Is rentier capitalism that bad? Rent, efficiency and inequality dynamics

Abstract. The current economic context shows a tendency to inequality and rather weak growth. Rent-seeking behavior is often blamed for that. The purpose of this paper is to analyze the consequences, on the accumulation trajectory, of the existence of a rent levied by the rich on the poor. The model is inspired by the articles Stiglitz (1969), Schilcht (1975) and Bourguignon (1981). In particular, convex saving is used. We seek to see to what extent the introduction of a rent may call into question the Pareto-superiority of inequality proved by Bourguignon (1981) or alter the risk of decline highlighted in Mabrouk (2016). Within the limits of the assumptions of the model and of the numerical simulations carried out, we arrive at interesting and rather unexpected observations. Namely, a moderate rent levied by the rich on the poor may not only allow a Pareto-improvement of the economy and prevent the risk of decline, but also, it may unlock the economy from under-accumulation trap even if initial capital endowment is insufficient. The disadvantages of such a rent for the poor are felt only if the economy approaches or exceeds the golden rule where the net marginal productivity of capital is zero.Keywords. Inequality dynamics, Neoclassical growth, Rent, Efficiency.JEL. D99, E13, E21, E22, O41

Les Cynipidae des chênes (Hymenoptera) collectés dans la chaîne montagneuse de Khmir (Tunisie) et mise à jour des connaissances sur les Cynipini tunisiens

Dans la présente étude réalisée dans le massif forestier de Khmir (aussi connu sous le nom de Kroumirie), on note les espèces gallicoles Cynipidae récoltées sur Quercus suber, Q. faginea et Q. coccifera. Au total, 20 espèces ont été trouvées dont huit sont citées pour la première fois de Tunisie : Andricus burgundus, A. curvator, A. quercusradicis, Cynips disticha, C. quercus, Neuroterus anthracinus, Plagiotrochus coriaceus et P. gallaeramulorum. La liste complète des Cynipini présents en Tunisie comprend 24 espèces. La mise à jour des connaissances sur ce groupe d'hyménoptères associés au genre sur Quercus a révélé que la présence d'Andricus infectorius (Hartig, 1843) citée depuis longtemps par les auteurs reste à discuter.En aquest estudi en el bosc de Khmir (també conegut pel Kroumirie), s'esmenten les espècies de cinípids cecidògens col·lectats en Quercus suber, Q. faginea i Q. coccifera. Un total de 20 espècies han estat trobades, vuit dels quals són esmentades per primera vegada a Tunísia: Andricus burgundus, A. curvator, A. quercusradicis, Cynips disticha, C. quercus, Neuroterus anthracinus, Plagiotrochus coriaceus i P. gallaeramulorum. La llista completa dels Cynipini presents a Tunísia contempla 24 espècies. La posada al dia del coneixement actualitzat d'aquest grup d'himenòpters sobre Quercus revela que la presència d'Andricus infectorius (Hartig, 1843), espècie esmentada des d'antic, necessita ser revisad

Millimeter-Wave Massive MU-MIMO Performance Analysis for Private Underground Mine Communications

In this article, a performance analysis of millimeter wave (mmWave) massive multiuser multiple-input and multiple-output (MU-MIMO) channel within an underground mine is performed. The analysis is based on channel measurements conducted at 28 GHz using a base station of 64 virtual antenna elements serving multiple users. Channel characteristics such as large-scale path loss, time dispersion, coherence bandwidth and sum-rate capacity are reported and evaluated. The results indicate that multislope path loss model is better suited for precise prediction of path loss across various propagation segments within the mining gallery. The time dispersion analysis reveals that the underground mine channel does not cause significant time dispersion, as 90% of the root-mean-square (rms) delay spreads are below 4 ns. In addition, it was found that the rms delay spread is not dependent on the propagation distance. The study on sum-rate capacity highlights the potential of employing massive MIMO technology to improve the channel’s spectral efficiency. The analysis reveals that the capacity, with eight active users, can reach up to 33.54 bit/s/Hz. The outcomes of this article offer valuable insights into the propagation properties of underground mine environment, which is characterized by rich-scattering and irregular topology

A Systematic Design of a Compact Wideband Hybrid Directional Coupler Based on Printed RGW Technology

Printed ridge gap waveguide (PRGW) is considered among the state of art guiding technologies due to its low signal distortion and low loss at Millimeter Wave (mmWave) spectrum, which motivates the research community to use this guiding structure as a host technology for various passive microwave and mmWave components. One of the most important passive components used in antenna beam-switching networks is the quadrature hybrid directional coupler providing signal power division with 90° phase shift. A featured design of a broadband and compact PRGW hybrid coupler is propose in this paper. A novel design methodology, based on mode analysis, is introduced to design the objective coupler. The proposed design is suitable for mmWave applications with small electrical dimensions ( 1.2λo×1.2λo ), low loss, and wide bandwidth. The proposed hybrid coupler is fabricated on Roger/RT 6002 substrate material of thickness 0.762 mm. The measured results highlight that the coupler can provide a good return loss with a bandwidth of 26.5% at 30 GHz and isolation beyond 15 dB. The measured phase difference between the coupler output ports is equal 90∘± 5∘ through the interested operating bandwidth. A clear agreement between the simulated and the measured results over the assigned operating bandwidth has been illustrated