Petroporphyrins were enriched and purified from atmospheric residues of two typical heavy oils, Canadian oil sand bitumen (OSAR, Ni: 80 ppm, V: 190 ppm, S: 3.97 wt%) and Chinese Liaohe heavy oil (LHAR, Ni: 68.7 ppm, V: 1.81 ppm, S: 0.36 wt%) by silica gel chromatography. The separation and purification were confirmed by atomic absorption spectroscopy (AAS) combined with UV-vis spectroscopy, and the petroporphyrins were characterized by positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Vanadyl and nickel porphyrins in OSAR are simultaneously identified by mass measurement and isotopic fine structure. Vanadyl porphyrins with structures of N 4 VO, N 4 VO 2 and N 4 VOS are all detected as protonated analyte ([M+H] + ). Both molecular ion (M +• ) and analyte ([M+H] + ) as well as their corresponding isotopes are observed for N 4 Ni porphyrins in OSAR and LHAR with an average mass resolving power of over 400 000 (m/∆m 50% ). This is rarely detected by FT-ICR MS using ESI technique previously. Formation of molecular ion can be attributed to the low oxidation potential of nickel porphyrins, effect of oil matrix on the solution conductivity and the relatively low flow rate of solution into the capillary. Three more highly unsaturated types of N 4 VO porphyrins were identified in addition to the six well-documented structures. Compared to N 4 VO porphyrins, N 4 VOS porphyrins present higher DBE ranging from 21 to 27 while N 4 VO 2 porphyrins show lower DBE ranging from 18 to 20 and narrower carbon number distribution, suggesting possible different origins of sulfur (pyrolysis of kerogen) and oxygen (diagenesis of chlorophyills). Ni/V and ratio of relative abundance of ETIO porphyrins to DPEP porphyrins (∑ETIO/∑DPEP) for nickel porphyrins indicate that Liaohe oil and Canadian oil sand bitumen are continental and marine sediment, respectively, and Liaohe oil has a higher maturity.Enrichment by the simple chromatographic method facilitates the mass spectral identification of nickel porphyrins even for heavy residue with low content of nickel and high content of sulfur.

The pseudolite system is a good alternative for indoor positioning systems due to its large coverage area and accurate positioning solution. However, for common Global Positioning System (GPS) receivers, the pseudolite system requires some modifications of the user terminals. To solve the problem, this paper proposes a new pseudolite-based indoor positioning system architecture. The main idea is to receive real-world GPS signals, repeat each satellite signal and transmit those using indoor transmitting antennas. The transmitted GPS-like signal can be processed (signal acquisition and tracking, navigation data decoding) by the general receiver and thus no hardware-level modification on the receiver is required. In addition, all Tx can be synchronized with each other since one single clock is used in Rx/Tx. The proposed system is simulated using a software GPS receiver. The simulation results show the indoor positioning system is able to provide high accurate horizontal positioning in both static and dynamic situations.

No abstract

In the present study, the occurrence and characteristics of equatorial plasma bubble (EPB) has been analyzed using the GPS data from continuously operating reference stations network over Hong Kong during 2001–2012. The analysis found maximum EPB occurrences during the equinoctial months and minimum EPB occurrences during the December solstice throughout 2001–2012 except during the solar minimum in 2007–2009. The maximum EPB occurrences were observed in June solstice during 2007–2008, whereas for 2009, EPB occurrences were quite higher for June solstice but slightly smaller than the March equinox. The seasonal maximum in EPB occurrences have been discussed in terms of plasma density seed perturbation caused by gravity waves as well as the post sunset F‐layer rise due to the pre‐reversal enhancement of zonal electric field. Generally, EPB occurrences are found to be more prominent during nighttime hours (19:00–24:00 h) than daytime hours. The day and nighttime EPB occurrences were inferred and found to vary linearly with solar activity and have an annual correlation coefficient (R) of ~ 0.92 with F10.7 cm solar flux and ~0.88 with sunspot number. Moreover, the impact of solar activity on EPB occurrences is found to be dependent on seasons with maximum during the equinox (R = 0.80) and minimum during the summer season (R = 0.68). The detail study of EPB occurrences during two typical cases of geomagnetic storms on 6 November and 24 November 2001 found that the storm on 24 November triggered the EPB occurrence whereas storm on 6 November suppressed the EPB occurrence. The enhancement/suppression of EPB occurrences during storms periods is a consequence of a storm‐induced prompt penetration electric field as well as disturbance dynamo electric field effects associated with the main phase of the geomagnetic storm.