Abstract-Recent studies on radio reality provided strong evidence that radio links between low-power sensor devices are extremely unreliable. In this paper, we study how to improve energy efficiency for reliable communication using such unreliable links. We identify an optimal bound on energy efficiency for reliable communication, and propose a new communication model in the link layer that asymptotically approaches this bound. This new model indicates a better path metric compared to previous path metrics, and we validate this by establishing a routing infrastructure based on this metric, which indeed achieves a higher energy efficiency compared to other stateof-the-art approaches. We present results from a systematic analysis, simulations and prototype experiments based on the MicaZ platform. The results give us fundamental insights on communication efficiency over unreliable links.
A kind of novel superabsorbent hydrogel with high swelling ratio property that could be used for the development of water absorbing resin, soil water retention agent, and chemical sand-fixing material was synthesized in this study. The hydrogels were prepared by the crosslinking reaction of polysuccinimide (PSI). The relationships between swelling ratio and volume of solvent as well as the concentration of crosslinking agent were investigated in detail. Several composites, such as starch, carrageenan, and polyacrylamide, were added into hydrogels to enhance the swelling ratio. It was found that the swelling ratio was significantly increased, which the maximum water absorbency was enhanced 2.46 times when the composite polyacrylamide (PAM) was added compared to the control. The effects of ionic strength and sensitivity of pH on hydrogels were also studied. The modified hydrogels products with swelling ratio less sensitivity to the salinity as well as relative high swelling ration in salinity system were also obtained by adding PAM. Through the Fourier transform infrared spectroscopy (FTIR) characterizations, the crosslinking reaction mechanism and the structure of composite were proposed. In addition, the transmission electron microscopy (TEM) examinations showed that some composite materials elevated the physical crosslinked and connected channels density substantially.
A temporal linear stability analysis is carried out for a coflowing jet with two immiscible inviscid liquids under a uniform axial electric field. According to the electrical properties of the inner and outer liquids, four cases, i.e., IDOC (inner: dielectric; outer: conductor), ICOD (inner: conductor; outer: dielectric), ICOC (inner and outer: conductor), and IDOD (inner and outer: dielectric), are considered. The analytical dimensionless dispersion relation is derived for both axisymmetric and nonaxisymmetric perturbations and is solved for axisymmetric ones. Three unstable modes, i.e., the paravaricose, parasinuous and transitional modes, are identified in the Rayleigh regime. The influences of the axial electric field, liquid electrical properties, and Weber number are studied at length. The results show that the axial electric field has a generally stabilizing effect on the unstable modes. The effects of the liquid electrical properties are quite different but all great for each case. The change of dominant mode is detected with the variation of the electric field intensity, electrical properties or Weber number. It is found that the parasinuous instability is the easiest to realize in IDOC. And the comparison with the experiment validates that the parasinuous mode is predominant in coaxial electrospray.
Biocompatible, biodegradable and stimuli-responsive nanomaterials can be used as drug carriers and to achieve controlled drug delivery, which is crucial for treating tumors and lowering drug side effects. Calcium phosphate (CaP) nanoparticles and poly(acrylic acid) (PAA) hydrogels can be used as biocompatible and pH-responsive drug carriers. In this study, based on the ultrasound effect, PAA/CaP hybrid nanogels (approximately 100nm, PDI<0.2) are obtained via the cross-linking of CaP nanoparticles and PAA molecules between the Ca ions and -COOH groups. The PAA/CaP hybrid nanogels show good stability in biological media as well as no hemolysis and no cytotoxicity to L02 cells. Moreover, the PAA/CaP hybrid nanogels display an enhanced loading capacity (approximately 32%) for doxorubicin hydrochloride (DOX) compared to pure CaP nanoparticles (approximately 7.5%) and a pH-controlled drug release due to their dissolution in acidic environment. DOX can be delivered into cancer cells by the PAA/CaP hybrid nanogels, which show an inhibitory effect comparable to that of free DOX, although the inhibitory effect is delayed due to the slow release of DOX from the carriers. In vivo, the PAA/CaP hybrid nanogels cannot avoid the capture by the reticuloendothelial system; however, they show passive tumor targeting ability. In brief, the biocompatible, biodegradable and pH-responsive PAA/CaP hybrid nanogels have the potential to act as drug carriers for controlled drug release.
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