Electronic excitations in the edge-shared relativistic Mott insulator: Na2IrO3

We have investigated the excitation spectra of j(eff) = 1/2 Mott insulator Na2IrO3. Taking into account a relativistic multiplet structure of Ir ions, we have calculated the optical conductivity sigma(omega) and resonant inelastic x-ray scattering (RIXS) spectra, which manifest different features from those of a canonical j(eff) = 1/2 system Sr2IrO4. Distinctly from the two-peak structure in Sr2IrO4, sigma(omega) in Na2IrO3 has a broad single peak dominated by interband transitions from j(eff) = 3/2 to 1/2. RIXS spectra exhibit the spin-orbit (SO) exciton that has a two-peak structure arising from the crystal-field effect, and the magnon peak at energies much lower than in Sr2IrO4. In addition, a small peak near the optical-absorption edge is found in RIXS spectra, originating from the coupling between the electron-hole (e-h) excitation and the SO exciton. Our findings corroborate the validity of the relativistic electronic structure and importance of both itinerant and local features in Na2IrO3.open1122sciescopu

Perceived synchronization of mulsemedia services

Multimedia synchronization involves a temporal relationship between audio and visual media components. The presentation of "in-sync" data streams is essential to achieve a natural impression, as "out-of-sync" effects are often associated with user quality of experience (QoE) decrease. Recently, multi-sensory media (mulsemedia) has been demonstrated to provide a highly immersive experience for its users. Unlike traditional multimedia, mulsemedia consists of other media types (i.e., haptic, olfaction, taste, etc.) in addition to audio and visual content. Therefore, the goal of achieving high quality mulsemedia transmission is to present no or little synchronization errors between the multiple media components. In order to achieve this ideal synchronization, there is a need for comprehensive knowledge of the synchronization requirements at the user interface. This paper presents the results of a subjective study carried out to explore the temporal boundaries within which haptic and air-flow media objects can be successfully synchronized with video media. Results show that skews between sensorial media and multimedia might still give the effect that the mulsemedia sequence is "in-sync" and provide certain constraints under which synchronization errors might be tolerated. The outcomes of the paper are used to provide recommendations for mulsemedia service providers in order for their services to be associated with acceptable user experience levels, e.g. haptic media could be presented with a delay of up to 1 s behind video content, while air-flow media could be released either 5 s ahead of or 3 s behind video content

The Economic Community of West African States : fiscal revenue implications of the prospective economic partnership agreement with the European Union

This paper applies a partial equilibrium model to analyze the fiscal revenue implications of the prospective economic partnership agreement between the Economic Community of West African States (ECOWAS) and the European Union. The authors find that, under standard import price and substitution elasticity assumptions, eliminating tariffs on all imports from the European Union would increase ECOWAS'imports from the European Union by 10.5-11.5 percent for selected ECOWAS countries, namely Cape Verde, Ghana, Nigeria, and Senegal. This increase in imports would be accompanied by a 2.4-5.6 percent decrease in total government revenues, owing mainly to lower fiscal revenues. Tariff revenue losses should represent 1 percent of GDP in Nigeria, 1.7 percent in Ghana, 2 percent in Senegal, and 3.6 percent in Cape Verde. However, the revenue losses may be manageable because of several mitigating factors, in particular the likelihood of product exclusions, the length of the agreement's implementation period, and the scope for reform of exemption regimes. The large country-by-country differences in fiscal revenue loss suggest that domestic tax reforms and fiscal transfers within ECOWAS could be important complements to the agreement's implementation.Free Trade,Economic Theory&Research,Trade Policy,International Trade and Trade Rules,Trade Law

The Low Column Density Lyman-alpha Forest

We develop an analytical method based on the lognormal approximation to compute the column density distribution of the Lyman-alpha forest in the low column density limit. We compute the column density distributions for six different cosmological models and found that the standard, COBE-normalized CDM model cannot fit the observations of the Lyman-alpha forest at z=3. The amplitude of the fluctuations in that model has to be lowered by a factor of almost 3 to match observations. However, the currently viable cosmological models like the lightly tilted COBE-normalized CDM+Lambda model, the CHDM model with 20% neutrinos, and the low-amplitude Standard CDM model are all in agreement with observations, to within the accuracy of our approximation, for the value of the cosmological baryon density at or higher than the old Standard Bing Bang Nucleosynthesis value of 0.0125 for the currently favored value of the ionizing radiation intensity. With the low value for the baryon density inferred by Hogan & Rugers (1996), the models can only marginally match observations.Comment: three postscript figures included, submitted to ApJ

Evolutionary Subnetworks in Complex Systems

Links in a practical network may have different functions, which makes the original network a combination of some functional subnetworks. Here, by a model of coupled oscillators, we investigate how such functional subnetworks are evolved and developed according to the network structure and dynamics. In particular, we study the case of evolutionary clustered networks in which the function of each link (either attractive or repulsive coupling) is updated by the local dynamics. It is found that, during the process of system evolution, the network is gradually stabilized into a particular form in which the attractive (repulsive) subnetwork consists only the intralinks (interlinks). Based on the properties of subnetwork evolution, we also propose a new algorithm for network partition which is distinguished by the convenient operation and fast computing speed.Comment: 4 pages, 4 figure

Large-Scale Structure Shocks at Low and High Redshifts

Cosmological simulations show that, at the present time, a substantial fraction of the gas in the intergalactic medium (IGM) has been shock-heated to T>10^5 K. Here we develop an analytic model to describe the fraction of shocked, moderately overdense gas in the IGM. The model is an extension of the Press & Schechter (1974) description for the mass function of halos: we assume that large-scale structure shocks occur at a fixed overdensity during nonlinear collapse. This in turn allows us to compute the fraction of gas at a given redshift that has been shock-heated to a specified temperature. We show that, if strong shocks occur at turnaround, our model provides a reasonable description of the temperature distribution seen in cosmological simulations at z~0, although it does overestimate the importance of weak shocks. We then apply our model to shocks at high redshifts. We show that, before reionization, the thermal energy of the IGM is dominated by large-scale structure shocks (rather than virialized objects). These shocks can have a variety of effects, including stripping ~10% of the gas from dark matter minihalos, accelerating cosmic rays, and creating a diffuse radiation background from inverse Compton and cooling radiation. This radiation background develops before the first stars form and could have measurable effects on molecular hydrogen formation and the spin temperature of the 21 cm transition of neutral hydrogen. Finally, we show that shock-heating will also be directly detectable by redshifted 21 cm measurements of the neutral IGM in the young universe.Comment: 12 pages, 8 figures, submitted to Ap

Parametric-based distribution duct routing generation using constraint-based design approach

In this paper, we present a generative design approach using constraint-based programming to handle the duct routing for ceiling mounted fan coil systems in buildings. This work utilises and builds on the result from previous approach using case-based reasoning and constraint satisfaction problem to deal with the space configuration of complex design problems for ceiling mounted fan coil systems in buildings. In this work, our approach automates the distribution routing using constraint-based approach. Comparatively to previous work, the system we have developed generates parametric-based models where further interactive modification and interaction is made possible for the end user. This approach has been tested in real case scenario working with our industrial partners

Reputation-based network selection solution in heterogeneous wireless network environments

The significant developments in terms of both mobile computing device (e.g., smartphones, tablets, laptops, etc.) and the wireless communication technologies (e.g., LTE, LTE-Advanced, WiMAX, etc.), lead towards a converged heterogeneous wireless environment. In this context, the user will be facing the problem of selecting from a number of Radio Access Networks that differ in technology, coverage, pricing scheme, bandwidth, latency, etc. In order to provide high quality of service (QoS) to the user in this heterogeneous wireless environment, a network selection solution is required that will efficiently facilitate the vertical handover between different wireless access networks in a seamless manner. In this paper, we propose a reputation-based network selection solution which aims to select the best value network for the user. We propose a network profiling algorithm that used to compute the reputation of each of the available networks based on the joint collaboration of the users within the network. The network with the best reputation value is recommended for selection and handover

Facile and green fabrication of multiple magnetite nano-cores@void@porous shell microspheres for delivery vehicles

Multiple magnetite nano-cores@void@porous shell micro-spheres have been fabricated by using the algae cell wall as the hollow porous shell precursor and the intracellular substances as the reducing agents to form magnetite cores inside the microspheres via hydrothermal reactions. This method not only simplified the fabricating steps and superseded harmful chemical reagents, but also endow the microspheres with a uniform size (~2.5 um), porous shell (~15 nm), multiple magnetite nano-cores (~25 nm) and high void volume ratio (> 70%). The product presents fast magnetic separation and redispersibility as well as pH-switched protein auto-loading (high capacity > 600 mg g-1) and unloading as high performance deliver vehicles