Adaptive Duty Cycling MAC Protocols Using Closed-Loop Control for Wireless Sensor Networks

The fundamental design goal of wireless sensor MAC protocols is to minimize unnecessary power consumption of the sensor nodes, because of its stringent resource constraints and ultra-power limitation. In existing MAC protocols in wireless sensor networks (WSNs), duty cycling, in which each node periodically cycles between the active and sleep states, has been introduced to reduce unnecessary energy consumption. Existing MAC schemes, however, use a fixed duty cycling regardless of multi-hop communication and traffic fluctuations. On the other hand, there is a tradeoff between energy efficiency and delay caused by duty cycling mechanism in multi-hop communication and existing MAC approaches only tend to improve energy efficiency with sacrificing data delivery delay. In this paper, we propose two different MAC schemes (ADS-MAC and ELA-MAC) using closed-loop control in order to achieve both energy savings and minimal delay in wireless sensor networks. The two proposed MAC schemes, which are synchronous and asynchronous approaches, respectively, utilize an adaptive timer and a successive preload frame with closed-loop control for adaptive duty cycling. As a result, the analysis and the simulation results show that our schemes outperform existing schemes in terms of energy efficiency and delivery delay

Effects of large-scale environment on the assembly history of central galaxies

We examine whether large-scale environment affects the mass assembly history of their central galaxies. To facilitate this, we constructed dark matter halo merger trees from a cosmological N-body simulation and calculated the formation and evolution of galaxies using a semi-analytic method. We confirm earlier results that smaller halos show a notable difference in formation time with a mild dependence on large-scale environment. However, using a semi-analytic model, we found that on average the growth rate of the stellar mass of central galaxies is largely insensitive to large-scale environment. Although our results show that the star formation rate (SFR) and the stellar mass of central galaxies in smaller halos are slightly affected by the assembly bias of halos, those galaxies are faint, and the difference in the SFR is minute, and therefore it is challenging to detect it in real galaxies given the current observational accuracy. Future galaxy surveys, such as the BigBOSS experiment and the Large Synoptic Survey Telescope, which are expected to provide observational data for fainter objects, will provide a chance to test our model predictions.Comment: 7 pages, 5 figure

A theoretical model for predicting Schottky-barrier height of the nanostructured silicide-silicon junction

ABSTRACT In this work, we have performed the first-principles calculations to investigate the Schottky barrier height (SBH) of various nanostructured silicide-silicon junctions. As for the silicides, PtSi, NiSi, TiSi2, and YSi2 have been used. We find that EFiF = EFi – EF, where EFi and EF are the intrinsic Fermi level of the semiconductor part and the Fermi level of the junction, respectively, is unchanged by nanostructuring. From this finding, we suggest a model, a symmetric increase of the SBH (SI) model, to properly predict SBHs of nanostructured silicide-silicon junctions. We also suggest two measurable quantities for the experimental validation of our model. The effect of our SI model applied to nanostructures such as nanowires and ultra-thin-bodies is compared with that of the widely used previous SBH model

The role of financial incentives in the treatment of children and adolescents infected with human immunodeficiency virus

Adherence to antiretroviral therapy (ART) is one of the most important issues in pediatric patients living with Human Immunodeficiency Virus (HIV). Combined with the fact that young patients face a large array of adherence barriers, interventions that can increase adherence are of great interest. Financial incentives (FIs) are a novel approach in pediatric HIV settings, and have not been studied previously in this disease for this age group. Thus, we sought to evaluate the effects FIs had in helping pediatric HIV patients achieve and maintain virologic suppression (VS). Furthermore, a post-incentive survey was administered to evaluate the self-perceived effects of FIs. In our study, FIs were not associated with achieving VS among pediatric and adolescent patients. The post-incentive survey has demonstrated many aspects of patients' and guardians' perceptions of FIs that should be considered in future FI studies. First, it was likely that patients who effectively grasped the concept of financial reward were most positively influenced by FIs. Second, the study data suggested that FIs may be contra-effective to those patients who report strong emotional responses to negative outcomes. Further and more comprehensive studies are required to fully characterize these effects

Ultrahigh areal number density solid-state on-chip microsupercapacitors via electrohydrodynamic jet printing

Microsupercapacitors (MSCs) have garnered considerable attention as a promising power source for microelectronics and miniaturized portable/wearable devices. However, their practical application has been hindered by the manufacturing complexity and dimensional limits. Here, we develop a new class of ultrahigh areal number density solid-state MSCs (UHD SS-MSCs) on a chip via electrohydrodynamic (EHD) jet printing. This is, to the best of our knowledge, the first study to exploit EHD jet printing in the MSCs. The activated carbon-based electrode inks are EHD jet-printed, creating interdigitated electrodes with fine feature sizes. Subsequently, a drying-free, ultraviolet-cured solid-state gel electrolyte is introduced to ensure electrochemical isolation between the SS-MSCs, enabling dense SS-MSC integration with on-demand (in-series/in-parallel) cell connection on a chip. The resulting on-chip UHD SS-MSCs exhibit exceptional areal number density [36 unit cells integrated on a chip (area = 8.0 mm x 8.2 mm), 54.9 cells cm(-2)] and areal operating voltage (65.9 V cm(-2))