Current air quality analytics and monitoring: A review

This review summarizes the different tools and concepts that are commonly applied in air quality monitoring. The monitoring of atmosphere is extremely important as the air quality is an important problem for large communities. Main requirements for analytical devices used for monitoring include a long period of autonomic operation and portability. These instruments, however, are often characterized by poor analytical performance. Monitoring networks are the most common tools used for monitoring, so large-scale monitoring programmes are summarized here. Biomonitoring, as a cheap and convenient alternative to traditional sample collection, is becoming more and more popular, although its main drawback is the lack of standard procedures. Telemonitoring is another approach to air monitoring, which offers some interesting opportunities, such as ease of coverage of large or remote areas, constituting a complementary approach to traditional strategies; however, it requires huge costs.     

3D-TOFSIMS characterization of black spots in polymer light emitting diodes

The occurrence and formation of black spots areas in PolyLED devices has been studied by time-of-flight SIMS (TOFSIMS). The composition, shape and position of the black spots is visualised by three-dimensional (3D)-TOFSIMS depth-profiling. It has been established that the formation of non-emissive spots is due to the growth of aluminium oxide clusters at the AlBa/polymer interface. Electron injection in the black spots is lost by the resulting local increase of the resistivity of the cathode.     

硅光电负阻器件的构成原理与分类

将三端负阻器件与硅光电探测器相结合 ,通过新的构思成功地提出并构成了一类新型光电器件——硅光电负阻器件。文中报道了该器件构成的一般性原理 ,以及依据此构成原理确定的分类方法     

Negative luminescence in semiconductors: a retrospective view

Twenty-five years ago, we introduced the phenomenon of negative luminescence (NL) into semiconductor physics. This paper provides an overview of work conducted to develop this fundamental concept. Initially, we consider the first-principle approach to radiation interaction with basic matter and the major properties of NL. Then we describe the problems of NL direct measurements in homogeneous materials and structures. Finally, we emphasize the use of NL approach in applications involving devices for infrared (IR) wavelength (3–12 μm) high-temperature (300–400 K) optoelectronics. Our subjects will include NL IR emitting diodes, radiative coolers, IR dynamic scene simulators, light up-conversion devices, and the Stealth effect in IR.     

White and Red Organic Light Emitting Materials

Derivatives of 2,3-(1,4-dialkoxyaceno)norbornadiene underwent ring-opening metathesis polymerization (ROMP) upon the catalysis of a ruthenium complex to afford the corresponding polymers. The polymeric materials containing anthracene chromophores emit white electro-luminescence, which can be fabricated into light-emitting diodes (LED). The broad emission band is composed of a blue emission from anthracene and a red emission from aggregates. A single layer device, ITO/polymer/Ca/Al, can be turned on at 7V and exhibits maximum intensity 427 cd/m2 at 15 V. A double layer device, ITO/polymer/TPBI/Mg:Ag (TPBI = (2,2′,2"-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)) displayed blue light with turn-on voltage 6 V and maximal intensity 930 cd/m2 at 15 V.Derivatives of bisindolylmaleimide were found to form amorphous solid films which exhibit intensive red luminescence. The property of forming glasses can be ascribed to the nonplanar geometry of these molecules. LED devices were fabricated by a layer of pure dye sandwiched between two charge transporting films. The yellow emission spectrum of the devices utilizing Alq (tris(8-hydoxyquinolinato)aluminum) contains a green component from Alq. Pure red emissions can be achieved by replacing Alq with TPBI. Typical devices can be turned on at ～3 V with maximal intensity 2000 cd/m2. White color devices are under current investigation, in which the green Alq layer is replaced by its blue derivative (bis(2-methyl-8-hydoxyquinolinato)(phenolato)aluminum).     

噪声测量作为筛选光电耦合器件的一种方法

本文针对目前用于光电耦合器件筛选方法的不足，提出了用测量耦合器件噪声功率谱的方法来筛选掉噪声值大的器件，给出一批光电耦合器件的测量统计结果及在不同工作点时的噪声功率谱，并给出相应的筛选标准，实验结果表明，这种方法是有效、可行的。     

Electronic properties of model quantum-dot structures in zero and finite magnetic fields

We have computed electronic structures and total energies of circularly confined two-dimensional quantum dots and their lateral dimers in zero and finite uniform external magnetic fields using different theoretical schemes: the spin-density-functional theory (SDFT), the current-and-spin-density-functional theory (CSDFT), and the variational quantum Monte Carlo (VMC) method. The SDFT and CSDFT calculations employ a recently-developed, symmetry-unrestricted real-space algorithm allowing solutions which break the spin symmetry. Results obtained for a six-electron dot in the weak confinement limit and in zero magnetic field as well as in a moderate confinement and in finite magnetic fields enable us to draw conclusions about the reliability of the more approximative SDFT and CSDFT schemes in comparison with the VMC method. The same is true for results obtained for the two-electron quantum dot dimer as a function of inter-dot distance. The structure and role of the symmetry-breaking solutions appearing in the SDFT and CSDFT calculations for the above systems are discussed. Received 16 October 2001 and Received in final form 17 January 2002     

Characteristics of transmission of electrons in a quantum wire tangentially attached to a superconductor ring threaded by magnetic flux

We present numerical investigations of the transmission properties of electrons in a normal quantum wire tangentially attached to a superconductor ring threaded by magnetic flux. A point scatterer with a δ -function potential is placed at node to model scattering effect. We find that the transmission characteristics of electrons in this structure strongly depend on the normal or superconducting state of the ring. The transmission probability as a function of the energy of incident electrons, in the case of a superconductor ring threaded by one quantum magnetic flux, emerges one deep dip, imposed upon the first broad bump in spectrum. This intrinsic conductance dip originates from the superconductor state of the ring. When increasing the magnetic flux from one quantum magnetic flux to two, the spectrum shifts toward higher energy region in the whole. This conductance dip accordingly shifts and appears in the second bump. In the presence of a point-scatterer at the node, the spectrum is substantially modified. Based on the condition of the formation of the standing wave functions in the ring and the broken of the time-reserve symmetry of Schr?dinger equation after switching magnetic flux, the characteristics of transmission of electrons in this structure can be well understood. Received 6 November 2001     

Radiation‐induced migration of additives in PVC‐based biomedical disposable devices. Part 1. Surface morphology by AFM and SEM/XEDS

Two different types of plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices—extruded and injection moulded—were studied in the non‐sterilized condition and after 25 and 50 kGy of beta irradiation. The polymer surfaces were analysed by scanning electron microscopy (SEM) equipped with an x‐ray energy‐dispersive spectroscopy (XEDS) and by atomic force microscopy (AFM). The inner surface of two parts of a venous line showed a different morphology according to their original formulation (for extrusion or injection moulding process) and reacted differently on sterilization with beta irradiation. Moulded parts were affected only slightly by the radiation step, whereas the variations were bigger for the extruded parts. In order to gain the best performances for the medical devices studied, the utmost care must be taken in the sterilization step, which should be optimized as well as the other steps of the manufacturing process. Copyright © 2003 John Wiley & Sons, Ltd.