Opportunistic Relaying in Time Division Broadcast Protocol with Incremental Relaying

In this paper, we investigate the performance of time division broadcast protocol (TDBC) with incremental relaying (IR) when there are multiple available relays. Opportunistic relaying (OR), i.e., the “best” relay is select for transmission to minimize the system’s outage probability, is proposed. Two OR schemes are presented. The first scheme, termed TDBC-OIR-I, selects the “best” relay from the set of relays that can decode both flows of signal from the two sources successfully. The second one, termed TDBC-OIR-II, selects two “best” relays from two respective sets of relays that can decode successfully each flow of signal. The performance, in terms of outage probability, expected rate (ER), and diversity-multiplexing tradeoff (DMT), of the two schemes are analyzed and compared with two TDBC schemes that have no IR but OR (termed TDBC-OR-I and TDBC-OR-II accordingly) and two other benchmark OR schemes that have no direct link transmission between the two sources

On the homotopy of closed manifolds and finite CW-complexes

We study the finite generation of homotopy groups of closed manifolds and finite CW-complexes by relating it to the cohomology of their fundamental groups. Our main theorems are as follows: when $X$ is a finite CW-complex of dimension $n$ and $\pi_1(X)$ is virtually a Poincar\'e duality group of dimension $\geq n-1$, then $\pi_i(X)$ is not finitely generated for some $i$ unless $X$ is homotopy equivalent to the Eilenberg--MacLane space $K(\pi_1(X),1)$; when $M$ is an $n$-dimensional closed manifold and $\pi_1(M)$ is virtually a Poincar\'e duality group of dimension $\ge n-1$, then for some $i\leq [n/2]$, $\pi_i(M)$ is not finitely generated, unless $M$ itself is an aspherical manifold. These generalize theorems of M. Damian from polycyclic groups to any virtually Poincar\'e duality groups. When $\pi_1(X)$ is not a virtually Poincar\'e duality group, we also obtained similar results. As a by-product we showed that if a group $G$ is of type F and $H^i(G,\mathbb{Z} G)$ is finitely generated for any $i$, then $G$ is a Poincar\'e duality group. This recovers partially a theorem of Farrell

Characterizing Ranked Chinese Syllable-to-Character Mapping Spectrum: A Bridge Between the Spoken and Written Chinese Language

One important aspect of the relationship between spoken and written Chinese is the ranked syllable-to-character mapping spectrum, which is the ranked list of syllables by the number of characters that map to the syllable. Previously, this spectrum is analyzed for more than 400 syllables without distinguishing the four intonations. In the current study, the spectrum with 1280 toned syllables is analyzed by logarithmic function, Beta rank function, and piecewise logarithmic function. Out of the three fitting functions, the two-piece logarithmic function fits the data the best, both by the smallest sum of squared errors (SSE) and by the lowest Akaike information criterion (AIC) value. The Beta rank function is the close second. By sampling from a Poisson distribution whose parameter value is chosen from the observed data, we empirically estimate the $p$-value for testing the two-piece-logarithmic-function being better than the Beta rank function hypothesis, to be 0.16. For practical purposes, the piecewise logarithmic function and the Beta rank function can be considered a tie.Comment: 15 pages, 4 figure

Re-analyzing the economic impact of a global bunker emissions charge

© 2018 Elsevier B.V. Regulating bunker emissions continues to be a challenging task, largely due to the lack of a globally coordinated scheme providing economic and political incentives to potential participating countries. This paper analyses the economic costs and benefits of imposing a global carbon tax on international bunker emissions by employing a computable general equilibrium model approach. Under the assumption of an emissions reduction of 5% below 2000 levels by 2020, we demonstrate that a global bunker emissions charge, on one hand, reduces trade volume and change trade patterns between countries and regions, while on the other hand, accelerates the adoption of energy-saving technologies and reallocates the supply of international transportation services throughout the world. The net economic impact, though negative on average, is modest compared to the benefits obtained from the emissions reduction. If revenues from a bunker emissions charge are properly distributed among countries and regions, the losses to disadvantaged countries are likely to be offset by the benefits to advantaged countries. This finding provides useful insights for policy-makers: a global bunker emissions charge could, in future, be an economically feasible strategy to reduce the increasing bunker emissions through the implementation requires more political effort and wisdom

Economic, social and environmental impacts of fuel subsidies: A revisit of Malaysia

© 2017 Elsevier Ltd Subsidizing energy has been widely used but is economically unfavorable. The Malaysian government has shown strong intention to reduce energy subsidies recently, but face challenges to prepare policy instruments to manage the impact. This study develops a Computable General Equilibrium (CGE) model with breakdown of households by income level to evaluate the potential impacts of removing energy subsidies on the Malaysian economy. It is shown that removing petroleum and gas subsidy would improve economic efficiency and increase GDP up to 0.65%. Budget deficit would be largely reduced after removing the petroleum subsidies, especially when the saved subsidy cost is not budgeted for other expenditure. Households would be worse off in most scenarios due to higher price level, but some compensation policy could make the lowest income group no worse than baseline, without harm the economy. The reduction in carbon emissions ranges 1.84–6.63% in different scenarios. The simulation results suggest Malaysia to completely remove all fuel subsidies and use the saved funding to cut budget deficit or spend on education, health and other service sector. It is also necessary to set a compensation scheme to minimize public resistance and make sure such scheme is affordable

Hydrogenated Si12Au20 cluster as a molecular sensor with high performance for NH3 and NO detection: A first-principle study

Using density functional theory (DFT) calculations, we investigated the adsorption of NH3, NO, CH4, CO2, H2, N2, H2O, and O2 molecules on the (hydrogenated) Si12Au20 cluster with the aim of finding a promising molecular sensor for NH3 and NO detection. The Si12Au20 cluster could be a disposable molecular sensor for NH3 and NO because of its long recovery time (over 3 h). To improve the recovery time, we considered the hydrogenation of Si atoms in the Si12Au20 cluster to reduce the strength of the adsorption of NH3 and NO. The vibrational frequency analysis, molecular dynamics simulations and electronic properties show that the H12Si12Au20 (HSA) structure is highly stable. NH3 and NO are chemisorbed on HSA with moderate adsorption energies and evident charge transfer, while the other molecules are all physiosorbed on HSA. Our results show that the electrical conductivities of HSA will change dramatically due to the adsorption of NH3 and NO molecules. The recovery time of HSA is predicted to be very short at 300 K. To have a comprehensive comparison with the above results, we also considered different coverages of NO or NH3 molecules adsorbed on HSA, and the adsorption of NO and NH3 on the Au32 and Si32 clusters. We found that Au32 and Si32 clusters are not suitable for NO and NH3 detection. We predict that HSA should be a promising gas sensor with high performance for NH3 and NO detection at low coverage for future experimental validation