Diffuse export of nutrients under different land uses in the irrigation area of lower Beiyunhe River (China)

AbstractNon-point source pollution is serious in the agriculture watershed of China. Understanding the characteristics of rainfall-runoff from agriculture watershed can provide theoretical support for controlling non-point source pollution. In this study, we investigated runoff characteristics of eight indices (dissolved total N, NO3--N, NH4+-N, total phosphorus, dissolved total phosphorus, particulate phosphorus, total organic carbon, COD) from three types of land uses, including farmland, forest and village in the downstream irrigation area of the Beiyunhe River basin. The results showed that the event mean concentrations (EMCs) of total dissolved N in village, farmland and forestland were 17.81mg/L, 12.68mg/L and 3.14mg/L, respectively. EMC of total phosphorus in the order: farmland (0.44mg/L) > village (0.22mg/L) > forestland (0.17mg/L). EMC of COD in the order: farmland (45.07mg/L) > forestland (27.06mg/L) > village (18.03mg/L). The changes in the nutrients concentrations of the runoff water over a rainfall event indicated that the transports of the nutrients are similar among various land use types. The instantaneous concentrations of TN, NH4+-N, and NO3--N were high in the initial period of runoff, tend to decreasing with rainfall continuing, and increase in later period. Phosphorus concentration with time variation was not obvious among three land use types. The phosphorus species with high proportion in the total phosphorus was particle P (accounting for 75%) in forestland, dissolve P (79%) in farmland, and particle P (48%) and dissolve P (52%) in village. The curves of COD and TOC had been shown as high in the initial period of runoff, tending to increasing with rainfall continuing, and decrease in the later period. First-flush of all the indices were obvious in all three land use types with the rank of village > forestland > farmland. In village, all of the pollutions have taken place the phenomenon of first flush, while in farmland, pollutions tended to uniformly distribute or dilution throughout the storm event

Mixed rectilinear sources localization under unknown mutual coupling

In this paper, a novel rectilinearity-based localization method for mixed near-field (NF) and far-field (FF) sources is proposed under unknown mutual coupling. The multiple parameters including direction of arrival (DOA), range and mutual coupling coefficient (MCC) are decoupled, thus only three one-dimensional (1-D) spectral searches are required to estimate the parameters of mixed rectilinear signals successively. Furthermore, the closed-form deterministic Cramer–Rao bound (CRB) of the concerned problem is also derived. Simulation results are provided to demonstrate the effectiveness of the proposed method for the classification and localization of mixed rectilinear sources

Multiple Tiny Ectopic Sebaceous Glands Discovered Throughout Entire Esophageal Tract

A 45-year-old woman complaining of abdominal fullness was referred for endoscopic examination. She was a non-smoker and non-drinker. An endoscopic examination revealed the presence of more than 100 tiny, rounded, elevated, yellowish lesions < 0.5 mm in diameter scattered throughout the upper and lower esophagus. Based on the endoscopic examination results, her stomach manifested symptoms of mildly superficial gastritis. Histopathologic examination of the esophagus biopsy specimen revealed that some of the lobules of the cells displayed typical sebaceous differentiation covered by a squamous epithelium. No evidence of inflammatory reaction, hair follicles, or malignancy was found. The patient's blood and serum findings were unremarkable. Our final diagnosis was multiple tiny ectopic sebaceous glands in the esophagus. This is an interesting and rare case of esophageal sebaceous glands distributed throughout the entire esophagus. Because there were no esophageal symptoms or/and eating problems, the patient did not require endoscopic surgery or other treatment. Follow-up examinations were recommended at intervals between 6 months and 1 year. At the 2-year follow-up, an endoscopic examination revealed no change in the size or the number of the tiny ectopic esophageal sebaceous glands

Effective Dynamic Range in Measurements with Flash Analog-to-Digital Convertor

Flash Analog to Digital Convertor (FADC) is frequently used in nuclear and particle physics experiments, often as the major component in big multi-channel systems. The large data volume makes the optimization of operating parameters necessary. This article reports a study of a method to extend the dynamic range of an 8-bit FADC from the nominal $\rm{2^8}$ value. By comparing the integrated pulse area with that of a reference profile, good energy reconstruction and event identification can be achieved on saturated events from CsI(Tl) crystal scintillators. The effective dynamic range can be extended by at least 4 more bits. The algorithm is generic and is expected to be applicable to other detector systems with FADC readout.Comment: 19 pages, 1 table, 10 figure

Transient high-frequency impedance comparison-based protection for flexible DC distribution systems

Flexible direct current (DC) distribution systems have emerged as the development trend for future distribution grids. However, these systems are vulnerable to DC faults, rapid fault identification and faulted line selection method are required to enhance the security of the entire system. A novel transient high frequency impedance comparison based DC protection for flexible DC distribution systems is proposed in this paper. The control independent high frequency impedance model of power converter is also investigated. Based on this model, the proposed method identified the faulted lines by comparing high frequency impedance measurement differences. For DC bus with multiple branches, this technique minimizes the threshold calculation job, which is usually difficult to process for the transient value based protections. Strict synchronization of data is also not required for this method. The simulation model of four-terminal flexible DC distribution networks is built in PSCAD/EMTDC to verify the effectiveness of the proposed protection model. Simulation results prove that the protection is robust to fault transition resistances and the measurement noise

Measurement of the Intrinsic Radiopurity of Cs-137/U-235/U-238/Th-232 in CsI(Tl) Crystal Scintillators

The inorganic crystal scintillator CsI(Tl) has been used for low energy neutrino and Dark Matter experiments, where the intrinsic radiopurity is an issue of major importance. Low-background data were taken with a CsI(Tl) crystal array at the Kuo-Sheng Reactor Neutrino Laboratory. The pulse shape discrimination capabilities of the crystal, as well as the temporal and spatial correlations of the events, provide powerful means of measuring the intrinsic radiopurity of Cs-137 as well as the U-235, U-238 and Th-232 series. The event selection algorithms are described, with which the decay half-lives of Po-218, Po-214, Rn-220, Po-216 and Po-212 were derived. The measurements of the contamination levels, their concentration gradients with the crystal growth axis, and the uniformity among different crystal samples, are reported. The radiopurity in the U-238 and Th-232 series are comparable to those of the best reported in other crystal scintillators. Significant improvements in measurement sensitivities were achieved, similar to those from dedicated massive liquid scintillator detector. This analysis also provides in situ measurements of the detector performance parameters, such as spatial resolution, quenching factors, and data acquisition dead time.Comment: 28 pages, 12 figure

Nonadiabatic approach to dimerization gap and optical absorption coefficient of the Su-Schrieffer-Heeger model

An analytical nonadiabatic approach has been developed to study the dimerization gap and the optical absorption coefficient of the Su-Schrieffer-Heeger model where the electrons interact with dispersive quantum phonons. By investigating quantitatively the effects of quantum phonon fluctuations on the gap order and the optical responses in this system, we show that the dimerization gap is much more reduced by the quantum lattice fluctuations than the optical absorption coefficient is. The calculated optical absorption coefficient and the density of states do not have the inverse-square-root singularity, but have a peak above the gap edge and there exist a significant tail below the peak. The peak of optical absorption spectrum is not directly corresponding to the dimerized gap. Our results of the optical absorption coefficient agree well with those of the experiments in both the shape and the peak position of the optical absorption spectrum.Comment: 14 pages, 7 figures. to be published in PR

Studies of Prototype CsI(Tl) Crystal Scintillators for Low-Energy Neutrino Experiments

Crystal scintillators provide potential merits for the pursuit of low-energy low-background experiments. A CsI(Tl) scintillating crystal detector is being constructed to study low-energy neutrino physics at a nuclear reactor, while projects are underway to adopt this technique for dark matter searches. The choice of the geometrical parameters of the crystal modules, as well as the optimization of the read-out scheme, are the results of an R&D program. Crystals with 40 cm in length were developed. The detector requirements and the achieved performance of the prototypes are presented. Future prospects for this technique are discussed.Comment: 32 pages, 14 figure

Pulse Shape Discrimination Techniques in Scintillating CsI(Tl) Crystals

There are recent interests with CsI(Tl) scintillating crystals for Dark Matter experiments. The key merit is the capability to differentiate nuclear recoil (nr) signatures from the background $\beta / \gamma$-events due to ambient radioactivity on the basis of their different pulse shapes. One of the major experimental challenges is to perform such pulse shape analysis in the statistics-limited domain where the light output is close to the detection threshold. Using data derived from measurements with low energy $\gamma$'s and nuclear recoils due to neutron elastic scatterings, it was verified that the pulse shapes between $\beta / \gamma$-events are different. Several methods of pulse shape discrimination are studied, and their relative merits are compared. Full digitization of the pulse shapes is crucial to achieve good discrimination. Advanced software techniques with mean time, neural network and likelihood ratios give rise to satisfactory performance, and are superior to the conventional Double Charge method commonly applied at higher energies. Pulse shape discrimination becomes effective starting at a light yield of about 20 photo-electrons. This corresponds to a detection threshold of about 5 keV electron-equivalence energy, or 40$-$50 keV recoil kinetic energy, in realistic experiments.Comment: 20 pages, 7 figure

Search for Small Trans-Neptunian Objects by the TAOS Project

The Taiwan-America Occultation Survey (TAOS) aims to determine the number of small icy bodies in the outer reach of the Solar System by means of stellar occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9) telescopes have been installed at Lulin Observatory in Taiwan to simultaneously monitor some thousand of stars for such rare occultation events. Because a typical occultation event by a TNO a few km across will last for only a fraction of a second, fast photometry is necessary. A special CCD readout scheme has been devised to allow for stellar photometry taken a few times per second. Effective analysis pipelines have been developed to process stellar light curves and to correlate any possible flux changes among all telescopes. A few billion photometric measurements have been collected since the routine survey began in early 2005. Our preliminary result of a very low detection rate suggests a deficit of small TNOs down to a few km size, consistent with the extrapolation of some recent studies of larger (30--100 km) TNOs.Comment: 4 pages, 3 figures, IAU Symposium 23