Overload control in the network domain of LTE/LTE-A based machine type communications

It is expected that the LTE network, which includes the Radio Access Network (RAN) and the Core Network (CN) in 3GPP LTE systems, will be overloaded due to the huge number of Machine-Type Communication (MTC) devices in the near future. Overload in the RAN and CN of the LTE may result in congestion occurrence, resource waste, Quality of Service (QoS) degradation and in the worst-case, it will cause service unavailability. In this paper, we have proposed an adaptive mechanism to manage a large number of MTC devices in both RAN and CN of the LTE network. We use Access Class Barring (ACB) scheme to regulate the MTC traffic according to the congestions level in the RAN and CN. We consider a scenario in which two-priority-based classes of MTC devices are contending for the RAN resources. At first, the overload problem in the RAN is formulated to find the number of allowable contending MTC devices of each class taking into account their required QoS. Then, an active load management policy based on additive increase multiplicative decrease rule is proposed to control the incoming load from multiple cells to the CN. To effectively limit the number of MTC devices in both RAN and CN, in the proposed approach, each Evolved Node B updates the ACB factor upon overload detection in the RAN or CN in an adaptive manner. Simulation results show that the proposed mechanism is able to manage overload in the CN and RAN simultaneously.     

Solid phase extraction of trace amounts of Ag, Cd, Cu, and Zn in environmental samples using magnetic nanoparticles coated by 3-(trimethoxysilyl)-1-propantiol and modified with 2-amino-5-mercapto-1,3,4-thiadiazole and their determination by ICP-OES

A fast, sensitive, and simple method using magnetic nanoparticles (MNPs) coated by 3-(trimethoxysilyl)-1-propantiol and modified with 2-amino-5-mercapto-1,3,4-thiadiazole, as an adsorbent has been successfully developed for extraction, preconcentration, and determination of trace amounts of Ag, Cd, Cu, and Zn from environmental samples. The prepared nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). These magnetic nanoparticles can be easily dispersed in aqueous samples and retrieved by the application of external magnetic field via a piece of permanent magnet. The main factors affecting the extraction efficiency such as pH value, sample volume, eluent concentration and volume, ultrasonication time, and coexisting ions have been investigated and established. Under the optimal conditions, high concentration factors (194, 190, 170, and 182) were achieved for Ag, Cd, Cu, and Zn with relative standard deviations of 5.31%, 4.03%, 3.62%, and 4.20%, respectively. The limits of detection for Ag, Cd, Cu, and Zn were as low as 0.12, 0.12, 0.13 and 0.11 ng mL(-1). The prepared sorbent was applied for preconcentration of trace amounts of Ag, Cd, Cu, and Zn in the various water samples with satisfactory results.     

Organo-catalytic synthesis of oxathians from isocyanides,isothiocyanates, and oxiranes

ABSTRACT

A novel three-component reaction between isocyanides, isothiocyanates, and oxiranes has been developed. An array of substituted oxathianes have been obtained in acceptable to good yields. The reaction product could be modulated using Bu₃P or TBPAc as an organo-catalyst. This work offers an opportunity for the further implementation of isocyanides in library design.     

Facile Carbothermal Reduction Synthesis of ZrB2 Nanoparticles: The Effect of Starting Precursors

Zirconium diboride (ZrB₂) ceramic nanoparticles were synthesized by using zirconium (IV) complexes as new precursors. The citrate sol–gel process, which included the mixing of ions at the atomic scale, affected hydrolysis reactions and finally led to the formation of the pure phase of the sample. Results showed that the different sizes of ZrB₂ nanocrystals were produced by adjusting four potential chelating agents of bi- and tetra-dentate (N₂O₂ donor set) ligands by the sol-gel process during carbothermal reduction. The samples were characterized by thermal gravimetric analysis (TGA), X-ray diffraction, fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results obtained from microscopic observations indicated that pure and homogeneous ZrB₂ nanostructures have been formed by using 2-hydroxyacetophenone (hap).