2,114 research outputs found
On the Design of Secure Full-Duplex Multiuser Systems under User Grouping Method
Consider a full-duplex (FD) multiuser system where an FD base station (BS) is
designed to simultaneously serve both downlink users and uplink users in the
presence of half-duplex eavesdroppers (Eves). Our problem is to maximize the
minimum secrecy rate (SR) among all legitimate users by proposing a novel user
grouping method, where information signals at the FD-BS are accompanied with
artificial noise to degrade the Eves' channel. The SR problem has a highly
nonconcave and nonsmooth objective, subject to nonconvex constraints due to
coupling between the optimization variables. Nevertheless, we develop a
path-following low-complexity algorithm, which invokes only a simple convex
program of moderate dimensions at each iteration. We show that our
path-following algorithm guarantees convergence at least to a local optima. The
numerical results demonstrate the merit of our proposed approach compared to
existing well-known ones, i.e., conventional FD and nonorthogonal multiple
access.Comment: 6 pages, 3 figure
Non-linear Microwave Surface Impedance of Epitaxial HTS Thin Films in Low DC Magnetic Fields
We have carried out non-linear microwave (8 GHz) surface impedance
measurements of three YBaCuO thin films in dc magnetic fields
(parallel to c axis) up to 12 mT using a coplanar resonator technique. In zero
dc field the three films, deposited by the same method, show a spread of
low-power residual surface resistance, and penetration depth,
(T=15 K) within a factor of 1.9. However, they exhibit dramatically
different microwave field, dependences of the surface resistance,
, but universal dependence. Application of a dc field was
found to affect not only absolute values of and , but the functional
dependences and as well. For some of the samples
the dc field was found to decrease below its zero-field low-power value.Comment: 4 pages, 4 figures. To be published in IEEE Trans. Appl. Supercond.,
June 199
Solar Flare Intermittency and the Earth's Temperature Anomalies
We argue that earth's short-term temperature anomalies and the solar flare
intermittency are linked. The analysis is based upon the study of the scaling
of both the spreading and the entropy of the diffusion generated by the
fluctuations of the temperature time series. The joint use of these two methods
evidences the presence of a L\'{e}vy component in the temporal persistence of
the temperature data sets that corresponds to the one that would be induced by
the solar flare intermittency. The mean monthly temperature datasets cover the
period from 1856 to 2002.Comment: 4 pages, 5 figure
Identification of Klebsiella pneumoniae in microwavable chicken curries using 16s rRNA analysis
Microwave heating technology is widely used in food catering and domestic households. Nonuniformity of microwave temperature distribution causes the formation of hot and cold spots in heated product has led to the survival of foodborne pathogens which may later cause food borne diseases. It is the aim of this study to determine the effect of different microwave heating on the microbiological quality of microwavable frozen chicken curries. Nine commercialised frozen chicken curries were thawed overnight in the chiller (< 4°C) and exposed to different microwave power levels and times (270 W at 60 s; 950 W at 150 s and 300 s). 25 g of chicken curry were homogenised, serial diluted and enumerated aseptically. Total Aerobic Count (TAC), Total Coliform Count (TCC), Escherichia coli count and Salmonella count were carried out and no microorganisms were detected. Enterobacteriaceae were found in the food samples after enrichment process. Polymerase Chain Reaction (PCR) amplification and 16S ribosomal ribonucleic acid (rRNA) sequencing were carried out. Results of 16S rRNA sequence analysis indicated that two gram-negative isolates after enrichment were identified as Klebsiella pneumoniae
Reaction sintering of porous shape-memory titanium-nickelide-based alloys
The problems of reaction sintering of porous shape-memory Ti−Ni-based alloys are examined. An analysis of the structure and parameters of shape-memory materials produced with the use of different reaction sintering modes is performed. The temperature and time intervals are determined over which liquid-phase sintering points responsible for a qualitative change in the TiNi phase of the reaction-sintered Ti−Ni system are observed. The morphological structure and properties of the porous materials are investigated. Models for interactions between phases and phase transformations in the sintered alloys are built. It has been found that changes in the deformation parameters of the porous titanium nickelide-based alloys correlate with an increase in the volume fraction of the TiNi phase and with its wholeness as the sintering time is increased
Variation of cultivated mungbean and wild vigna as revealed by random amplified polymorphic DNA markers
The genetic variation of nine varieties of cultivated mungbean (Vigna radiata) and three local populations of
wild Vigna (V. trinervia) were evaluated in this study using RAPD markers. A total of 65 scorable DNA fragments ranging in size from 173-1,500 bp were obtained from the PCR amplification usingfive RAPD primers of which 95.38% were polymorphic. Cluster analysis revealed two major groups in which the first group consists of the nine varieties ofV. radiata, while the second group includes the three populations ofV. trinervia. This information is useful for plant breeders to make informed decisions in an effort to devise breeding or crossbreeding programmes for the development of the crop
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