How to Compute Modulo Prime-Power Sums

The problem of computing modulo prime-power sums is investigated in distributed source coding as well as computation over Multiple-Access Channel (MAC). We build upon group codes and present a new class of codes called Quasi Group Codes (QGC). A QGC is a subset of a group code. These codes are not closed under the group addition. We investigate some properties of QGC's, and provide a packing and a covering bound. Next, we use these bounds to derived achievable rates for distributed source coding as well as computation over MAC. We show that strict improvements over the previously known schemes can be obtained using QGC's

A New Achievable Rate Region for Multiple-Access Channel with States

The problem of reliable communication over the multiple-access channel (MAC) with states is investigated. We propose a new coding scheme for this problem which uses quasi-group codes (QGC). We derive a new computable single-letter characterization of the achievable rate region. As an example, we investigate the problem of doubly-dirty MAC with modulo-$4$ addition. It is shown that the sum-rate $R_1+R_2=1$ bits per channel use is achievable using the new scheme. Whereas, the natural extension of the Gel'fand-Pinsker scheme, sum-rates greater than $0.32$ are not achievable.Comment: 13 pages, ISIT 201

Flowering, Physiological and Biochemical Responses of Two Echinacea Species to Drought Stress

Drought is one of the most important environmental stressors that limit plant\u27s productivity. To evaluate the effects of drought stress on Echinacea purpurea and Echinacea angustifolia seedlings at the four-leaf stage, an experiment was conducted with four levels of irrigation regimes: 25%, 50%, 75%, and 100% of field capacity (FC) in a CRD based factorial experiment with three replications. Growth indices such as shoot and root dry and fresh weight, were reduced at lower FC in both species, but E. angustifolia showed more sensitivity than E. purpurea. Drought stress significantly affected flower stem length, flower longevity, flower diameter, and flower anthocyanin in both species. In addition, flowering was not observed in E. angustifolia under 50% and 25% FC treatment, but the longest flowering period was recorded in E. purpurea under 75% FC treatment (37 days). In this study, leaf carotenoid and anthocyanin contents increased, while the total chlorophyll content decreased under severe drought stress. A reduction of protein content and antioxidant capacity were observed in both species during severe drought stress. The highest amount of electrolyte leakage, malondialdehyde (MDA), total sugars, and proline was observed in E. angustifolia under 25% FC treatment. Catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) antioxidant enzymes activity increased at severe drought stress. Overall, the results indicate that E. purpurea is more drought tolerant than E. angustifolia and E. purpurea is a good candidate for arid and semi-arid regions with limited water resources

Adaptive control design for a synchronous generator

The operating point of a power system changes to an unknown point with an unknown change in the mechanical input power. In this paper, a nonlinear adaptive controller is designed for excitation system of the generator based on the backstepping control technique, in order to achieve transient stability enhancement, in the presence of uncertainties in mechanical power. The designed controller guarantees the convergence of system states to new desired values corresponding to unknown mechanical power. A power system consisting of a synchronous generator connected to an infinite bus through a double circuit transmission line is used in control design and the simulation studies. Computer simulation verifies the effectiveness and the validity of the proposed control, considering faulted system with a clearance and change in network topology. © 2014, Editura Academiei Romane. All rights reserved

Dual energy X-ray absorptiometry diagnostic discordance between Z scores and T scores in a young Iranian population

Background: Dual-energy X-ray Absorptiometry (DXA) is considered the gold standard for non-invasive measurement of bone mass. T-scores and Z-scores are used to present the results of bone mass. The present study was designed to evaluate the discordance between T-scores and Z-scores calculated at a same level and its relation with age, gender and body mass index (BMI) in a representative sample of normal population. Methods: This cross-sectional study was conducted as a part of a comprehensive survey, Iranian Multicenter Osteoporosis Study (IMOS), designed to assess bone health among healthy adults. Each individual underwent both L1–L4 antero-posterior lumbar spine and hip DXA scan. The difference between the T- and Z-scores measured at each of the four skeletal sites was then calculated. Results: A -1.21 to 1.21 point difference was noted in the Z- and T- scores measured at each site. While the difference between the T- and Z-scores was less than 0.5 SD in most of the cases, the difference was higher than 1 SD in about 5% of the subjects. Conclusion: Standardization of Z-score definition and calculation techniques as well as developing an ethnicity-matched reference population is needed to improve the reliability of DXA-generated Z-scores

Boolean Functions with Biased Inputs: Approximation and Noise Sensitivity

This paper considers the problem of approximating a Boolean function $f$ using another Boolean function from a specified class. Two classes of approximating functions are considered: $k$-juntas, and linear Boolean functions. The $n$ input bits of the function are assumed to be independently drawn from a distribution that may be biased. The quality of approximation is measured by the mismatch probability between $f$ and the approximating function $g$. For each class, the optimal approximation and the associated mismatch probability is characterized in terms of the biased Fourier expansion of $f$. The technique used to analyze the mismatch probability also yields an expression for the noise sensitivity of $f$ in terms of the biased Fourier coefficients, under a general i.i.d. input perturbation model.Comment: 5 pages, 2 figures, To appear in IEEE ISIT 201

Bounds on the Effective-length of Optimal Codes for Interference Channel with Feedback

In this paper, we investigate the necessity of finite blocklength codes in distributed transmission of independent message sets over channels with feedback. Previously, it was shown that finite effective length codes are necessary in distributed transmission and compression of sources. We provide two examples of three user interference channels with feedback where codes with asymptotically large effective lengths are sub-optimal. As a result, we conclude that coded transmission using finite effective length codes is necessary to achieve optimality. We argue that the sub-optimal performance of large effective length codes is due to their inefficiency in preserving the correlation between the inputs to the distributed terminals in the communication system. This correlation is made available by the presence of feedback at the terminals and is used as a means for coordination between the terminals when using finite effective length coding strategies