Detection H2S mixed with natural gas using hollow-core photonic bandgap fiber

An optical fiber gas sensor using hollow-core photonic bandgap fiber as a gas cell is proposed to detect H₂S mixed with natural gas. This sensor is advantageous for eliminating instability of light source, impact of thermal zero drift, and zero shift of photoelectric device. The gas sensing probe of configuration is using two shorter pieces of hollow-core photonic bandgap fiber (HC-PBF) with the same overall length instead of one long piece of HC-PBF to improve the system response. The experimental dates indicate that a minimum detectivity of 10 ppm for the system configuration was estimated.     

Digital modeling and control of multiple time-delayed distributed power grid

Distributed power grid (DPG) control systems are so highly interconnected that the effects of local disturbances as well as transmission time delays can be amplified as they propagate through a complex network of transmission lines. These effects deteriorate control performance and could possibly destabilize the overall system. In this paper, a new approximated discretization method and digital design for DPG control systems with multiple state, input and output delays as well as a generalized bilinear transformation method are presented. Based on a procedure for the generation of impulse response data, the multiple fractional/integer time-delayed continuous-time system is transformed to a discrete-time model with multiple integer time delays. To implement the digital modeling, the singular value decomposition (SVD) of a Hankel matrix together with an energy loss level is employed to obtain an extended discrete-time state space model. Then, the extended discrete-time state space model of the DPG control system is reformulated as an integer time-delayed discrete-time system by computing its observable canonical form. The proposed method can closely approximate the step response of the original continuous time-delayed DPG control system by choosing various energy loss levels. For completeness, an optimal digital controller design for the DPG control system and a generalized bilinear transformation method with a tunable parameter are also provided, which can re-transform the integer time-delayed discrete-time model to its continuous-time model. Illustrative examples are given to demonstrate the effectiveness of the developed method.     

N-Doped, porous TiO2 with rutile phase and visible light sensitive photocatalytic activity

Nitrogen-doped, porous rutile has been prepared by hydrothermal reaction of TiN in nitric acid, with the nitrogen atoms present in the interstitial sites and in the form of adsorbed nitrate ions. The N-rutile powder exhibits outstanding photocatalytic activity toward degradation of adsorbed methylene blue under visible light irradiation.     

A design of novel type superconducting magnet for super—high field functional magnetic resonance imaging by using the harmonic analysis method of magnetic vector potentials

The approach of expanding the magnetic scalar potential in a series of Legendre polynomials is suitable for designing a conventional superconducting magnetic resonance imaging magnet of distributed solenoidal configuration. Whereas the approach of expanding the magnetic vector potential in associated Legendre harmonics is suitable for designing a single-solenoid magnet that has multiple tiers, in which each tier may have multiple layers with different winding lengths. A set of three equations to suppress some of the lowest higher-order harmonics is found. As an example, a 4T single-solenoid magnetic resonance imaging magnet with 4×6 layers of superconducting wires is designed. The degree of homogeneity in the 0.5m diameter sphere volume is better than 5.8 ppm. The same degree of homogeneity is retained after optimal integralization of turns in each correction layer. The ratio B_m/B₀ in the single-solenoid magnet is 30% lower than that in the conventional six-solenoid magnet. This tolerates higher rated superconducting current in the coil. The Lorentz force of the coil in the single-solenoid system is also much lower than in the six-solenoid system. This novel type of magnet possesses significant advantage over conventional magnets, especially when used as a super-high field functional magnetic resonance imaging magnet.     

Chalcogen-Containing Manganese Carbonyl Clusters: Synthesis and Structural Transformations

Recently, we have developed several synthetic routes to the new classes of chalcogen-containing manganese carbonyl clusters, and the interesting structural transformations and reactivity of the resultant clusters have been investigated as well. In this short review, the syntheses and bonding modes of the sulfur, selenium, and tellurium-containing manganese carbonyl complexes reported by our laboratory will be presented, and the cluster growth and transformation will be systematically compared and discussed.     

高乌头根中新的二萜生物碱

从高乌头根中分离得到3个新的冉乌头型的C₁₈-二萜生物碱高乌宁己(1)、高乌宁庚(3)、高乌宁辛(5)和一个新的牛扁碱型C₁₉-二萜生物碱高乌宁壬(7). 它们的结构通过IR, ¹H NMR, ¹³C NMR, MS予以确证.     

Synthesis and spectroscopic properties of finite Ph2N-containing oligo(arylenevinylene) derivatives that emit blue to red fluorescence

[structure: see text] A series of oligo(phenylenevinylene) (OPV) derivatives with finite conjugation units were prepared in short steps from few building blocks. The central and terminal aryl groups of these OPV dyes contain cyano and Ph(2)N substituents, respectively, which affect color of fluorescence. The wavelength ranges from 472 nm (blue) to 614 nm (red) depending on the position of the cyano group.     

New C(19)-diterpenoid alkaloids from the roots of Delphinium potaninii var. jiufengshanense

From the roots of Delphinium potaninii var. jiufengshanense, two new lycoctonine-type C(19)-diterpenoid alkaloids called jiufengdine (1) and jiufengtine (4) have been isolated. The structures of the new alkaloids (1, 4) were established by 1D and 2D NMR spectra.     

Self-assembly of a pi-electronic amphiphile consisting of a zinc porphyrin-fullerene dyad: formation of micro-vesicles with a high stability

An amphiphilic zinc porphyrin-fullerene dyad appended with triethyleneglycol chains in aqueous media forms uniformly-sized multilamellar vesicles with a mean diameter of 100 nm that are thermally stable and robust against membrane lysis with surfactants.