Non-Orthogonal Multiple Access for FSO Backhauling

We consider a free space optical (FSO) backhauling system which consists of two base stations (BSs) and one central unit (CU). We propose to employ non-orthogonal multiple access (NOMA) for FSO backhauling where both BSs transmit at the same time and in the same frequency band to the same photodetector at the CU. We develop a dynamic NOMA scheme which determines the optimal decoding order as a function of the channel state information at the CU and the quality of service requirements of the BSs, such that the outage probabilities of both BSs are jointly minimized. Moreover, we analyze the performance of the proposed NOMA scheme in terms of the outage probability over Gamma-Gamma FSO turbulence channels. We further derive closed-form expressions for the outage probability for the high signal-to-noise ratio regime. Our simulation results confirm the analytical derivations and reveal that the proposed dynamic NOMA scheme significantly outperforms orthogonal transmission and existing NOMA schemes.Comment: This paper has been submitted to IEEE WCNC 201

Statistical Modeling of FSO Fronthaul Channel for Drone-based Networks

We consider a drone-based communication network, where several drones hover above an area and serve as mobile remote radio heads for a large number of mobile users. We assume that the drones employ free space optical (FSO) links for fronthauling of the users' data to a central unit. The main focus of this paper is to quantify the geometric loss of the FSO channel arising from random fluctuation of the position and orientation of the drones. In particular, we derive upper and lower bounds, corresponding approximate expressions, and a closed-form statistical model for the geometric loss. Simulation results validate our derivations and quantify the FSO channel quality as a function of the drone's instability, i.e., the variation of its position and orientation.Comment: This paper has been submitted to ICC 201

Criticality of natural absorbing states

We study a recently introduced ladder model which undergoes a transition between an active and an infinitely degenerate absorbing phase. In some cases the critical behaviour of the model is the same as that of the branching annihilating random walk with $N\geq 2$ species both with and without hard-core interaction. We show that certain static characteristics of the so-called natural absorbing states develop power law singularities which signal the approach of the critical point. These results are also explained using random walk arguments. In addition to that we show that when dynamics of our model is considered as a minimum finding procedure, it has the best efficiency very close to the critical point.Comment: 6 page

When challenges hinder: An investigation of buyer-imposed stressors on supplier flexibility

Working with buyers may drive business growth but can also induce supplier stress. Drawing on Job Demands–Resources (JD-R) theory, this study explored how buyer-imposed work stressors affect supplier flexibility. Employing a scenario-based experiment involving 338 managers, we found that the imposition of challenge stressors increases supplier flexibility when hindrance stressors are low. Conversely, when hindrance stressors are high, imposing challenge stressors reduces supplier flexibility. We also found that supplier bricolage negatively moderates the relationship between buyer-imposed challenge stressors and supplier flexibility. Specifically, we confirmed that suppliers with higher bricolage are less willing to provide flexibility in response to challenge stressors. For practitioners, our study not only identified the type of work stressors they should impose on suppliers to boost flexibility but also highlighted bricolage as an important moderating factor

Pushmepullyou: An efficient micro-swimmer

The swimming of a pair of spherical bladders that change their volumes and mutual distance is efficient at low Reynolds numbers and is superior to other models of artificial swimmers. The change of shape resembles the wriggling motion known as {\it metaboly} of certain protozoa.Comment: Minor rephrasing and changes in style; short explanations adde

Effectiveness of cognitive therapy on reducing irrational beliefs of 12-14 Year old adolescents and 18-20 year old adolescents

This study seeks to see whether there is a significant difference in the extent to which REBT reduces irrational beliefs between the two experimental groups: 12-14 year old adolescents and 18-20 year old adolescents? An experimental pre-test and post-test design was used in this research. The sample consisted of 32 Iranian female adolescents living in Kuala Lumpur. They were assigned in 4 groups randomly: one 12-14 year old group, one18-20 year old group; and 2 control groups. Participants took part in 10 Cognitive Therapy sessions. Results show that the treatment has been effective in both groups, but it has been more effective in the 12-14 year old group. Based on this study, the researcher recommends providing REBT psycho-educational programs in educational settings for adolescents who live in foreign countries. Also, it is recommended to integrate cognitive programming as part of classroom curriculum

Coherent Hydrodynamic Coupling for Stochastic Swimmers

A recently developed theory of stochastic swimming is used to study the notion of coherence in active systems that couple via hydrodynamic interactions. It is shown that correlations between various modes of deformation in stochastic systems play the same role as the relative internal phase in deterministic systems. An example is presented where a simple swimmer can use these correlations to hunt a non-swimmer by forming a hydrodynamic bound state of tunable velocity and equilibrium separation. These results highlight the significance of coherence in the collective behavior of nano-scale stochastic swimmers.Comment: 6 pages, 3 figure