Studies of chemomechanical gels and collective behavior in chemical systems

The synthesis, structure and properties of stimuli responsive gels are reviewed. A flow through reactor is constructed by attaching a secondary chamber to the output of a continuously stirred tank reactor (CSTR). The dynamical behavior of the primary and secondary chambers is characterized by carrying out the bromate-sulfite-ferrocyanide reaction in the reactors. The dynamical behavior of the secondary chamber was found to mimic that of the primary chamber. In addition, the secondary chamber offers spatially homogeneous and non-stirred pH oscillations for chemomechanical oscillators and walkers. Chemomechanical oscillators are obtained by placing poly(NIPAAm-co-MAAc) gel rods of diameters less than 530 mum into the secondary chamber of the flow through reactor. The swelling ratio of the gel rods during each oscillation cycle is dependent on the rod diameter. Gel rods of smaller diameters exhibited larger swelling ratios. The linear swelling ratio of a 50 mum diameter rod is 80% and close to the equilibrium swelling ratio. Buckling is observed for gel rods with large swelling ratios. A chemomechanical walker is constructed by adding two capillary legs to a rod comprised of poly(NIPAAm-co-MAAc) gel. The walker moves in a forward-backward-forward pattern, with movement that is highly directional. The translational direction is independent of the surface upon which the walker moves.;Quorum sensing refers to density-dependent gene-transcription regulation phenomena that occurs in certain bacteria colonies. The gene transcription can be turned on at high cell densities and off at low cell densities. A similar transition is observed in locally and globally coupled chemical systems. In a locally coupled system, ferroin-loaded beads are positioned to form a quasicircular monolayer covered by catalyst-free BZ solution. The catalyst BZ solution is composed of 0.10 M NaBr, 0.20 M MA, 0.60 M H2SO4 and varied concentration of NaBrO3. For solutions with NaBrO3 concentrations between 0.24 M and 0.30 M, chemical waves are observed only in groups with a bead number larger than a critical value. A transition from steady state to oscillatory behavior occurs when the size of the group increases. This transition has the features of a dynamical quorum sensing transition. Numerical simulations indicate that the quorum sensing transition is associated with a decrease in the loss of activator to the solution. In a globally coupled system, large populations of ferroin-loaded beads are stirred in a batch reactor at different stirring rates. A transition from steady state to oscillatory behavior is observed when the number density of the beads is increased at high stirring rate. A Kuramoto synchronization transition, where oscillators gradually synchronize as the number density increases, is observed at low stirring rate. Numerical simulations were in accord with both transitions observed experimentally at the corresponding exchange rates

Mobile Conductance in Sparse Networks and Mobility-Connectivity Tradeoff

In this paper, our recently proposed mobile-conductance based analytical framework is extended to the sparse settings, thus offering a unified tool for analyzing information spreading in mobile networks. A penalty factor is identified for information spreading in sparse networks as compared to the connected scenario, which is then intuitively interpreted and verified by simulations. With the analytical results obtained, the mobility-connectivity tradeoff is quantitatively analyzed to determine how much mobility may be exploited to make up for network connectivity deficiency.Comment: Accepted to ISIT 201

Outage Probability of Dual-Hop Multiple Antenna AF Relaying Systems with Interference

This paper presents an analytical investigation on the outage performance of dual-hop multiple antenna amplify-and-forward relaying systems in the presence of interference. For both the fixed-gain and variable-gain relaying schemes, exact analytical expressions for the outage probability of the systems are derived. Moreover, simple outage probability approximations at the high signal to noise ratio regime are provided, and the diversity order achieved by the systems are characterized. Our results suggest that variable-gain relaying systems always outperform the corresponding fixed-gain relaying systems. In addition, the fixed-gain relaying schemes only achieve diversity order of one, while the achievable diversity order of the variable-gain relaying scheme depends on the location of the multiple antennas.Comment: Accepted to appear in IEEE Transactions on Communication

Large area growth and electrical properties of p-type WSe2 atomic layers.

Transition metal dichacogenides represent a unique class of two-dimensional layered materials that can be exfoliated into single or few atomic layers. Tungsten diselenide (WSe(2)) is one typical example with p-type semiconductor characteristics. Bulk WSe(2) has an indirect band gap (∼ 1.2 eV), which transits into a direct band gap (∼ 1.65 eV) in monolayers. Monolayer WSe(2), therefore, is of considerable interest as a new electronic material for functional electronics and optoelectronics. However, the controllable synthesis of large-area WSe(2) atomic layers remains a challenge. The studies on WSe(2) are largely limited by relatively small lateral size of exfoliated flakes and poor yield, which has significantly restricted the large-scale applications of the WSe(2) atomic layers. Here, we report a systematic study of chemical vapor deposition approach for large area growth of atomically thin WSe(2) film with the lateral dimensions up to ∼ 1 cm(2). Microphotoluminescence mapping indicates distinct layer dependent efficiency. The monolayer area exhibits much stronger light emission than bilayer or multilayers, consistent with the expected transition to direct band gap in the monolayer limit. The transmission electron microscopy studies demonstrate excellent crystalline quality of the atomically thin WSe(2). Electrical transport studies further show that the p-type WSe(2) field-effect transistors exhibit excellent electronic characteristics with effective hole carrier mobility up to 100 cm(2) V(-1) s(-1) for monolayer and up to 350 cm(2) V(-1) s(-1) for few-layer materials at room temperature, comparable or well above that of previously reported mobility values for the synthetic WSe(2) and comparable to the best exfoliated materials

Optimal integration of mobile battery energy storage in distribution system with renewables

published_or_final_versio

MIMO Precoding Design with QoS and Per-Antenna Power Constraints

Precoding design for the downlink of multiuser multiple-input multiple-output (MU-MIMO) systems is a fundamental problem. In this paper, we aim to maximize the weighted sum rate (WSR) while considering both quality-of-service (QoS) constraints of each user and per-antenna power constraints (PAPCs) in the downlink MU-MIMO system. To solve the problem, we reformulate the original problem to an equivalent problem by using the well-known weighted minimal mean square error (WMMSE) framework, which can be tackled by iteratively solving three subproblems. Since the precoding matrices are coupled among the QoS constraints and PAPCs, we adopt alternating direction method of multipliers (ADMM) to obtain a distributed solution. Simulation results validate the effectiveness of the proposed algorithm