Detecting Hot Road Mobility of Vehicular Ad Hoc Networks

Vehicular Ad Hoc Networks (VANETs) can provide value-added services to both drivers and passengers with on-board vehicular communication systems. Node mobility and volatile wireless connection in VANETs affect inter-contact time (T _I ) between mobile nodes, which greatly degrades the performance of vehicular applications. Nevertheless, the node spatial distribution in VANETs is another important factor especially in real applications. It positively affects the inter-contact time of vehicular nodes. By leveraging it, we can significantly improve the performance of data transmissions and inter-vehicle communication. To this end, we investigate the data collected from around 4,000 taxisin Shanghai and propose in this paper an efficient hot road mobility model. We find that most taxis distribute on some hot roads, which makes the node spatial distribution follow the power law. Based on this observation, we propose the concepts of indirect contact and heterogeneous inter-contact time (T _H ) to reveal how hot roads can change the distribution of inter-contact time. We find that the tail distribution of T _H also appears the power law, and both node spatial distribution and T _H distribution decay at least as the power law. We further propose a model for detecting vehicle mobility in hot roads, which can generates synthetic traces that captures both spatial and temporal features of nodes in VANETs.     

Determination of Formaldehyde Traces in Fabric and in Indoor Air by a Kinetic Fluorimetric Method

A simple and sensitive kinetic fluorimetric method is reported for the determination of trace amount of formaldehyde. The proposed method is based on the catalytic effect of formaldehyde on the oxidation reaction of rhodamine B with potassium chlorate in sulfuric acid solution. Formaldehyde in the range of 0.020-0.340 µg/mL can be determined with a limit of detection of 5.73 ng/mL. The method has been used to determine trace formaldehyde in fabric and in indoor air. The results thus obtained show good agreement with those determined by acetyl acetone method.     

Low threshold melt-processed two-photon organic surface emitting upconversion lasers

Herein, a low threshold, wavelength-tunable, compact, two-photon pumped upconversion laser is presented. The surface emitting lasers are composed of melt-processed 1,4-bis[2-[4-[N,N-di(p-totyl)amino]phenyl]vinyl]benzene (DADSB) as active media and two designed distributed bragg reflectors. The melting fabrication process is very simple, and the lasing threshold is as low as 150 μJ cm^?2 pulse^?1, when pumped by a Ti:sapphire amplifier operating at 800 nm with a 150 fs pulse width. To the best of our knowledge, it is one of the lowest values for two-photon lasers. Lasing from multimode to single-mode oscillation is demonstrated. Tunable single mode oscillation was obtained at wavelength from 514 nm to 523 nm with a spectral width of less than 0.2 nm.     

The high response organic ultraviolet photodetectors based on 2-TNATA as donor

Organic ultraviolet photodetectors (OUV-PDs) were fabricated utilizing 2-TNATA as an electron donor with Bphen and TPBi as electron acceptors. A high sensitivity of OUV-PDs to UV light was obtained in the range of 300–420 nm. The optimized OUV-PDs composed of Bphen as the acceptor offered a photocurrent density up to 336 µA/cm² at ?8 V with 365 nm UV light at a power of 1.2 mW/cm². The high response is attributed to the excellent electron transport ability of Bphen and the matched energy level between 2-TNATA and Bphen.     

Catalytic enantioselective synthesis of optically active α-hydroxyl-β,γ-unsaturated acid esters as novel side chains of cerebrosides

Six optically active α-hydroxyl-β,γ-unsaturated acid esters 1a to 1f were synthesised, and they are significant moieties of the cerebrosides. The chiral intermediate alkynol 4 prepared by catalytic asymmetric addition had 99% ee, and which was converted into the target compounds 1a to 1f with high enantiomeric purity.     

Measurements of charge in heated water

In the literature there are reports of static charges appearing with physical (i.e., phase and temperature) changes of water. One of the purposes of the present report is to refine the measurement of charge in heated water. The experiments described in this report confirm the reported phenomenon by comparing the different amounts of charge produced when different amounts of water are heated to the same temperature and in the same setup. When charge differential is correlated to water differential, the source of charge is better isolated to the change in water temperature rather than to any other possible source.