Carbon monolith: Preparation,characterization and application as microextraction fiber

A carbon monolith was synthesized via a polymerization–carbonization method, styrene and divinylbenzene being adopted as precursors and dodecanol as a porogen during polymerization. The resultant monolith had bimodal porous substructure, narrowly distributed nano skeleton pores and uniform textural pores or throughpores. The carbon monolith was directly used as an extracting fiber, taking place of the coated silica fibers in commercially available solid-phase microextraction device, for the extraction of phenols followed by gas chromatography–mass spectrometry. Under the studied conditions, the calibration curves were linear from 0.5 to 50 ng mL⁻¹ for phenol, o-nitrophenol, 2,4-dichlorophenol and p-chlorophenol. The limits of detection were between 0.04 and 0.43 ng mL⁻¹. The recoveries of the phenols spiked in real water samples at 10 ng mL⁻¹ were between 85% and 98% with the relative standard deviations below 10%. Compared with the commercial coated ones (e.g. PDMS, CW/DVB and DVB/CAR/PDMS), the carbon monolith-based fiber had advantages of faster extraction equilibrium and higher extraction capacity due to the superior pore connectivity and pore openness resulting from its bimodal porous substructure.     

Characterization of simple K 4-groups

In this paper, we prove that a group G is isomorphic to M, where M is a simple K ₄-group, if and only if the following hold: (1) |G| = |M|, (2) nse(G) = nse(M).      

A market approach to decentralized control of a manufacturing cell

Based on a fictitious market model, a decentralized approach is presented for the workstation scheduling in a CNC workshop. A multi-agent framework is proposed, where job agents and resource agents act as buyers and sellers of resource in the virtual market. With cost and benefit calculation of these agent activities, which reflects the state of the production environment, various, and often conflicting goals and interests influencing the scheduling process in practice can be balanced through a unified instrument offered by the markets. The paper first introduces a heuristic procedure that makes scheduling reservations in a periodic manner. A multi-agent framework is then introduced, in which job agents and resource agents seek appropriate job–workstation matches through bidding in the construction of the above periodic “micro-schedules”. A pricing policy is proposed for the price-directed coordination of agent activities in this. Simulation results demonstrate the feasibility of the proposed approach and give some insights on the effects of some decision making parameters. Future work will be focused on the designing of some more sophisticated coordination mechanism and its deployment.     

Symplectic geometry and geometric quantization on supermanifold withU numbers

The usual theory of supermanifold is extended to the case that contains (anti)commuting variable pairs with oppositeU numbers. The symplectic geometry and geometric quantization on such a special manifold are discussed in detail. As applications, the BRST system with finite dimensional first class constraints and bosonic strings are investigated systematically.     

Synthesis of PrBa2Cu4O8 by Solution Method under Ambient Oxygen Pressure

A highly homogeneous and nearly monophasic PrBa₂Cu₄O₈ compound has been synthesized at 1 atm of oxygen via a route employing polymeric ethylenediamine/citric acid precursors. The PrBa₂Cu₄O₈ compound with a trace amount of BaCuO₂ was synthesized for the first time by sintering the pellets at the temperature of 875 °C under ambient oxygen pressure. The temperature coefficient of the resistivity is positive below 190 K while above 190 K is negative. The superconducting transition was not detected down to 4.2 K. Samples were characterized by X-ray diffraction, scanning electron microscopy, thermal analysis, and transport and magnetic measurements.