In this paper, we define a new projective invariant and call it W̃ -curvature. We prove that a Finsler manifold with dimension n ≥ 3 is of constant flag curvature if and only if its W̃ -curvature vanishes. Various kinds of projectively flatness of Finsler metrics and their equivalency on Riemannian metrics are also studied. M.S.C. 2010: 53B40, 53C60.

We introduce the concept of flatness degree for matroids, as a generalization of submodularity. This represents weaker variations of the concept of flatness which characterize strict gammoids for finite matroids. We prove that having flatness degree 3, which is the smallest non-trivial flatness degree, implies pseudomodularity on the lattice of flats of the matroid. We show however an example o...

Valdis Laan in [5] introduced an extension of strong flatness which is called weak pullback flatness. In this paper we introduce a new property of acts over monoids, called U-WPF which is an extension of weak pullback flatness and give a classification of monoids by this property of their acts and also a classification of monoids when this property of acts implies others. We also show that regu...

This paper is devoted to the study of products of classes of right $S$-posets possessing one of the flatness properties and preservation of such properties under products. Specifically, we characterize a pomonoid $S$ over which its nonempty products as right $S$-posets satisfy some known flatness properties. Generalizing this results, we investigate products of right $S$-posets satisfying Condi...

lapping is one of the most important polishing processes which can be used to fabricate flat and smooth surfaces. in this paper, the effect of lapping characteristics and mesh number of abrasive particles are studied on the surface roughness and flatness for the machining of hardened aisi 52100 rings. the most significant lapping characteristics are pressure, lap plate speed and time. scanning ...

This paper presents a new realization method of broadband power amplifier based on novel filter matching network. The network band-pass has an excellent frequency-selection function, which can ensure the characteristics in aim band and generates out-of-band harmonic suppression. Finally, we manufactured measured it. saturated output is greater than 40 dBm range 1 to 3 GHz, limited ±1.5 dB gain ...

In this paper, we introduce a novel printed monopole antenna for ultra-wideband (UWB) applications. The antenna is composed of two overlapped circular disc monopoles with a finite ground plane and fed by a 50 microstrip line. The designed antenna operates over impedance bandwidth (2.9 to 11.6GHz) for return loss S Ω 11 < -10dB. The antenna also shows omni-directional radiation patterns and good...