Assessing the damming effects on runoff using a multiple linear regression model: A case study of the Manwan Dam on the Lancang River

AbstractThe Lancang River in Yunnan Province, with a length of 1170km and a 1780-m drop from northwest to southeast, is the most controversial river in southwest China because 14 cascade hydropower stations have been planned on the main waterway. The Manwan Dam, the first of the 14 dams, began operating in 1993, and the associated downstream runoff may have been affected by its construction. To assess this impact, we first investigated the relationships between monthly runoff observed from the Gajiu station and meteorological data obtained from four meteorological gauging stations with a time-lag of 0-3 months over the pre-dam period (1957-2000). Second, we established and validated a multiple linear regression equation employing monthly meteorological and hydrological data during the pre-dam period. Finally, we simulated the monthly runoff after dam construction (1993-2000) using the established equations and assessed the impact of dam construction on runoff by comparing the observed actual monthly runoff with the simulated monthly runoff. Our results suggested a very high hydro-meteorological correlation for the pre-dam period, which opened up the possibility of runoff forecasting. Further, the multiple linear regression equation displayed good simulation performance as coefficient of determination (R2) and the Nash-Suttcliffe coefficient (NS) reached 0.84 and 0.82 respectively. By comparing the observed and the predicted monthly runoff, we found that construction of the Manwan Dam caused a visible disturbance on monthly runoff that, with the disturbance value, displayed a multi-peak fluctuation of up-down variation in the annual hydrologic regime circl

Simple Memristive SPICE Macro-Models and Reconfigurability in Filter and Antenna

Simple current- and voltage-controlled memristive circuit macro-models using SPICE are proposed to capture the nonlinear hysteresis loop behaviors in this paper. Different current-voltage characteristics are investigated by applying sinusoidal-wave, triangular-wave and square-wave source, respectively. Furthermore, using finite-difference time-domain (FDTD) emulator incorporated with a SPICE circuit solver, the current- or voltage-controlled memristive SPICE model is embedded into a planar microwave bandstop filter (BSF) and an ultra-wideband (UWB) monopole antenna, which connects two ends of the half-wavelength open-loop resonator and two sides of the U-slot in the radiating patch, respectively. The reconfigurability of the BSF and antenna notched band can be achieved by switching the states of the memristor

Thermal Fatigue Life Prediction of Ventilation Air Methane Oxidation Bed

Thermal flow-reversal oxidation is the main technology that can effectively reduce emissions of ventilation air methane. As the core component of coal mine ventilation oxidation devices, honeycomb ceramic oxidation beds play a decisive role in the functionality of these devices. The thermal fatigue properties of mullite ceramic – which is commonly used in oxidation beds – was tested in the present research. Then, the service life of the oxidation bed was predicted according to the intensity attenuation law and the thermal fatigue experimental data. The results of the fatigue experiment indicated that in general, the bending strength of mullite ceramics decreases as thermal shocks increase. At higher temperature differences, the bending strength decreased at greater rates. At the temperature differences between 600 and 800°C, the bending strength initially declined. Then, after reaching a certain value, it remained unchanged for a while before declining again. The results of the equation that was developed from intensity attenuation theory and the thermal fatigue experimental data indicate that the thermal fatigue life of an oxidation bed is about 1–8 months. The predicted result is consistent with actual working conditions

Study on Thermal Stress of Honeycomb Ceramic Regenerators with Different Parameters

In thermal flow-reversal reactor operations, honeycomb ceramic regenerators are exposed to thermal shock load. In this study, numerical simulations of the temperature and thermal stress distributions of honeycomb ceramic regenerators are carried out using the CFX software. Temperature variations with time are calculated first for honeycomb ceramic regenerators with holes of different shapes. Then, thermal stress distributions of regenerators are analyzed with different structural and operational parameters. The analyses show that the thermal stress of honeycomb ceramic regenerator depends on the shape of holes, porosity and wall thicknesses. This study provides a theoretical basis for optimization of honeycomb ceramic regenerators.При работе ядерного реверс-поточного реактора керамические сотовые регенераторы подвергаются действию термоударной нагрузки. С помощью программного обеспечения CFX проведено численное моделирование эпюр температуры и температурного напряжения керамических сотовых регенераторов. Исследовано изменение температур во времени для керамических сотовых регенераторов с отверстиями различной формы. Проанализированы эпюры температурного напряжения регенераторов с разными конструкционными и эксплуатационными параметрами. Установлено, что температурное напряжение керамического сотового регенератора зависит от формы отверстий, пористости и толщины стенок. Результаты данного исследования служат теоретической базой для оптимизации керамических сотовых регенераторов.При роботі ядерного реверс-потокового реактора керамічні стільникові регенератори зазнають дії термоударного навантаження. За допомогою програмного забезпечення СFX проведено чисельне моделювання епюр температури і температурного напруження керамічних стільникових регенераторів. Досліджено зміну температур у часі для керамічних стільникових регенераторів з отворами різної форми. Проаналізовано епюри температурного напруження регенераторів із різними конструкційними експлуатаційними параметрами. Установлено, що температурне напруження керамічного стільникового регенератора залежить від форми отвору, пористості і товщини стінок. Результати даного дослідження є теоретичною базою для оптимізації керамічних стільникових регенераторів

Thermodynamic properties of the d-density wave order in cuprates

We solve a popular effective Hamiltonian of competing $d$-density wave and d-wave superconductivity orders self-consistently at the mean-field level for a wide range of doping and temperature. The theory predicts a temperature dependence of the $d$-density wave order parameter seemingly inconsistent with the neutron scattering and $\mu$SR experiments of the cuprates. We further calculate thermodynamic quantities, such as chemical potential, entropy and specific heat. Their distinct features can be used to test the existence of the $d$-density wave order in cuprates.Comment: changed to 4 pages and 4 figures. More reference added. Accepted by Phys. Rev.

Quasiparticle vanishing driven by geometrical frustration

We investigate the single hole dynamics in the triangular t-J model. We study the structure of the hole spectral function, assuming the existence of a 120 magnetic Neel order. Within the self-consistent Born approximation (SCBA) there is a strong momentum and t sign dependence of the spectra, related to the underlying magnetic structure and the particle-hole asymmetry of the model. For positive t, and in the strong coupling regime, we find that the low energy quasiparticle excitations vanish outside the neighbourhood of the magnetic Goldstone modes; while for negative t the quasiparticle excitations are always well defined. In the latter, we also find resonances of magnetic origin whose energies scale as (J/t)^2/3 and can be identified with string excitations. We argue that this complex structure of the spectra is due to the subtle interplay between magnon-assisted and free hopping mechanisms. Our predictions are supported by an excellent agreement between the SCBA and the exact results on finite size clusters. We conclude that the conventional quasiparticle picture can be broken by the effect of geometrical magnetic frustration.Comment: 6 pages, 7 figures. Published versio