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We consider a full-duplex (FD) multiuser system where an FD base station (BS) is designed to simultaneously serve both downlink (DL) and uplink (UL) users in the presence of half-duplex eavesdroppers (Eves). The problem is to maximize the minimum (max-min) secrecy rate (SR) among all legitimate users, where the information signals at the FD-BS are accompanied with artificial noise to debilitate the Eves' channels. To enhance the max-min SR, a major part of the power budget should be allocated to serve the users with poor channel qualities, such as those far from the FD-BS, undermining the SR for other users, and thus compromising the SR per-user. In addition, the main obstacle in designing an FD system is due to the selfinterference (SI) and co-channel interference (CCI) among users. We therefore propose an alternative solution, where the FD-BS uses a fraction of the time block to serve near DL users and far UL users, and the remaining fractional time to serve other users. The proposed scheme mitigates the harmful effects of SI, CCI and multiuser interference, and provides system robustness. The SR optimization problem has a highly nonconcave and nonsmooth objective, subject to nonconvex constraints. For the case of perfect channel state information (CSI), we develop a low-complexity path-following algorithm, which involves only a simple convex program of moderate dimension at each iteration. We show that our path-following algorithm guarantees convergence at least to a local optimum. Then, we extend the path-following algorithm to the cases of partially known Eves' CSI, where only statistics of CSI for the Eves are known, and worst-case scenario in which Eves can employ a more advanced linear decoder. The merit of our proposed approach is further demonstrated by extensive numerical results.

Nguyen H, Donini A. Larvae of the midge Chironomus riparius possess two distinct mechanisms for ionoregulation in response to ion-poor conditions. Am J Physiol Regul Integr Comp Physiol 299: R762-R773, 2010. First published July 14, 2010 doi:10.1152/ajpregu.00745.2009.-This study examined the role of the anal papillae of the freshwater (FW) chironomid larva Chironomus riparius in ionoregulation under ion-poor conditions. The scanning ion-selective electrode technique (SIET) was utilized to characterize the species, direction, and rates of inorganic ion transport by the anal papillae following acute and long-term exposure to ion-poor water (IPW). The major inorganic ions in the hemolymph of larvae treated as above were measured using standard ion-selective microelectrodes. The anal papillae of C. riparius are sites of net NaCl uptake and H ϩ secretion under FW and IPW conditions and are not likely to be a major contributor of K ϩ exchange. Acute and long-term exposure to IPW increased total net transport of Na ϩ , Cl Ϫ , and H ϩ by the anal papillae, but the mechanisms underlying the increase under the two conditions were different. Acute IPW exposure increased the magnitude of net ion fluxes at sites along the anal papillae, while long-term IPW exposure resulted in increased size of the anal papillae with no change in the magnitude of net ion fluxes. The contribution of the anal papillae to observed alterations of hemolymph ion activities upon exposure to IPW is discussed. Inhibitors of the Na ϩ /H ϩ exchangers (EIPA) and carbonic anhydrase (methazolamide) provide evidence for Na ϩ /H ϩ and Cl Ϫ /HCO 3 Ϫ exchange mechanisms in the anal papillae. This study demonstrates that C. riparius larvae employ two different mechanisms to upregulate the total net transport of ions by the anal papillae, and these mechanisms are at least partially responsible for regulating hemolymph ion activity. chironomid; anal papilla; transepithelial ion transport; inorganic ions; homeostasis HOMEOSTATIC REGULATION OF the ionic and osmotic composition of the blood is critical for survival. Aquatic animals are common inhabitants of dilute freshwater (FW) environments, which are less concentrated than their blood, and thus, are faced with a number of ionic and osmotic challenges in the regulation of salt and water balance (25,31,35,37,41). The paucity of ions in the external medium establishes diffusional ion gradients that favor the osmotic influx of water and passive loss of ions. To counteract the water uptake and dilution of the blood, large amounts of dilute hypotonic urine are produced (6,25,31). To maintain ion balance, ions are actively absorbed from the external medium to replenish the ions lost through excretion and metabolic processes (25,31,44,54,66).FW habitats are variable, and environmental salinity can fluctuate with changes in climate that can lead to dilution through rainfall or concentration through evaporation (43). One of the principal difficulties in assessing the effects of climate change on the environment is the ...

Full-duplex (FD) systems have emerged as an essential enabling technology to further increase the data rate of wireless communication systems. The key idea of FD is to serve multiple users over the same bandwidth with a base station (BS) that can simultaneously transmit and receive the signals. The most challenging issue in designing an FD system is to address both the harmful effects of residual self-interference caused by the transmit-to-receive antennas at the BS as well as the cochannel interference from an uplink user (ULU) to a downlink user (DLU). An efficient solution to these problems is to assign the ULUs/DLUs in different groups/slots, with each user served in multiple groups. Hence, this paper studies the joint design of transmit beamformers, ULUs/DLUs group assignment, and time allocation for each group. The specific aim is to maximize the sum rate under the ULU/DLU minimum throughput constraints. The utility function of interest is a difficult nonconcave problem, and the involved constraints are also nonconvex, and so this is a computationally troublesome problem. To solve this optimization problem, we propose a new path-following algorithm for computational solutions to arrive at least the local optima. Each iteration involves only a simple convex quadratic program. We prove that the proposed algorithm iteratively improves the objective while guaranteeing convergence. Simulation results confirm the fast convergence of the proposed algorithm with substantial performance improvements over existing approaches.Index Terms-Full-duplex radios, full-duplex self-interference, multiuser transmission, nonconvex programming, spectral efficiency, transmit beamforming, user grouping.

This paper investigates the coexistence of non-orthogonal multiple access (NOMA) and full-duplex (FD) to improve both spectral efficiency (SE) and user fairness. In such a scenario, NOMA based on the successive interference cancellation technique is simultaneously applied to both uplink (UL) and downlink (DL) transmissions in an FD system. We consider the problem of jointly optimizing user association (UA) and power control to maximize the overall SE, subject to user-specific quality-ofservice and total transmit power constraints. To be spectrally-efficient, we introduce the tensor model to optimize UL users' decoding order and DL users' clustering, which results in a mixed-integer nonconvex problem. For practically appealing applications, we first relax the binary variables and then propose two low-complexity designs. In the first design, the continuous relaxation problem is solved using the inner convex approximation framework. Next, we additionally introduce the penalty method to further accelerate the performance of the former design. For a benchmark, we develop an optimal solution based on brute-force search (BFS) over all possible cases of UAs. It is demonstrated in numerical results that the proposed algorithms outperform the conventional FD-based schemes and its half-duplex counterpart, as well as yield data rates close to those obtained by BFS-based algorithm. Index TermsFull-duplex radios, non-convex programming, non-orthogonal multiple access, self-interference, spectral efficiency, successive interference cancellation, user clustering.

This paper provides empirical evidence relating to the characteristics of firms adopting ABC compared to those not adopting ABC. The empirical evidence is based on responses received from 120 manufacturing companies. The characteristics explored relate to what are referred to as firm characteristic and business environment variables which are defined as those relating to: cost structure, production complexity, production diversity, firm size and the level of competitive intensity. Five hypotheses are developed from a discussion of the literature relating to adoption issues. The results suggest that there would appear to be significant differences between firms adopting ABC and those not adopting ABC in relation to production complexity, firm size and level of competitive intensity, while there would appear to be no significant differences in relation to the proportion of overhead costs in total manufacturing costs and production diversity.

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Background Although QuantiFERON-TB Gold Plus (QFT-Plus), a new interferon-gamma release assay, has shown good performance in adults, little data is available in children. Methods De-identified data from TB-suspected patients age <18 years with QFT-Plus results, who were admitted or screened at the National Lung Hospital (NLH) in Ha Noi, Vietnam in 2017, were assessed. Logistic regression analyses were performed to determine the characteristics associated with having a positive QFT-Plus result. Sensitivity, both overall and in subgroups of pulmonary TB only (PTB), extra-pulmonary TB (EPTB) only, and both PTB and EPTB were calculated. Results Of 222 children with available QFT-Plus results, 33 were classified as confirmed TB, of whom 18 had QFT-Plus (+) and 15 had QFT-Plus (-). Multiple logistic regression modeling suggested that age, history of TB, and confirmed TB were significantly associated with having a positive QFT-Plus result with an area under the ROC curve of 0.77. QFT-Plus sensitivity in PTB only, EPTB, and both PTB and EPTB patients was 84.2%, 14.3% and 14.3%, respectively. The overall sensitivity of the QFT-Plus assay (regardless PTB or EPTB) in children was 54.5%. Conclusion Although QFT-Plus had a good sensitivity in children having exclusive PTB, it had poor sensitivity in EPTB.