Capital structure and the firm under uncertainty

This paper examines the interplay between the real and financial decisions of the competitive firm `a la Sandmo. Besides output price uncertainty, the firm faces additional sources of risk which are aggregated into an additive background risk. We show that the firm always chooses its optimal debt-equity ratio to minimize the weighted average cost of capital, irrespective of the risk attitude of the firm and the incidence of the multiple sources of uncertainty. Even though the introduction of the background risk affects neither the optimal debt-equity ratio nor the marginal rate of technical substitution, it does have an adverse effect on the output level of the firm. Furthermore, if capital is a normal input, the presence of the background risk induces the firm to acquire less capital by issuing less debt and equity. --Background risk,Capital structure,Price uncertainty

Sum Rate and Fairness Analysis for the MU-MIMO Downlink under PSK Signalling: Interference Suppression vs Exploitation

In this paper, we analyze the sum rate performance of multi-user multiple-input multiple-output (MU-MIMO) systems, with a finite constellation phase-shift keying (PSK) input alphabet. We analytically calculate and compare the achievable sum rate in three downlink transmission scenarios: 1) without precoding, 2) with zero forcing (ZF) precoding 3) with closed form constructive interference (CI) precoding technique. In light of this, new analytical expressions for the average sum rate are derived in the three cases, and Monte Carlo simulations are provided throughout to validate the analysis. Furthermore, based on the derived expressions, a power allocation scheme that can ensure fairness among the users is also proposed. The results in this work demonstrate that, the CI strictly outperforms the other two schemes, and the performance gap between the considered schemes increases with increase in the MIMO size. In addition, the CI provides higher fairness and the power allocation algorithm proposed in this paper can achieve maximum fairness index

Secure Two-Way Transmission via Wireless-Powered Untrusted Relay and External Jammer

In this paper, we propose a two-way secure communication scheme where two transceivers exchange confidential messages via a wireless powered untrusted amplify-and-forward (AF) relay in the presence of an external jammer. We take into account both friendly jamming (FJ) and Gaussian noise jamming (GNJ) scenarios. Based on the time switching (TS) architecture at the relay, the data transmission is done in three phases. In the first phase, both the energy-starved nodes, the untrustworthy relay and the jammer, are charged by non-information radio frequency (RF) signals from the sources. In the second phase, the two sources send their information signals and concurrently, the jammer transmits artificial noise to confuse the curious relay. Finally, the third phase is dedicated to forward a scaled version of the received signal from the relay to the sources. For the proposed secure transmission schemes, we derive new closed-form lower-bound expressions for the ergodic secrecy sum rate (ESSR) in the high signal-to-noise ratio (SNR) regime. We further analyze the asymptotic ESSR to determine the key parameters; the high SNR slope and the high SNR power offset of the jamming based scenarios. To highlight the performance advantage of the proposed FJ, we also examine the scenario of without jamming (WoJ). Finally, numerical examples and discussions are provided to acquire some engineering insights, and to demonstrate the impacts of different system parameters on the secrecy performance of the considered communication scenarios. The numerical results illustrate that the proposed FJ significantly outperforms the traditional one-way communication and the Constellation rotation approach, as well as our proposed benchmarks, the two-way WoJ and GNJ scenarios.Comment: 14 pages, 6 figures, Submitted to IEEE Transactions on Vehicular Technolog

Predicting The Reliability Of A Repairable System With Competing Failure Modes

The main objective of this project is to analyze the failure data of centrifugal pumps that were provided by a petrochemical plant and to develop a reliability model to predict the failure occurrences for each failure modes

Design and synthesis of 5-HT1A receptor ligands

Serotonin (5-hydroxytryptamine, 5-HT) is a biogenic amine known to function through a number of different 5-HT receptor subtypes. The 5-HT1A receptor subtype is implicated in conditions such as depression and anxiety. There are many examples of selective agonists for this receptor, although selective antagonists have only recently become available. Aryloxyalkylamine ?- adrenergic antagonists, such as pindolol and propranolol, are one of the few classes of ligands that exhibit antagonist activity at 5-HT1A receptors, although they are not selective. This thesis describes the synthesis and biological activity of a series of pindolol and propranolol analogues, with the aim of improving their 5-HT1A receptor affinities and selectivities. Modifications to the terminal amine substituents of these compounds were made and the effect of 7-substitution in the naphthalene ring was explored. These analogues possess high 5-HT1A versus ?-adrenergic receptor selectivities, although few compounds show significant 5-HT1A versus 5-HT1D receptor selectivity. In particular, the 7-CONH2 and 7-CO2Me substituted N,N- ethylbutylaminoethoxynaphthalenes were found to be potent agonists at the 5-HT1A receptor, having IC50 values of 3.3 and 5.2 nM respectively. Substitution of different groups in the 7-position of the naphthalene ring was found to have a profound effect on the 5-HT1A and 5-HT1D receptor affinities. Using the Hansch linear-free energy model, attempts were made to determine the relationships between the physicochemical nature of the substituents and their biological activities at these receptors. A multiple least squares linear regression procedure was used to generate several QSAR models. The models were analysed by statistical procedures to determine their validity and significance. Although the procedure did not yield a valid model for the 5-HT1A receptor affinities, good correlations were obtained for the 5-HT1D receptor affinities