One-step synthesis,characterization and oxidative desulfurization of 12-tungstophosphoric heteropolyanions immobilized on amino functionalized SBA-15

Keggin-type 12-tungstophosphoric [PW₁₂O₄₀]^3? heteropolyanions were successfully immobilized onto mesoporous material surface of SBA-15 functionalized using the (3-aminopropyl)triethoxysilane (APTES) synthesized by one-pot co-condensation method, also called one-step synthesis. The synthesized PW^?-NH₃⁺-SBA-15 catalyst was characterized by XRD, N₂ adsorption–desorption, FT-IR, TGA, SEM, TEM, EDS, XPS methods. The results indicated that ordered hexagonal mesostructure for SBA-15 support was still maintained after being functionalized with amine groups, while the specific surface area of SBA-15 was decreased. The active species of phosphotungstic acid H₃PW₁₂O₄₀ (HPW) retained its Keggin structure of the heteropolyanions on the amine-modified SBA-15. The PW^?–⁺H₃N–SBA–15 catalyst exhibited a high catalytic activity for oxidative desulfurization process of sulfur-containing model fuel. The dibenzothiophene (DBT) conversion of almost 100% was achieved with reaction conditions of 40?mg of catalyst dosage, 2?mL of hydrogen peroxide, 90?°C of reaction temperature, and 120?min of reaction time.     

Epitaxial Strain Control of Relaxor Ferroelectric Phase Evolution

Understanding and ultimately controlling the large electromechanical effects in relaxor ferroelectrics requires intimate knowledge of how the local‐polar order evolves under applied stimuli. Here, the biaxial‐strain‐induced evolution of and correlations between polar structures and properties in epitaxial films of the prototypical relaxor ferroelectric 0.68PbMg_1/3Nb_2/3O₃–0.32PbTiO₃ are investigated. X‐ray diffuse‐scattering studies reveal an evolution from a butterfly‐ to disc‐shaped pattern and an increase in the correlation‐length from ≈8 to ≈25 nm with increasing compressive strain. Molecular‐dynamics simulations reveal the origin of the changes in the diffuse‐scattering patterns and that strain induces polarization rotation and the merging of the polar order. As the magnitude of the strain is increased, relaxor behavior is gradually suppressed but is not fully quenched. Analysis of the dynamic evolution of dipole alignment in the simulations reveals that, while, for most unit‐cell chemistries and configurations, strain drives a tendency toward more ferroelectric‐like order, there are certain unit cells that become more disordered under strain, resulting in stronger competition between ordered and disordered regions and enhanced overall susceptibilities. Ultimately, this implies that deterministic creation of specific local chemical configurations could be an effective way to enhance relaxor performance.     

Dynamic Data Rate and Transmit Power Adjustment in IEEE 802.11 Wireless LANs

In this paper a novel link adaptation algorithm is proposed that is capable of adjusting the transmit power level and the data rate jointly to the radio channel conditions. The proposed method relies solely on link quality information available at the transmitter by employing the reception or non-reception of the acknowledgment frames as a measure of the channel quality with respect to the power level and data rate. The method is fully compatible with the 802.11 wireless LAN standard. In contrast to many other proposals, it neither relies on the RTS/CTS protocol nor requires a feedback channel to transmit link-quality estimates from the receiver to the transmitter. Different strategies for optimizing the data rate and power level are given. These depend on the scenarios considered, the number of active stations, and the service requirements. The two main strategies are either to drive the system towards the highest possible data rate and adjust the rate and power levels accordingly (“high-performance” mode) or to focus on power saving, possibly trading this for other performance criteria such as throughput or delay performance (“low-power” mode). Other special cases, such as power or rate only adaptation, are also discussed. It can be shown that in most cases the best choice for achieving low transfer times, maximizing throughput, and alleviating the hidden terminal problem is to transmit at the highest possible rates and with high power levels. This “high-performance” mode of operation also minimizes the transmission times, which in turn maximizes the time for putting idling components into a sleep mode, thereby minimizing the overall power consumption.     

Directed Assembly of Liquid Metal–Elastomer Conductors for Stretchable and Self-Healing Electronics

Growing interest in soft robotics, stretchable electronics, and electronic skins has created demand for soft, compliant, and stretchable electrodes and interconnects. Here, dielectrophoresis (DEP) is used to assemble, align, and sinter eutectic gallium indium (EGaIn) microdroplets in uncured poly(dimethylsiloxane) (PDMS) to form electrically conducting microwires. There are several noteworthy aspects of this approach. 1) Generally, EGaIn droplets in silicone at loadings approaching 90 wt% remain insulating and form a conductive network only when subjected to sintering. Here, DEP facilitates assembly of EGaIn droplets into conductive microwires at loadings as low as 10 wt%. 2) DEP is done in silicone for the first time, enabling the microwires to be cured in a stretchable matrix. 3) Liquid EGaIn droplets sinter during DEP to form a stretchable metallic microwire that retains its shape after curing the silicone. 4) Use of liquid metal eliminates the issue of compliance mismatch observed in soft polymers with solid fillers. 5) The silicone–EGaIn “ink” can be assembled by DEP within the crevices of severely damaged wires to create stretchable interconnects that heal the damage mechanically and electrically. The DEP process of this unique set of materials is characterized and the interesting attributes enabled by such liquid microwires are demonstrated.     

Fast Four‐Way Parallel Radix Sorting on GPUs

Efficient sorting is a key requirement for many computer science algorithms. Acceleration of existing techniques as well as developing new sorting approaches is crucial for many real‐time graphics scenarios, database systems, and numerical simulations to name just a few. It is one of the most fundamental operations to organize and filter the ever growing massive amounts of data gathered on a daily basis. While optimal sorting models for serial execution on a single processor exist, efficient parallel sorting remains a challenge. In this paper, we present a hardware‐optimized parallel implementation of the radix sort algorithm that results in a significant speed up over existing sorting implementations. We outperform all known General Processing Unit (GPU) based sorting systems by about a factor of two and eliminate restrictions on the sorting key space. This makes our algorithm not only the fastest, but also the first general GPU sorting solution.     

Double Doping of Semiconducting Polymers Using Ion-Exchange with a Dianion

The interactions between counterions and electronic carriers in electrically doped semiconducting polymers are important for delocalization of charge carriers, electronic conductivity, and thermal stability. The introduction of a dianions in semiconducting polymers leads to double doping where there is one counterion for two charge carriers. Double doping minimizes structural distortions, but changes the electrostatic interactions between the carriers and counterions. Polymeric ionic liquids (PIL) with croconate dianions are helpful to investigate the role of the counterion in p-type semiconducting polymers. PILs prevent diffusion of the cation into the semiconducting polymers during ion exchange. The redox-active croconate dianions undergo ion exchange with doped semiconducting polymers depending on their ionization energy. Croconate dianions are found to reduce doped films of poly(3-hexyl thiophene), but undergo ion exchange with a polythiophene with tetraethylene glycol side chains, P(g₄2T-T), that has a lower ionization energy. The croconate dianion maintains crystalline order in P(g₄2T-T) and leads to a lower activation energy for the electrical conductivity than PF₆⁻ counterions. The control of the doping level with croconate allows optimization of the thermoelectric performance of the semiconducting polymer. The thermal stability of the doped films of P(g₄2T-T) is found to depend strongly on the nature of the counterion.     

Spline-based feature curves from point-sampled geometry

Defining sharp features in a 3D model facilitates a better understanding of the surface and aids geometric processing and graphics applications, such as reconstruction, filtering, simplification, reverse engineering, visualization, and non-photo realism. We present a robust method that identifies sharp features in a point-based model by returning a set of smooth spline curves aligned along the edges. Our feature extraction leverages the concepts of robust moving least squares to locally project points to potential features. The algorithm processes these points to construct arc-length parameterized spline curves fit using an iterative refinement method, aligning smooth and continuous curves through the feature points. We demonstrate the benefits of our method with three applications: surface segmentation, surface meshing and point-based compression.     

A secure routing scheme for mobile wireless sensor networks

Frequency-hopping (FH) is a well-known spread-spectrum method of transmitting radio signals by hopping frequency channels along a predefined hopping sequence known to both transmitter and receiver. Although FH is resistant to jamming by external malicious nodes which have no knowledge of the sequence, it is of no effect against attacks by internal compromised nodes which know the sequence. In this article, we propose a secure scheme for creating the hopping sequence for mobile wireless sensor networks. The proposed scheme is based on the idea of a statistical en-route filtering (SEF). SEF exploits collective decision making by multiple detecting nodes in the dense deployment of large sensor networks. We demonstrate the effectiveness of our scheme thorough simulations.     

Completeness of hyper-resolution via the semantics of disjunctive logic programs

We present a proof of completeness of hyper-resolution based on the fixpoint semantics of disjunctive logic programs. This shows that hyper-resolution can be studied from the point of view of logic programming.