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In this paper, a high-performance routing protocol with multiple mobile nodes based on reliable active nodes is put forward since network nodes are not involved in the reliability work when the existing OSPF routing protocol forwards the packet, which results in several problems such as a low rate of packet forwarding, the long average delay of end-to-end, high energy consumption of network nodes and short service lifetime of nodes. The hierarchical model of active networks with multiple-mobile nodes was built, in which, reliable active nodes were divided into forwarding nodes and reliable nodes based on the functional requirements of this model, and consideration was given both to the efficiency and reliability of packet transmission. Besides, the energy consumption of network communication was calculated on the basis of this model and the packet transmission power was controlled. A high-performance routing protocol with multiple mobile nodes was designed to estimate the packet transmission delay time, calculate the forwarding moderate index of nodes, and select neighbor nodes in the active network. The simulation results show that this routing communication protocol effectively improves the packet forwarding rate, lowers the total energy consumption, shortens the average delay of end-to-end, and extends the service life of network nodes. &nbsp

There are some problems in the semantic internet of things, such as the limited resources of atomic services provided by physical devices and the dynamic changes of their environment. Based on this, this paper proposes a dynamic service composition method based on QoS in the semantic Internet of things. According to the QoS ontology of adding context, this method dynamically annotates the services in the semantic Internet of things, and dynamically selects and combines the service set to be selected. It can dynamically provide accurate services for service requesters according to service objects and service environment.

A novel aldo-keto reductase Tm1743 characterized from Thermotoga maritima was explored as an effective biocatalyst in chiral alcohol production. Natural Tm1743 catalyzes asymmetric reduction of ethyl 2-oxo-4-phenylbutyrate (EOPB) at high efficiency, but the production of, ethyl (S)-2-hydroxy-4-phenylbutyrate ((S)-EHPB), which is less desirable, is preferred with an enantiomeric excess (ee) value of 76.5%. Thus, altering the enantioselectivity of Tm1743 to obtain the more valuable product (R)-EHPB for angiotensin drug synthesis is highly desired. In this work, we determined the crystal structure of Tm1743 in complex with its cofactor NADP+ at 2.0 Å resolution, and investigated the enantioselectivity of Tm1743 through semi-rational enzyme design. Molecular simulations based on the crystal structure obtained two binding models representing the pro-S and pro-R conformations of EOPB. Saturation mutagenesis studies revealed that Trp21 and Trp86 play important roles in determining the enantioselectivity of Tm1743. The best (R)- and (S)-EHPB preferring Tm1743 mutants, denoted as W21S/W86E and W21L/W118H, were identified; their ee values are 99.4% and 99.6% and the catalytic efficiencies are 0.81 and 0.12 mM−1s−1, respectively. Our work presents an efficient strategy to improve the enantioselectivity of a natural biocatalyst, which will serve as a guide for further exploration of new green catalysts for asymmetric reactions.

Filling mining method is widely used in secondary recovery process of hidden danger resources, so great significance has been attached to figure out the interaction mechanism between backfill and r...

Different photoluminescence (PL) spectra are observed for rf magnetron sputtered polycrystalline Mg0.25Zn0.75O and Mg0.37Zn0.63O films on silicon substrates when excited by different wavelengths. When the excitation wavelength is 280 nm, a UV emission peak at 370 nm and a blue peak at 462 nm are generated for the Mg0.25Zn0.75O film, and those two peaks for the Mg0.37Zn0.63O film shift to 366 nm and 466 nm, respectively. The wavelengths of the PL peaks are related to the excitation wavelength. The stronger peak is obtained in the blue band due to a large number of oxygen vacancies caused by excess Zn and Mg atoms, while the weaker peak is obtained in the ultraviolet band.

ZnO nanorods are fabricated by hydrothermal method on glass substrates that are covered with a ZnO seed layer by the thermal decomposition of zinc acetate. The influences of the thermal decomposition temperature on the structural and the optical properties of the obtained ZnO nanorods are carefully studied by using X-ray diffractometry, scanning electron microscopy and spectrophotometry. It is found that the crystalline quality, head-face dimension, macro stress, and transmissivity are found to be dependent on the thermal decomposition temperature. The 〈002〉c-axis-preferred orientation of the obtained ZnO nanorod is first enhanced and then weakened; the macro tensile stress first decreases and then increases; the average transmissivity first increases and then decreases as thermal decomposition temperature increases. When the thermal decomposition temperature reaches 350 ℃, the c-axis preferred orientation is strongest; the tensile stress is smallest; the average transmissivity in the visible region is maximal for the obtained ZnO nanorod. The surface scattering induced by the head-face dimension is the key mechanism of the average transmissivity of the obtained ZnO nanorod in the visible region.

Ag-doped ZnO nanorods with different morphologies and optical properties are synthesized by hydrothermal method on the DC magnetron-sputtered Al-doped ZnO (AZO) seed layers. The influences of the molar ratio of Ag ions to Zn ions (RAg/Zn) and the AZO seed layer on the structural and optical properties of the Ag-doped ZnO nanorods are carefully studied by using X-ray diffractometry, scanning electron microscopy, spectrophotometry, EDS spectrum, etc. The changes in the microstructure and optical property of Ag-doped ZnO nanorods are closely related to the change in the average head-face dimension induced by Ag doping as RAg/Zn increases, owing to the different relative proportions of Ag ions doped in ZnO nanorods resulting from the different particle sizes and densities of the seed layers. The photoluminescence intensity in the visible region for the ZnO nanorods growing on the 15 min-sputtered AZO is stronger than that of the ZnO nanorods growing on the 10 min-sputtered AZO seed layer at the same RAg/Zn, which results from the increased defects in ZnO. More point defects caused by Ag doping are produced as RAg/Zn increases, resulting in the broadening of PL envelope in the visible region. The microstructure of pure ZnO nanorod is related to the seed layer thickness-related degree of crystallinity and particle size.

Considerable protocol development efforts in recent ATM (Asynchronous Transfer Mode) Forum activities have been focused on the traffic management of available bit rate (ABR) service. It has been shown that ABR service enables persistent, greedy data sources to efficiently utilize ATM network resources with the help of a rate-based flow control mechanism. ATM Forum Traffic Management Specification Version 4.0 document gives a complete description of the end system behavior of the flow control mechanism, but it leaves the details of the switch behavior to be vendor-implementation dependent. For the sake of compatibility and interoperation among flow control mechanisms implemented by vendors, two rate-based mechanisms EPRCA (Enhanced Proportional Rate Control Algorithm) and ERICA (Explicit Rate Indication for Congestion Avoidance) have been recommended in the specification. In this paper, the mechanisms are studied and their performance is analyzed and compared with a material network. Simulation shows that ERICA is significantly better than EPRCA in the performance of steady state and instantaneous state of source end system ACR (Allowed Cell Rate) and buffer queue of bottleneck switch.