A Survey of Positioning Systems Using Visible LED Lights

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe

Antioxidant activity of maillard reaction products from lysine-glucose model system as related to optical property and copper (II) binding ability

Maillard reaction (MR) was carried out in L-lysine-D-glucose (Lys-Glu) model system heated at 120°C for 0 to 10 h without pH control. Optical property (UV-Vis absorbance and fluorescence) development of MR was monitored. Antioxidant activity of maillard reaction products (MRPs) was investigated by a series of in vitro tests. The UV-Vis absorbance zero and first-order derivative spectrophotometric was utilized to study the metal-binding property and chelating effect of different fractions of MRPs. MRPs had reducing power, strong free radical-scavenging activity and copper (II)-binding ability. The antioxidant activity of MRPs related well with the UV-Vis absorbance properties of maillard rection. Cu2+-binding to MRPs caused the electronic rearrangement in UV-Vis absorbance intermediates, but had no effect on the chromophore structure in brown polymers. The UV-Vis absorbance compounds were responsible to the reducing power and radical-scavenging activity. The fractions of low molecular weight MRPs showed effective metal-chelating ability.Key words: Maillard reaction products, antioxidant activity, metal-chelating effect, optical properties

Implications of new data in charmless B decays

Based on the latest experimental data of $B \to \pi\pi$ and $\pi K$ modes, a model-independent analytical analysis is presented. The CP-averaged branching ratio difference $\Delta R = R_c - R_n$ in $B\to \pi K$ decays with $R_c = 2Br(\pi^0K^-)/Br(\pi^-\bar{K}^0)$ and $R_n =Br(\pi^+K^-)/2Br(\pi^0\bar{K}^0)$ is reduced though it remains larger than the prediction from the standard model(SM) as both measured $R_n$ and $R_c$ are enhanced, which indicates that a room for new physics becomes smaller. The present data of $\pi\pi$ decay reduce the ratio $|C/T|$ from the previous value of $|C/T|\simeq 0.8$ to $|C/T| \simeq 0.65$, which is still larger than the theoretical estimations based on QCD factorization and pQCD. Within SM and flavor SU(3) symmetry, the current $\pi K$ data also diminish the ratio $|C'/T'|$ from the previous value $|C'/T'| \simeq 2$ to $|C'/T'| \simeq 1.16$ with a large strong phase $\delta_{C'} \simeq -2.65$, while its value remains much larger than the one extracted from the $\pi \pi$ modes. The direct CP violation $A_{CP}(\pi^0\bar{K}^0)$ is predicted to be $A_{CP}(\pi^0\bar{K}^0) = -0.15\pm0.03$, which is consistent with the present data. Two kinds of new effects in both strong and weak phases of the electroweak penguin diagram are considered. It is found that both cases can reduce the ratio to $|C'/T'| = 0.40\sim 0.80$ and lead to roughly the same predictions for CP violation in $\pi^0 K^0$.Comment: 13 pages, 4 figure

Parametric study of cavity length and mirror reflectivity in ultralow threshold quantum well InGaAs/AlGaAs lasers

Record low CW threshold currents of 16 μA at-room temperature and 21 μA at cryogenic temperature have been demonstrated in buried heterostructure strained layer, single quantum well InGaAs/AlGaAs lasers with a short cavity length and high reflectivity coatings

In vitro Anti-Gastric Tumor Activities and Possible Mechanisms of Action of Paederosidic Acid from Paederia scandens (Lour) Merrill

Purpose: To evaluate the anti-tumor activity and explore the possible mechanisms of action of paederosidic acid isolated from Paederia scandens (Lour.) Merrill.Methods: Paederosidic acid (PA) was isolated from P. scandens and identified by spectroscopic methods. The cytotoxic effects of PA in gastric cancer cell lines (MGC-803, BGC-823, and SGC-7901 cells) were assayed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT). Apoptosis of PA in SGC-7901 cells was evaluated by DAPI staining. To investigate the possible mechanisms of apoptosis, the effect of PA on C-caspase-3, C-caspase-9, Bcl-2 and Bax expressions in SGC-7901 cells were assayed by Western blot analysis.Results: PA exerted significant inhibitory effects on MGC-803, BGC-823, and SGC-7901 cells with 50 % inhibitory concentration (IC50) values of 42.2, 43.7, and 30.5 μM, respectively, and in a concentration-dependent manner. Subsequently, SGC-7901 cells were selected for further studies. After treatment with PA, obvious condensation of the nucleus was observed in fluorescence photomicrographs, which is a  characteristic of apoptosis. In addition, caspase-3, caspase-9 proteins and Bax were significantly  up-regulated (p < 0.05), whereas Bcl-2 was significantly down-regulated (p < 0.05) by PA in a concentration-dependent  manner.Conclusion: PA has significant anti-tumor activity on SGC-7901 cells in vitro, and the possible mechanism of action may be related to PA-induced apoptosis via mitochondria-mediated apoptosis pathway.Keywords: Paederosidic acid, Paederia scandens, Anti-tumor activity, Apoptosis, Gastric cance

Very High Modulation Efficiency of Ultralow Threshold Current Single Quantum Well InGaAs Lasers

A record high current modulation efficiency of 5 GHz/[sqrt](mA) has been demonstrated in an ultralow threshold strained layer single quantum well InGaAs laser

Exclusive B→PVB \to PV Decays and CP Violation in the General two-Higgs-doublet Model

We calculate all the branching ratios and direct CP violations of $B \to PV$ decays in a most general two-Higgs-doublet model with spontaneous CP violation. As the model has rich CP-violating sources, it is shown that the new physics effects to direct CP violations and branching ratios in some channels can be significant when adopting the generalized factorization approach to evaluate the hadronic matrix elements, which provides good signals for probing new physics beyond the SM in the future B experiments.Comment: 21 page