Increased efficiency of the combustion process itself and low losses in the Engine, lead to lower temperatures in the exhaust line. Combined with the exhaust gas energy recovery as well as the hybridization of the drivetrain, this temperature decrease will require additional efforts for the exhaust gas aftertreatment in future. Current technologies like SCR with urea could only be used in future with additional heating elements or will need to change to different catalysts or gaseous Ammonia, to keep the current efficiency and conversion rates. Catalyst and filter elements with ultra-low backpressure creating additional new challenges for the correct and robust diagnostics of these aftertreatment components and all emission relevant parts and thresholds. New technologies are needed like the direct measurement of the DPF soot loading with radio frequencies or NH3 sensors to precisely control the ammonia slip for high conversion rates of SCR catalysts.

3

The potential of plasma deposition techniques in the application field of forging processes

Yilkiran T., Behrens B. A., Paschke H., Weber M., Brand H.

Archives of Civil and Mechanical Engineering

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2012

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Vol. 12, no. 3

284--291

EN

High mechanical, chemical and thermal cyclic loads characterize the load regime of hot forging applications. Additionally these loads are acting simultaneously which leads to a failure of the form giving tool components after a short tool life. Accounting for about 70% of all causes, wear is the main reason for production downtimes. Other failure factors are thermal and mechanical cracks as well as plastic deformation as a result of the loss of hardness due to the high thermal charge. The caused production downtimes can be reduced by surface modifications of the tools. Different results of recent research works prove the high potential of newly developed PVD and PECVD coating systems regarding the reduction of die wear. CrVN coating systems developed by PVD coating equipment and boron containing multilayered PECVD coating systems were applied to forging dies. Basic investigations of the occurring wear mechanisms show the qualification of the coating systems which have to be adapted to the decisive process related loads and damages.

4

Optimized plasma nitriding processes for efficient wear reduction of forging dies

Paschke H., Weber M., Braeuer G., Yilkiran T., Behrens B. A., Brand H.

Archives of Civil and Mechanical Engineering

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2012

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Vol. 12, no. 4

407--412

EN

Plasma nitriding treatments are approved to reduce wear occurring in the field of hot forging applications. But there are demands for a further optimization of the processes in order to achieve adapted properties for differently loaded forging tools. This work presents the influence of main process parameters on the wear behavior of dies. The focused steel material of this work is DIN-X38CrMoV5-1 (1.2343), a standard hot forming tool steel. The influence of nitriding parameters like temperature, nitrogen flow and time on the nitriding depth, hardness and crack sensitivity has been investigated. Comparative application tests show the influence of different surface treatments on the wear behavior and lifetime of forging tools in an industrial environment.

5

A sharp correlation inequality with application to almost sure local limit theorem

Weber M.

Probability and Mathematical Statistics

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2011

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Vol. 31, Fasc. 1

79--98

EN

We prove a new sharp correlation inequality for sums of i.i.d. square integrable lattice distributed random variables. We also apply it to establish an almost sure version of the local limit theorem for i.i.d. square integrable random variables taking values in an arbitrary lattice. This extends a recent similar result jointly obtained with Giuliano-Antonini under a slightly stronger absolute moment assumption (of order 2+u with u > 0). The approach used to treat the case u > 0 breaks down when u = 0. Mac- Donald’s concept of the Bernoulli part of a random variable is used in a crucial way to remedy this.